mirrored file at http://SaturnianCosmology.Org/
For complete access to all the files of this collection
see http://SaturnianCosmology.org/search.php
==========================================================
*The Spirit and Opportunity landing sites as former Martian Poles*
*Abstract:*
Mars has many enigmatic features, such as Tharsis, Olympus Mons, Valles
Marineris, and Alba Patera. The volcanoes and Valles Marineris are huge
compared to the size of Mars with no apparent explanation for what made
them. In the theory outlined here the poles of Mars wandered through
history in response to 4 major impacts, Utopia, Isidis, Argyre, and
Hellas. As each impact occurred the large negative mass of the crater
tended to attract a rotational pole to it, and then later as large
volcanoes formed the mass of these tended to move to the Equator. The
combination of these events caused the poles to move over much of Mars
spreading water and ice signs along its path, and often leaving the rest
of Mars dry by comparison. This would account for how Mars shows so many
water and ice signs in some areas and appears so dry chemically in
others. In this paper only part of the polar path is shown, from south
of Valles Marineris the pole moved to Meridiani Planum where the
Opportunity rover is now. The opposite pole, which eventually became the
current North Pole moved from the area of the Isidis Crater to the area
around Gusev where the Spirit Rover is. We show how these areas are
geologically consistent with former poles, and how this polar path
implies a watery zone, possibly habitable for hundreds of millions of
years. This would be sufficient for life to possibly evolve
substantially if it existed at this time.
*Keywords: *astrobiology, crinoid, Gusev, Mars, Meridiani,, Opportunity,
polar, Spirit, water.
This theory originally came about from reading a paper by Sprenke and
Baker[1] <#_ftn1> on a proposed polar wander path on Mars. In the
process of examining this we accumulated published papers referring to
features along this path, and looked at whether features there were
consistent with having been on a pole.
Typically such features would be formed by water or ice, and the
terrain would be similar to known geology we see on the current poles.
This was contrasted with areas off this polar path, which typically were
much drier and ice free. Because the proposed polar path went back to
before Tharsis, Olympus Mons and Valles Marineris it became possible
this path was directed by the same forces that made these formations,
and much of the current Martian landscape. We found that virtually every
single paper published on Martian geology is consistent with this polar
wander path.
Because these large volcanoes have so much mass they tend to move to the
Equator, and so these could only form at certain times in the polar
wander. The polar path if correct then implies when these Mons formed
and also when large craters formed as their negative mass would tend to
attract the pole to them. Once the correct polar path is known, then
every other Martian feature with a significant impact on the
gravitational balance of Mars should only occur at certain points along
that path.
Because of space limitations and the serendipitous landing of the Rovers
on two former poles opposite each other, we have reproduced here the
middle part of the polar path. In the next paper we will show the
possible events before this section that formed Tharsis Montes, Olympus
Mons, Elysium Mons, and Valles Marineris. A following paper will carry
on after this one, with the Hellas impact attenuating the Martian
magnetic field and moving the pole to Hellas Crater, and then its
current position.
While it is not known if life exists on Mars the polar path strongly
implies a habitable zone existed around these poles as they wandered
across Mars, for hundreds of millions of years or more. The large
volcanoes of Tharsis, Elysium Mons, and Elysium Mons may have heated the
planet, as they are associated with parts of the polar path that
appeared to generate huge amounts of water.
In the three papers we will refer to 5 pole positions as being stable
for a time, and the polar movement between these positions. The current
pole positions we call Pole 5, and the polar movement from Pole 2 to
Pole 3 is discussed here, Pole 4 is near Hellas Crater. To follow this
path a good map of Mars is essential as many of the names are obscure.
If you Google and download “mola_regional.pdf”[2] <#_ftn2> this map
shows all the place names referred to here. For any image numbers,
placing the image number in a search engine and selecting the link from
msss.com is the fastest way to find them.
In this paper we concentrate on the movement from what we call the South
Polar Cap 2 position near Solis Planum (south of Valles Marineris) to
South Polar Cap 3 position at Meridiani Planum, shown in Figure 1. The
associated North Pole moved from the North Polar Cap 2 position around
Isidis Planitia eastward to near Lucus Planum as the corresponding North
Polar Cap 3. We call this North Polar Cap 3 because eventually it will
go to the current North Pole position. In this theory the Argyre impact
starts the polar wander from the second to the third position.
The path begins when the Pole is moving eastwards from the South Polar
Cap 2 position around Solis Planum, to north of Argyre Basin into
Margaritifer Terra and then east to Meridiani Planum, the site of South
Polar Cap 3. One should remember that a pole is very large in its
influence, so the exact position of the centre is often not significant.
For example the current poles are quite asymmetric in shape compared to
the rotational pole itself.
There is no direct evidence for the Polar Cap stabilizing or remaining
in Margaritifer Sinus for any great length in time along this route.
Figure 1 shows this path, South Polar Cap 2 to 3 is from Solis Planum to
Meridiani Planum.
*Figure 1: *The proposed polar wander path from Pole 2 to 3.
The large river networks in the Xanthe Terra and Margaritifer Sinus
areas imply the atmosphere at the time was much thicker, since water
would need a much higher air pressure than found today. A higher polar
obliquity may have also contributed to this. The axial tilt of Mars is
believed to change periodically over time, and when the angle is greater
the ice around the poles is thought to melt or sublimate much more.
This gives a possible habitable environment at this time, with abundant
water, heat from the Argyre impact, and higher air pressure. These water
signs persist all the way along the polar path to Meridiani Planum.
According to Grant[3] <#_ftn3> Margaritifer Sinus contains remnant high
valley densities, which is consistent with a moving pole and ice
melting. This area was resurfaced several times[4] <#_ftn4>, perhaps
from the subsequent volcanism related to the Argyre impact. Therefore,
ice may have partially vaporized, sublimed or melted, either due to
impacts, and/or due to subsurface heat from associated geothermal
activity. While Grant[5] <#_ftn5> believes some precipitation occurred,
most ground water would be consistent with a water table associated with
either a forming or sublimation/melting of an existing pole. The Parana
Valles[6] <#_ftn6> drainage system is particularly extensive. Therefore,
according to Grant[7] <#_ftn7>, groundwater discharge[8] <#_ftn8> must
have continued for some considerable time. The length of time referred
to would likely be sufficient for life, if present to evolve substantially.
Lewis and Aharonson[9] <#_ftn9> examine Holden Crater and the
distributary fan discovered in it. This area is near Argyre Crater and
implies liquid water was discharged from the Polar Cap nearby. Pondrelli
et al[10] <#_ftn10> also examine the area and how it connects the Argyre
Basin to the northern channels. Williams et al[11] <#_ftn11> report on
fans in Xanthe Terra, along the path of the Polar Cap.
Hynek et al[12] <#_ftn12> suggest that the fluvial resurfacing in this
area lasted for a period of some several hundred million years. A
combination of rainfall and sapping[13] <#_ftn13> appear likely, so
lakes may well have formed[14] <#_ftn14>. Polar wander may link the two
main theories of precipitation and sapping, hence explaining the
extensive valley networks[15] <#_ftn15>.
According to Nelson ice may have periodically melted. An examination of
Margaritifer Sinus, by Philips et al[16] <#_ftn16> concluded that much
of the Tharsis bulge was already in place before the drainage channels
formed. This is consistent with the general rise in elevation in the
area of Tharsis and Sinai Planum from the Argyre impact. At this time
Tharsis and Olympus Mons would have been growing after the Argyre
impact, and their extra weight would tend to move to the Equator. This
would have the effect of forcing South polar Cap 3 to move eastwards to
Meridiani Planum. This part of the polar path (and its antipodes, the
future North Pole) shows abundant evidence of water and ice. The area
around Margaritifer Sinus was plausibly a habitable zone and the Rover
Opportunity has now shown Meridiani Planum was a habitable zone. In
between these two there are enough water signs to imply this was a long
period of Martian history in which a habitable zone existed. It is not
known however if there was life there to take advantage of this.
During the late Noachian, Tharsis Rise was large enough to direct the
channels northward. Large amounts of material eroded from this area were
transported along these channels, most probably as a direct result of
basal water erosion during melting (and sublimation) as the Pole moved
north east of Valles Marineris[17] <#_ftn17> [18] <#_ftn18> towards
Margaritifer Sinus.
By the time the Polar Cap had moved north east of Valles Marineris water
and ice would have accumulated in it as the Polar Cap melted and moved
from the Argyre impact event, which may explain the paleolakes[19]
<#_ftn19> there. Carr[20] <#_ftn20> suggested that ground water flowed
into Valles Marineris and then into Chryse Planitia, forming lakes.
Rossi et al[21] <#_ftn21> believe there is good evidence of ice and
glaciation, consistent with a polar area adjacent to and south of the
Valles Marineris at that time. Glacial features in the area support this
interpretation.
Lunae Planum would also have received water from the moving and melting
of the pole. Shalbatana Valles originates in the chaos on Lunae Planum
(Greeley and Kuzmin[22] <#_ftn22>). Interestingly this would have
resulted from a probable impact basin that formed a catastrophic outflow.
Nelson and Greeley[23] <#_ftn23> discuss three major fluvial events in
Xanthe Terra, with indications of surface water flow. The first is a
broad sheetwash from the Valles Marineris area, perhaps coinciding with
the Argyre impact. Following this more extensive flooding occurred,
forming Shalbatana, Ravi, Simud, Tiu, and Areas Valles. This may
coincide with the pole migrating to Margaritifer Sinus. The majority of
surface water was sourced from chaos areas[24] <#_ftn24>. This gives a
direct link to the Argyre area and perhaps to that impact.
As we follow the polar wander, the fluvial-features seem to overprint
other terrain, so flooding may have continued as the Polar Cap migrated.
At the antipodes North Polar Cap 2 near the growing Elysium Mons started
to move eastward. This area has many signs of ice and water, for example
M0901921, M0905888, M0906366, M1001498, M1900226, M1902068, M2000840,
and M2000907. Again these photos from the MOC can be seen by placing the
image numbers in a search engine and selecting the link from msss.com.
Further signs can be seen in Martei Valles in M2001192, M2200885, and
SP238804. Lanagan et al[25] <#_ftn25> see evidence of fluvial flows
associated with Elysium Mons and lava flows in the area, and rootless
cones[26] <#_ftn26> also indicate ice in the area.
The new Odyssey results of subsurface ice[27] <#_ftn27> indicate a large
deposit on the equator in Babaea Terra. A second area of ice occurs on
the left edge of the map, just below the equator. This corresponds to
the location of the opposite North Polar Cap 3. According to Sprenke et
al the South Polar Cap moved in a curve to 0S 330W, almost into the
centre of the ice rich area at Meridiani Planum. We call this area South
Polar Cap 3. The geology and the geophysical data indicate icy areas on
opposite sides of the planet. When we calculate the radius of the planet
and adjust for any faulting, the result suggests that these areas were
almost certainly a polar pair. For each Polar Cap pair we
back-calculated the polar separations. The differences in diameters are
almost perfectly offset by the thickness of rift-like valleys and fault
movement and by assuming earth-like passive fault movement the polar age
relationships could be back calculated.
/ /
We believe the poles stabilised in these ice rich areas for a long time,
also with ample evidence of water signs. Thus the possible habitable
zone extends to the results we see from the Rovers and implies similar
chemistry and water signs may be found along this whole polar path from
Solis Planum.
Rift-like faults, glaciation, evidence of surface water, and even
volcanic activity tend to track the polar movement. The movement of Pole
2 to Pole 3 adds to approximately 150 degrees of longitudinal movement
so this is consistent with Tharsis forming near South Polar Cap 2 and
then moving nearly 180 degrees to the Equator, which pushed the poles
about 150 degrees eastward.
In this time Tharsis had to be growing so it would have been adding a
lot of heat to the atmosphere, and initially along with the newly formed
Argyre Crater parts of South Polar Cap 2 would have overlaid these hot
areas, melting water and CO2 if frozen. This would thicken the
atmosphere and perhaps create snow or precipitation away from the heat.
Tharsis and Argyre, with Elysium Mons then could have supplied the heat
for this potentially habitable zone to last so long. This would also
explain why Mars has so many water signs when it should have been too
cold for most of its history. The overall temperature of Mars probably
remained low, inhibiting the destruction of olivine even in the presence
of water.
South Polar Cap 3 assumed a position between the Argyre and Isidis
impact basins as each, being low gravity (low mass) would tend to be
close to this pole. When this occurred the Pole 3 positions would
attain a stable configuration. Tharsis was by this time near the Equator
and South Polar Cap 3 was near the two main negative masses of the
Argyre Crater and Isidis Crater, with Utopia Crater a lesser influence.
Interestingly, South Pole 3 coincides with an area of heavy Noachian
cratering[28] <#_ftn28> and the second cratered area corresponds well
with the opposite North Pole 3. One likely explanation is that the polar
ice protected the craters from erosion, and when they were exhumed from
the ice they remained in more pristine condition. Pole 3 seems to have
been stable for a long enough time for crater disparity. It also implies
at this time that the surface was being altered severely and other
craters were being buried or obliterated by lava flows.
Volcanism seems to follow the polar wander, so is either related to the
shock waves from impacts or is a late stage effect, occurring in
relation to degassing (geothermal activity) during faulting of polar
valleys. This would explain how volcanoes have apparently restarted in
Martian history and the surface is relatively young in parts.
Rift-like, passive, or strike-slip valleys would be thus be overprinted
by basal melting of icecaps and related sublimation. Most large
catastrophic flood (outburst) features occur adjacent to these poles so
may be triggered by increased geothermal heat. Pole 3 likely remained in
a stable location through this resurfacing.
These crater areas are linked into what is termed the Noachian age.
Thus, after the Argyre impact may be regarded as the Hesperian,
obliterating much of the Noachian terrain except for these parts
protected with polar ice. Some other areas with Noachian craters are
also found around Margaritifer Sinus, implying the Polar Cap may have
slowly moved and protected other areas for a time in its path. In a
later paper we will show a large northern ice sheet or ocean would have
sublimated after the Hellas impact, exposing the terrain referred to as
Amazonian. The two impacts then may have caused the features known as
Hesperian and Amazonian to form. This makes it difficult to estimates
times for these events as the polar path would have obscured and altered
crater counts.
In moving from Pole 2 to Pole 3, the polar ice closely follows and may
have formed or modified the dichotomy boundary. The main dichotomy
boundary is seen between 180 degrees west and 90 degrees west, which is
270 degrees or ¾ of a total possible boundary. The rest is taken up by
the land mass of Tharsis Montes, Syria Planum, etc.
South Polar Cap 2 moved from 12.7S 92.6W eastward to around 0S 330W,
which is approximately 122 degrees of longitudinal movement or
approximately 1/3 of the total great circle. The opposite pole migrated
from 12.7N 272.6W to 0S 150W, which is where the dichotomy boundary ends
against Olympus Mons, for a movement of 122 degrees. This makes 244
degrees of movement over a dichotomy boundary of 270 degrees as a polar
wander path. The rest can be explained by the width of the edge of South
Polar Cap 3 at 330W in Meridiani Planum, which makes it appear to extend
further east. Thus virtually the entire visible dichotomy boundary falls
on the same line as the movement of Pole 2 to Pole 3.
The Northern Lowlands represents a paradox. It is so large a negative
mass that it would likely prevent the Polar Caps moving along the path
proposed by Sprenke and Baker. Smith and Zuber[29] <#_ftn29> say that
Hellas Crater for example is only 10% of the volume of the Northern
plains. Thus its gravitational influence would be greater than either
Argyre or Hellas.
Therefore if this polar path is correct the Northern Lowlands was
partially covered in water or ice early in Martian history, neutralising
its negative mass. Oner et al[30] <#_ftn30> make some estimates of its
size. This would make the planet more balanced and not impede polar
wander. Indeed this ice or ocean had to exist for this polar wander to
occur, so proving polar wander proves the northern ice sheet existed.
The Northern Lowlands is so large a negative mass that the poles could
never have moved from their current position without water or ice to
fill in the low areas. Hence polar wander implies this water or ice
existed, and the shape of the ice rich areas at 60N shown by THEMIS
implies at least parts contained more ice at some point.
Early in the history of Mars the Northern Lowlands may have had other
impacts such as a Borealis impact lowering this area. Water and ice just
as on Earth would have migrated to the lower areas balancing the planet.
Over time the water would have smoothed out these ancient craters, as it
may have also done with Utopia Crater.
The polar wander path along the dichotomy boundary may have been on a
pre existing slope, altering its shape with ice and water erosion. A
Polar Cap moving on a slope like this would tend to have a runoff of
water heading north, accounting for the smoother surfaces in Acidalia,
Arcadis, Amazonis, and Elysium Planitia.
THEMIS[31] <#_ftn31> shows some evidence of such a runoff. Blue ice rich
areas extend from the polar path south west of Elysium Mons and north to
a huge ice deposit encircling the planet at 60N. This may have been part
of the ancient northern ice sheet or ocean. The heat from Elysium Mons
here would have been melting part of the moving polar cap and the water
flowed north to the main ocean or ice sheet. This THEMIS map should be
looked at in conjunction with the previously mentioned mola_regional.pdf.
Figure 2 shows a map of these ice rich areas. To make them clearer in
monochrome we have made the blue areas on the original appear white.
A is the approximate position of North polar Cap 2, where white ice
deposits can be seen. This trail moves to the right down to C, and on
the left edge of the map at J which would be North Polar Cap 3. North
east of A there is a trail of ice (more clear in the original map) shown
by B. This connects to the large ice deposit at H. In the center of the
ice trail at B is Elysium Mons. This implies that the heat from Elysium
Mons melted water here to make the runoff to H, and therefore that
Elysium Mons was hot when the pole was at A. On the northern end of this
trail is where Viking 2 landed, and also the best example of Martian
spider ravines[32] <#_ftn32> [33] <#_ftn33>outside of the current South
Pole. The large ice deposit at South Polar Cap 3 in Meridiani Planum is
shown at I, and F an ice trail linking it to a northern ice sheet.
This is consistent with the motion of the pole described here. At E we
see a large ice trail again, this time next to Olympus Mons and also
east towards Pavonis Mons[34] <#_ftn34>. This implies some of the ice of
North polar Cap 3 was melted by Olympus Mons and moved north to the
large ice area at G. E is also the location of Amazonis and Arcadia
Planitia which show signs of having been made smooth by water[35]
<#_ftn35>. Photos M1900946 and M1901546 show many volcanoes. These
probably formed partially or wholly in water. While this water may have
come from melting ice it may indicate the area was covered with ice or
water. Olympus Mons and Tharsis would have been still hot at this time,
which helps to date these events.
*Figure 3: the Northern lowlands*
Figure 3 shows dark areas on the Martian surface around the area of H in
Figure 2. This implies these dark areas may be associated with higher
amounts of ice. The trails of ice leading to these dark areas imply
there was liquid water, which implies some parts may have been a liquid
ocean at this time.
**
*Figure 4: Amazonis and Arcadia Planitia.*
Figure 4 shows the dark areas coinciding with Amazonis and Arcadia
Planitia.
*Figure 5: Map of Martian Iron at mid-latitudes.*
In Figure 5 a map of Iron on mars from the Odyssey Gamma Ray
Spectrometer[36] <#_ftn36> is shown. Here we have made the red, high
iron areas on the original map black to be seen more clearly. E
corresponds to Amazonis Planitia as a high Iron area. This is also
associated with darker soil, has many water and ice signs, and is
associated with the ice trail going northwards. So it is likely then
some of the Iron may have been leached from the ground by water melted
by Olympus Mons from North polar Cap 2. G shows the northern ice sheet
is also Iron rich and connected by water or ice trails.
F shows an iron rich area coinciding with an ice rich area. Between K
and B there is a trail of Iron from Meridiani Planum, or South polar Cap
3 up to Elysium Mons. This implies again that water from the pole moved
north and north east to the large ice areas at H. C shows a large Iron
deposit at North polar Cap 3.
It would be difficult for this Iron to occur in these areas due to
glaciation alone, so it is likely has some association with water. This
then implies a long-term northern ocean and ice sheet at the time
Olympus Mons, with heat provided along the major north-south faults by
Elysium and other Mons, at the same time the Pole moved from Position 2
to 3. The Opportunity area also has high iron (Fe). We know this is due
to pisolite. Hence, pisolite may have formed in at least some of these
regions.
As the Polar Cap moved along the dichotomy boundary from 2 to 3, new ice
would tend to form on the ground ahead and melt on the ground behind it
as the temperatures changed. The ice in front would tend to freeze into
the soil and create a similar situation to the current Pole 5 where
approximately half or more of the soil is ice. When this eventually
melted or sublimated the soil in the ice should have moved down the
slope and spread out. If there was a high enough air pressure this
should have created a seasonal water flow into Acidalia Planitia and
created the smooth surface. Amazonis Planitia is thought to be flat from
sedimentation or fluvial processes according to Head[37] <#_ftn37>.
Fuller et al[38] <#_ftn38> believe the Alba Patera area was resurfaced
volcanically and with fluvial sediments. A periodically higher obliquity
may have also created a water flow.
There are visible water channels in Lunae Planum, Xanthe Terra, and
Margaritifer Sinus, but these became less common as the Polar Cap moved
eastwards. The edges of the (green) elevation in MOLA maps[39] <#_ftn39>
along this path may indicate the edges of the permanent ice cap cutting
a flat platform. The primary erosion may have been caused by ice. Thus,
at this stage Martian temperatures and air pressure were possibly
dropping after the Argyre impact.
The ice deposit at South Polar Cap 3 abuts a cliff to the north, which
is an extension of the dichotomy boundary. This ice then implies that it
is connected to the creation of this cliff and by extension created the
cliff of the dichotomy boundary as the Polar Cap moved. As water ran
down the slope at South Pole 3 it would have eroded the ground, but
where the ground was permanently frozen the ground would have been
protected. This should then give a boundary to the north of the moving
Polar Cap where the ground slopes more. Note also how South Polar Cap 3
also has an ice path at approximately 345W connecting to the northern
ice sheet or ocean. Water and ice signs can be seen in narrow angle
images from Malin Space Science Systems, such as E0101857, E0300317,
E0401351, E0401589, E0503396, E1600085, E1801705, E2001051, E2100663,
and E2301402.
These ice paths imply the terrain at the time was conducive for water to
flow into the ice rich areas at 60N, which implies these ice rich areas
were formed substantially from water runoff themselves. If they were
solely formed from ice deposition there would be no need for them to
connect in apparent water paths. Much of this water may have moved in
subsurface aquifers, which would explain a lack of rivers connecting to
the ice rich area. Much of the water or ice had to previously exist
there for polar wander to occur. This can easily be tested by simulating
different depths of ice to these lower areas, and seeing if it balances
the planet sufficiently for the polar path shown here to occur.
North Polar Cap 3 includes the area around Gusev Crater and the Spirit
Rover site. Pablo et al[40] <#_ftn40> examined Atlantis Basin on this
previous Polar Cap and believe this contained an ancient paleolake. This
is consistent with the idea of a Polar Cap here, the area becoming
desiccated when the Polar Cap moved on. The heat sources may have been
from Olympus Mons, which would have been active at the time from the
Argyre impact. Spirit has found indications of repeated exposure to
water[41] <#_ftn41> [42] <#_ftn42>as well as more hematite concretions.
Irwin et al[43] <#_ftn43> describe Ma’adim Vallis as one of the largest
valleys on Mars, believed to have been carved from a large flood. This
amount of water on North Polar Cap 3 fits in well with the water signs
at South Polar Cap 3. Water from North polar Cap 3 may have moved
northwards into Arcadia Planitia.
Thomas-Keptra et al[44] <#_ftn44> propose carbonate disks in ALH84001
may have formed in an area similar to conditions found by the Rover
Opportunity, which would link possible life signs to these former poles.
This is also consistent with the idea of the water at the Rover
Opportunity site being from polar ice. Leask et al[45] <#_ftn45> examine
the Ravi Vallis and Aromatum Chaos areas and calculate the amount of
water that would have been involved. This would be the western edge of
South Polar Cap 3 and also represent an area the Polar Cap moved over.
Coleman[46] <#_ftn46> also examined this area and believes an ice
covered lake in Ganges Chasma recharged the aquifer source. This is also
consistent with the ice and water coming from South Polar Cap 3.
Woodworth-Lynas and Guigne[47] <#_ftn47> examine the Kasei Valles area
and believe water here was covered by ice floes. This is on the western
edge of South Polar Cap 3 and again implies large amounts of water
connected with the areas examined by Opportunity. The results of Holden
Crater, Aromatum Chaos and Kasei Valles imply the climate was warmer at
one stage for South Polar Cap 3, perhaps from increased obliquity[48]
<#_ftn48>.
Barlow and Dohm[49] <#_ftn49> examine Arabia Terra which is also on the
edge of South Polar Cap 3 and conclude a subsurface reservoir of ice and
liquid water existed here. Dohm et al[50] <#_ftn50> also indicate the
magnetic field may have been waning, consistent with the idea of the
Hellas impact later attenuating the magnetic field of Mars.
Arkani-Hamed and Boutin[51] <#_ftn51> plotted magnetic poles which agree
reasonably well with the movement of the Polar Cap along the dichotomy
boundary. The movement is roughly cycloidal, and from this it may be
possible to calculate how long it took the Polar Cap to move from South
Polar Cap 2 to 3. This assumes the magnetic Polar Cap may tend to move
around a given rotational Polar Cap position.
South Polar Cap 3 contains an area called the “Arabian Water-Rich Spot”
with 16% water (Mitrofanov et al[52] <#_ftn52>). Dalton et al[53]
<#_ftn53> also found evidence of water accumulation in the Flaugergues
drainage divide, which is also on South Polar Cap 3.
In each case, rift-like fault systems and hence lakes were all adjacent
to old polar caps. The valleys were then modified due to sublimation of
the icecaps and fluvial activity obscuring much of the faulting (as with
Chasma Australe).
If the degassing has a volcanic relationship as implied by the
polar-fault relationships, then SO2 may the major gas released with the
CO2 component being minor, related only to initial defrosting. This
seasonal defrosting would open pathways allowing degassing to occur.
The high iron and the sulfur content would thus result from volcanic
degassing. The Opportunity area is bounded by rift-like faults both
sides, and these look like they controlled the lake. The same Fe and
Sulfur relationships occur at Viking 2 (Utopia Planitia). In each case,
rift-fault systems and hence lakes were all adjacent to old polar caps.
In the Opportunity region, the pisolites (blue berries) form in two
ways. The first is by in situ replacement, possibly of titanium-rich
minerals by a lateralization-like process due to surface water. Other
pisolite overlay the Opportunity lake sediments. This may have formed by
shedding from an old iron deposit or may have formed like a bog iron
ore, after the polar cap moved. There is strong evidence[54] <#_ftn54>
at Opportunity that Meridiani Planum was wet and hospitable for life.
The water would likely be from the polar cap and implying an environment
hospitable to life along the whole polar path.
Siltstones may have formed in lakes and oceans adjacent to polar caps.
Some of these may have been carbonate rich (perhaps varves) at the time.
Thus, the icecap formed, then the rift valleys formed, degassing and
volcanism followed. The lakes may have existed in equilibrium with the
icecaps so a stable hydrological system must have existed, at least near
this polar pair.
Many of the rifts and major normal and strike slip faults of mars occur
adjacent to the polar caps. Thus, the crust has preferentially fractured
in polar regions. Degassing would occur due to increased geothermal
activity near hot spots or fractures in the mars crust.
The gases given off would be: CH_4 , SO_2 , SO_3 , CO, CO_2 , H_2 O.
Some of the minerals formed due to hydrothermal activity would be: FeS,
CuFeS, CuSO_4 .
SO_2 + 2H_2 O => H_2 SO_4 + H_2
H_2 SO_4 (sulfur) + CaCO_3 (Limestone/calcium-rich silts) => CaSO_4
(gypsum) + H_2 O + CO_2
The rocks at the Opportunity site indicate that the water then eroded
the gypsum crystals. The pisolites overlay the lake sediments, and
either formed during or most probably after the degassing event . The
gypsum in the lake sediment must therefore either be due to the
lakes/oceans drying up, or since the crystals crosscut the bedding may
well even be related to the degassing.
CaSO_4 (gypsum) + SiO_2 + H_2 O => Mud
In arctic conditions mud may not always form. The result may be very
fine silt, which would mix with or cover any near surface ice. If the
temperature were to increase the ice just below the surface melt and the
material would flow to create the mud-like surface features we see at
Opportunity. Even olivine would erode to fine dust particles. In
addition, any original pyrite related to hydrothermal activity would
eventually weather due to the existence of water.
2FeS (pyrite) + 3H_2 O => Fe_2 O_3 (pisolite) + 2H_2 S (rotten egg
gas) + 1/2H_2
The water would most likely then react to form sulfates or revert to ice
and be covered by or mixed with dust.
*Astrobiology*
It has been openly speculated at the recent Rover Press Conferences
about fossils[55] <#_ftn55> possibly being found at the Rover sites,
particularly at Meridiani. Also there have been some objects found which
some believe look like fossils. We will then examine the astrobiological
implications of this polar path.
The polar movement from Pole 2 to pole 3 as shown is accompanied by
regular discharges or water, flooding, and hematite deposits.
Hematite[56] <#_ftn56> has been found in the area of Pole 3, which is
consistent with the having water around a polar area. The area is
believed to have been recently exhumed, by Lane et al[57] <#_ftn57>
which is consistent with the Polar Cap moving and exposing this area.
According to Hynek Aram Chaos and Valles Marineris[58] <#_ftn58> [59]
<#_ftn59> also have hematite deposits, which is consistent with the path
of the moving Polar Cap from South Polar Cap 2 to 3 giving water to
create hematite. Hematite has been found by Spirit at Gusev Crater on
North Polar Cap 3. Catling and McKay[60] <#_ftn60> discuss possible
biological aspects of hematite deposits. Cockell[61] <#_ftn61> shows
that life could survive under snow, which would protect from UV rays and
still allow photosynthesis.
Hynek et al[62] <#_ftn62> say the erosion from water in Margaritifer
Sinus lasted up to several hundred million years. If the whole polar
wander path from Margaritifer Sinus to Meridiani Planum lasted only this
long then it implies a habitable area may then have existed on Mars for
long enough for life forms to have evolved in comparable time scales and
environments as on Earth. Even in Margaritifer Sinus it may have been
wet enough for long enough for life to evolve substantially. Life could
have stayed close enough to the volcanoes for warmth, and the polar path
implies at least Tharsis was hot for several hundred million years or more.
Opportunity[63] <#_ftn63> has found a volcanic rock almost identical
spectrographically to the Shergotty meteorite found on Earth. If
transfers of material were happening when Meridiani was a pole then it
implies life from Earth (or vice versa) may have been introduced by the
same mechanism along this polar wander path.
Several objects in particular seen at the Opportunity site seem to have
a resemblance to fossil shapes, such as crinoids. The fossil shapes may
be also explained by vughs forming during lateritization - but since
even skeptics agree they look like fossils, more
work is required to test this hypothesis.
Ausich et al[64] <#_ftn64> in their Figure 5 shows some shapes which can
be compared to Figures 6 and 7 in this paper. Aronson and Blake[65]
<#_ftn65> show similar shapes in Polychaetes. Radwanska and
Radwanski[66] <#_ftn66> show more similar examples.
*Figure 6*[67]* <#_ftn67>: *
*Figure 7*[68]* <#_ftn68>: *The top of the fossil like shape appears to
be beginning to branch in two. There appears to also be a tail like shape.
Schelble et al[69] <#_ftn69> discuss biological material often found
associated with hematite, similar to shapes seen by the Opportunity
Rover. Figure 8[70] <#_ftn70> shows a tubular shape reminiscent of a
fossil or cryptobiotic soil crusts.
*Figure 8 *
Krasnopolsky et al[71] <#_ftn71> have detected methane in the Martian
atmosphere which they believe is coming from the equatorial regions,
which is consistent with this polar wander path. Vittorio Formisano[72]
<#_ftn72> has also found methane, at 10.5 parts per billion. Mumma et
al[73] <#_ftn73> also found methane. On Earth methane is usually
associated with biological activity.
*Conclusions*
Geology along the polar path suggested by Sprenke and Baker is
consistent with polar ice and water. This section of the polar path
would have been initiated by the rise of Tharsis, and as Tharsis moved
to the Equator it forced the eventual South Pole eastward from Solis
Planum to Meridiani Planum.
Signs of water, ice erosion, and hematite follow the polar wander path.
Since the Opportunity Rover detected a potentially habitable
environment, this may have persisted during the entire polar wander from
Solis Planum and perhaps even earlier.
Estimates of the time taken to make this polar path are consistent with
the time needed for substantial evolution to have taken place in Earth’s
early history. If life existed on Mars at the start of this path, then
it is possible a habitable zone existed for most of not all of this time.
Earlier than this an ice sheet and ocean would have occupied parts of
the Northern Lowlands, in a shape consistent with water flows from the
heat around Olympus Mons and Elysium Mons. Water near the heat from
these volcanoes would be another potentially habitable zone for as long
as they supplied a heat source.
Objects have been found at the Opportunity site with shapes similar to
fossils. Methane emissions from the equatorial regions could be signs of
past or present life. The polar wander path links a large volume of
geological data suggesting that liquid water and the prerequisites for
life did exist on Mars and over a substantial period in time. Thus, if
life is not detected it may be a function of the measurement methods
used rather than life not having existed. Future missions to mars need
to be designed to help answer this more substantively.
------------------------------------------------------------------------
[1] <#_ftnref1> K. F. Sprenke and L. L. Baker (2000) “POLAR WANDERING
ON MARS?” LPSC XXXI 1930.pdf
[2] <#_ftnref2> Such as :
http://planetarynames.wr.usgs.gov/images/mola_regional.pdf
[3] <#_ftnref3> J. A. Grant (2001) “Valley Evolution in Margaritifer
Sinus, Mars” LPSC XXXII 1226.pdf.
“Introduction: The Margaritifer Sinus region of Mars preserves some of
the highest valley network densities on the planet [1-4]. Two large
northwest draining valley systems, Samara and Parana-Loire Valles, whose
associated basins cover an area exceeding 540,000 km2, dominate regional
drainage. These valley systems converge on Margaritifer Basin, a
confluence plain shared with the Uzboi-Holden-Ladon-Margaritifer Valles
meso-outflow system (UHLM) that drains northward from Argyre. Detailed
geologic and morphometric mapping of the Samara and Parana-Loire valley
systems confirms the timing of incisement and permits evaluation of
possible mechanisms for valley evolution [2, 5-8].”
[4] <#_ftnref4> Ibid.
“features in Margaritifer Sinus. Four resurfacing events that deposited
materials interpreted to be of mostly volcanic origin on the basis of
wrinkle ridges and occasionally lobate morphology followed formation of
these basins. The first three resurfacing events were
widespread and ended before evolution of the preserved valleys; the
first two occurred during early Noachian heavy bombardment [11] and the
second ended at an N5 age of 1400 (number of craters >5 km in diameter
per 1,000,000 km2). By contrast, the third resurfacing event began
during the middle Noachian (N5 of 500) and ceased during the late
Noachian (N5 of 300) coincident with waning highland volcanism [11].
Formation of Samara and Parana-Loire Valles, the UHLM system, infilling
of associated depositional sinks (e.g., Parana Basin at 12.50W, 22.50S),
and initial collapse of Margaritifer Chaos all occurred from the late
Noachian (N5 of 300) into the early Hesperian (N5 of 150). The last,
more localized resurfacing event lasted into the early and middle
Hesperian (N5 ages 200 to 70) and emplaced materials that embay valleys.
Nearly all area surfaces have been subsequently modified to varying
degree by eolian activity.”
[5] <#_ftnref5> Ibid.
“Model for Valley Evolution: A model for valley formation consistent
with these results involves mostly localized ground-water discharge
enabled by surface fed recharge. In this model, precipitation (rain or
snow) would be largely relegated to subsurface entry by high
surface-infiltration capacities. Discharge at exposed relief would be
controlled by occurrence of layers/ aquitards. Valley evolution would
have continued until draw-down of the water table following cessation
of precipitation, thereby resulting in a strong sapping overprint.
Martian valley formation by this process may best explain observed
morphometry. For example, the basin wide distribution of valleys (Fig.
1), low drainage density and ruggedness numbers, degree of integration,
and sediment volume in along-valley sinks may be difficult to
accommodate in a hypothesis involving ground-water discharge in the
absence of surface recharge. With surface-fed recharge, valley
distribution would be controlled mostly by the occurrence of layers/
aquitards.”
[6] <#_ftnref6> D. Williams (2003) “Parana Valles drainage system in
Margaritifer Sinus, Mars” NASA Goddard Space Flight Center. Image at:
http://nssdc.gsfc.nasa.gov/imgcat/html/object_page/vo1_084a47.html
[7] <#_ftnref7> John A. Grant (2001) “DRAINAGE EVOLUTION IN MARGARITIFER
SINUS, MARS” Paper No. 132-0 GSA Annual Meeting, Boston, Massachusetts
“Geologic mapping in Margaritifer Sinus, Mars, defines a complex history
of water transport, storage, and release that began in the late Noachian
and persisted into at least the mid-Hesperian. Collection, transport,
and discharge of the water from widely dispersed surfaces were
accomplished by systems of differing character flanking opposite sides
of the Chryse Trough. Drainage on the western side of the trough was
accommodated by the segmented Uzboi-Ladon-Margaritifer mesoscale outflow
system that heads in Argyre basin, drains approximately 9% of the
Martian surface, and alternately incises and fills as it crosses ancient
multi-ringed impact basins.”
[8] <#_ftnref8>March 9, 2000. Goddard Space Flight Centre “View inside
Mars reveals rapid cooling and buried channels” Top Story. Available
online at* * http://www.gsfc.nasa.gov/topstory/20000309mars.html
“The crustal structure accounts for the elevation of the Martian
northern lowlands, which controlled the northward flow of water early in
Martian history, producing a network of valleys and outflow channels.
The new gravity-field data suggest that the transport of water continued
far into the northern plains. The gravity shows features interpreted as
channels buried beneath the northern lowlands emanating from Valles
Marineris and the Chryse and Kasei Valles outflow regions.”
[9] <#_ftnref9> K. Lewis and O. Aharonson (2004) “Characterization of
the distributory fan in Holden NE Crater using stereo analysis” LPSC
XXXV 2083.pdf.
“*Introduction: *The recent discovery of a distributary fan in a large
crater northeast of Holden by Malin
and Edgett has been presented as evidence for persistent flow of water
on Mars [1]. With at least three
separate depositional lobes and a clearly layered structure, this
feature is so far unique among sedimentary
structures on Mars. This fan has been deposited by fluvial processes,
and then subsequently eroded back
from its original extent. This process has left behind an inverted
topography, with the floors of former channels standing above the
surrounding terrain. Several of the remnant channels in this formation
appear to display meandering curves, which is the strongest evidence for
a steady supply of water at this location.
Further, persistent flow raises the possibility that this feature was,
at one time, a lacustrine delta.”
[10] <#_ftnref10>M Pondrelli et al (2004) “Complex evolution of
Paleolacustrine systems on Mars: an example from the Holden Crater” LPSC
XXXV 1249.pdf
“*Introduction: *Lacustrine systems are extremely sensitive to
environmental fluctuations and, thus, they represent an ideal geological
setting to investigate for climatic changes. Among the putative Martian
paleolakes, the Holden crater (26S/326E) (Fig. 1) shows a richness of
fluvio-lacustrine features. The Holden crater is 130 km wide and lies on
Noachian rocks of the southern-cratered terrains [1]. The crater appears
to interrupt a fluvial system of Hesperian age [1] which likely
connected the Argyre basin to the northern chaos-outflow channels
system. The main valley, Uzboi Vallis, cuts the southern rim and
debouches into the crater. The Uzboi Vallis and Holden crater floors
have been previously mapped as same units of fluviolacustrine deposits
origin reworked by wind activity [2]. These deposits show a variety of
sedimentary and morphological differences at MOC and THEMIS scale.”
[11] <#_ftnref11> R.M.E. Williams et al (2004) “Young fans in an
equatorial crater in Xanthe Terra, Mars” LPSC XXXV 1415.pdf.
“*Introduction: *In recent years, the Mars Global Surveyor (MGS) Mars
Orbiter Camera (MOC)
investigation has largely focused on NASA’s Mars Exploration Program
“Follow the Water” theme. We report here on MOC narrow angle (NA) images
obtained in 2003 following observations from 1999 that show a specific,
un-named, ~60 km-diameter impact crater at an equatorial latitude
(7.6oN, 33.0oW) that exhibits well-preserved landforms similar in
planimetric form and morphology to alluvial fans of arid environments
such as the Mojave Desert of southern California. The principal question
is whether these fans represent the products of water and gravity-driven
alluvial sedimentation. The landforms in the Xanthe Terra crater are unique
among MOC images of martian impact craters, with the exception of some
features in middle latitude Hale Crater and its central peak (35.9°S,
36.6°W). The purpose of this paper is to present an initial, brief
description of these landforms and explore their implications.
…
Some of the channels display branching networks proximal to the fan
(Fig. 3). The channel networks display a third-order topology using
Horton’s ordering scheme. First-order tributaries of the channels that
feed the fans extend to the crest of local topographic highs. Locally,
the density of channels (total channel length per area of network) is
extremely high (preliminary value >500 km-1), comparable to terrestrial
values for much larger scale rivers in humid environments with highly
erodable substrates. In areas of high channel density, channels are
visible to the resolution limit of the MOC NA images.”
[12] <#_ftnref12> B. M. Hynek and R. J. Phillips (2001) “Evidence for
extensive denudation of the Martian highlands” Geology, 29, 407-410.
“Using high-resolution topographic data from the Mars Orbiter laser
altimeter (MOLA) instrument on the Mars Global Surveyor mission
(Smith et al., 1999), we have gathered evidence for a major fluvial
resurfacing event in the Martian highlands. We completed detailed
geomorphic mapping for the Margaritifer Sinus region (08–308S, 08–
308W), where resurfacing appears most evident. In addition, evidence
from adjacent areas suggests that this was not a localized event, but
one that affected at least 1 3 107 km2 (an area equivalent to the
European continent) of the cratered uplands. The topographic information
allows for the first time a separation of younger, low-standing
fluvially reworked terrains from older, high-standing erosional
remnants. The newly acquired MOLA data also allow the volume of eroded
material to be sensibly determined and minimum erosion rates to be
estimated. The erosional episode was limited in time to no more than
several hundred million years, and occurred ca. 4 Ga. The scale of the
processes involved strongly suggests, but does not demonstrate uniquely,
that precipitation must have played a major role in landscape denudation
in this region of Mars.”
[13] <#_ftnref13> Ibid.
[13] “Formation processes of valley networks are still controversial; the
debate is largely focused on the relative roles of surface runoff and
groundwater processes. In the mapped region, the morphology of the
valleys and associated networks (v-shaped profile, sinuous, high
density, and high valley order) and the observation that numerous
valleys originate near the tops of crater rims or hilltops (Fig. 3)
indicate that precipitation and surface runoff may have played a major
role in their formation. Some valleys show morphologies more consistent
with a groundwater-sapping origin (u-shaped profile, low density and
order, and alcove-like terminations), suggesting that subsurface water
was also important. Therefore, both precipitation and groundwater
certainly contributed to degradation in the Margaritifer Sinus region,
but the relative importance of each erosion mechanism is unclear. These
results are consistent with previous work completed on the south-central
part of our study area (Grant, 2000).”
http://ltpwww.gsfc.nasa.gov/tharsis/hynek.erosion.pdf
[14] <#_ftnref14> Ibid.
[14] “There is evidence for a large paleolake in the region (Parana basin;
22.58S, 12.58W, area ;33 000 km2) (Goldspiel and Squyres, 1991). The
depression contains hummocky interior deposits with interspersed smooth
terrain (Ni) that were emplaced contemporaneously with the extensive
denudation and valley network formation. A large number of valley
systems terminating at the proposed shoreline of Parana basin are
believed to have been sources for the paleolake (Goldspiel and
Squyres, 1991). The unit HNl contains a hematite spectral signature
and is interpreted to be sedimentary layers deposited from large-scale
water interactions (Christensen et al., 2000).”
[15] <#_ftnref15>B. Moomaw (2001) “Mars: A World of Varied
Catastrophes” MARSDAILY May 1, 2001
available online at
http://www.spacedaily.com/news/lunarplanet-2001-01a2.html
“J.A. Grant examined the valley networks in the Margaritifer Sinus
region, the area on Mars where they are most concentrated, and concluded
that they were indeed carved by "sapping" (tunneling by underground
water flows) rather than surface runoff -- but also that the only way
such a subsurface water supply could be adequately replenished was if
"widespread precipitation" in the form of rain or snow occurred in the
region and then seeped into Mars' porous ground.
B.M Hynek concluded from MGS' laser topography maps that the western
Arabia Terra ("Arabia Highlands"), an area the size of Europe, was so
eroded by surface rain that 3 million cubic km of its material was
gradually washed into Mars' low-altitude northern plains.
K.P. Harrison and R.E. Grimm examined the fact that the areas on Mars
where valley networks seem to be most concentrated are also those where
MGS' magnetic sensors -- to everyone's surprise -- found local magnetic
fields which seem to be areas where crustal iron minerals have been
permanently magnetized by Mars' long-vanished early magnetic field.
Since this most easily occurs when molten rock is exposed to a magnetic
field at the same time that it is rapidly cooled into solid form, the
obvious possibility is that rising flows of underground magma may have
collided in these areas with large amounts of groundwater kilometers
below the surface, providing a flow of geothermal hot springs for the
valley networks, and also cooling the magma quickly enough to "freeze" a
copy of Mars' magnetic field into the resulting solid rock before Mars'
magnetic field could reverse polarity (which, like Earth's, it probably
did every million years or less) and thus scramble the permanently
recorded "fossil" field.
D.M. Nelson examined the highlands south of the Elysium Basin -- through
which three especially big channels seem to have carried fluid for a
long period -- and concluded that the area showed signs of having
undergone repeated cycles of geological peace that would have allowed a
local layer of ground ice to build up, and episodes of moderate
volcanism just right to melt the accumulated ice and produce large water
flows into Elysium.” Bruce Moomaw “Mars: A World of Varied Catastrophes”
[16] <#_ftnref16>R. J. Phillips et al (2001) “Ancient Geodynamics and
Global-Scale Hydrology on Mars” SCIENCE VOL 291 30 MARCH 2001
“Valley networks were examined in detail (25) in Margaritifer Sinus, a
region on the flank of the Arabia bulge and in the Tharsis trough (Fig.
3B). Most formed on regions of relatively high topographic gradient on
the flanks of the trough. The majority (;85%) of
observed valley networks here likely formed in Late Noachian time,
between ;4.3 to 3.85 billion years ago (Ga) and ;3.8 to 3.50 Ga (26),
although the possibility exists that earlier valley networks in this
region were destroyed by a high impact flux or alternative erosion
mechanisms. Because many of these valley network orientations are
controlled by Tharsis-induced slopes, the Tharsis load must be largely
Noachian in age, which is consistent with inferences made earlier.
Superposition and sequence relationships indicate that
the valley networks whose azimuths are not explained by the model are
nevertheless contemporaneous with the Tharsis-controlled valley networks
(27). The formation of valley networks in Margaritifer Sinus is
intimately associated with a Late Noachian, large-scale erosion event on
the flanks of the Tharsis trough that stripped at least 1.5 3 106 km3 of
material from this area, leaving behind numerous mesas of Early and
Middle Noachian terrain (25).”
[17] <#_ftnref17> H. Frey
(2001)
Geodynamics “2001 The Year in Review” Annual Report of the Geodynamics
Branch, Goddard Space Flight Center.
“Figure 1 shows two recent magnetic maps of Mars derived using these
techniques. The anomalies have a pattern strongly suggestive of faulting
and perhaps offset along faults along a major tectonic structure. The
Vallis Marineris on Mars is a series of large, fault-bounded canyons
which have been compared with major rift structures on the Earth. The
pattern in the magnetic maps, especially the abrupt truncation of the
anomalies at the wall of the canyon, supports the idea that the Valles
Marineris canyon is a tectonic graben. The maps also suggest that highly
magnetic source rocks exist at the intersection of Coprates and Capri
Chasmata, on the northeast corner of the canyons, and there is a good
possibility that these magnetic rocks may be exposed along the fault
wall.”
[18] <#_ftnref18> M.E. Purucker et al (2001) LPSC XXXII 1865.pdf
“Interpretation of a magnetic map of the Valles Marineris region, Mars”.
available online at http://denali.gsfc.nasa.gov/terr_mag/abstract_mars.pdf
[19] <#_ftnref19> B. Murray [1999] “PALEOLAKE DEPOSITS IN CENTRAL VALLES
MARINERIS: A UNIQUE OPPORTUNITY FOR 2001” Second Mars Surveyor landing
site Workshop.
“Paleolake deposits have been mapped in Central Valles Marineris since
Mariner 9 and Viking
(McCauley, 1978; Nedell et al., 1988;Witbeck et al., 1991). Accordingly,
the region has been proposed as a priority target for landed payloads
intended to detect diagnostic mineral evidence of a permanent lake
environment, and, especially, biogenic signatures that could have
survived from such promising candidate Martian habitats. (eg, Murray, et
al, 1996; Yen, et al, 1999, Murray, et al, 1999). Just-released MOLA
data strongly buttress the hydrological case for longduration
ice-covered lakes there during Hesperian times at least.”
[20] <#_ftnref20> Ibid
“Carr (1996) suggested that ground water flowed from the Tharsis uplands
into the deep canyons of Valles Marineris before debouching onto Chryse
Planitia in the northern plains. Such a flow may have persisted for
billions of years, and is generally inferred to have maintained deep
lakes beneath which lacustrine sediments accumulated. Remnants of these
Hesperian Age lake deposits survive today as conspicuous layered strata
in Central Valles Marineris. Just published MOLA data (Smith, et al,
1999) confirm in detail this topographic trend and, most importantly,
prove that deep, permanent lakes did indeed exist, especially in Central
and Western Valles Marineris. Because the canyons in the Valles
Marineris are deeper than the probable ground water table at that
period, large portions of the canyons would have filled with water and
formed ice-covered lakes.”
[21] <#_ftnref21> A.P. Rossi et al (1999) “[46.03] Flow-like
features in Valles Marineris, Mars: Possible ice-driven creep
processes” 31st Annual Meeting of the DPS, October 1999 Session 46.
Mars Surface: Evidence of Change Posters .
“Recent high resolution MOC images have revealed the presence of
deformed impact craters on flow-like features characterized by
narrow bands of alternating light and dark material on the walls of
Valles Marineris. The maximum crater elongations are consistent with
the flow directions. Moreover the directions of these flows follow
the topography downslope. In some cases, the flows emanate from
cirque-like depressions, and the flows are divided by sharp ridges
similar to arête. These landforms have resemblance to (1)
alpine-type glacier morphology, including cirques, arêtes, and
glaciers containing medial moraines; and (2) Grand Canyon-type
sapping and mass wasting features. Certain aspects of the features
in Valles Marineris seem more consistent with the first hypothesis
involving a viscous rheology of the flows driven by ice-assisted
creep processes. This hypothesis includes direct analogies to
glaciers and rock glaciers. In the case of rock glaciers, flow is
produced by freeze-thaw and by internal deformation of ice cores or
lenses, whereas in the case of glaciers, movement occurs by internal
deformation plus basal sliding in some cases where the glacier is
melted at its bed. The amounts and roles of ice in the genesis of
the Martian glacier-type landforms in Valles Marineris are not clear
at this point. The population density of undeformed fresh impact
craters on these flows appears to be low compared with the
surrounding plateau areas. This may indicate relatively recent ages
of the flow processes.”
[22] <#_ftnref22> R. Greeley and R. Kuzmin (1999) “SHALBATANA VALLIS: A
POTENTIAL SITE FOR ANCIENT GROUND WATER” 2nd Mars Surveyor landing site
workshop, SUNY/Buffalo, 43-44
available online at
http://www.aas.org/publications/baas/v31n4/dps99/158.htm
“The channel is unusual because it appears to represent a single outflow
initiated by a large impact. This impact could have excavated materials
from the Martian crust from depths of several kilometers, apparently
“tapping” the aquifer system leading to catastrophic
flooding to form the channel. Ejecta from the Noachian impact crater
[6, 7] is preserved NW-W and SE from the source area. The width of
Shalbatana Vallis near its source is about 50 km and then it
continues 500 km NE as a sinuous, narrow channel of nearly constant
width (10 -20 km cross) and depth (~2 km). The channel then becomes
wider (40-50 km), bifurcates, and enters Simud Vallis [7].”
[23] <#_ftnref23> D.M. Nelson and R. Greeley (1998) “XANTHE TERRA
OUTFLOW CHANNEL GEOLOGY AT THE MARS PATHFINDER LANDING SITE” LPSC XXIX
1158.pdf.
“Summary. Geologic mapping of southern Chryse Planitia and the Xanthe
Terra outflow channels has revealed a sequence of fluvial events which
contributed sediment to the Mars Pathfinder landing site (MPLS). Three
major outflow episodes are recognized: (1) broad sheetwash across Xanthe
Terra during the Early Hesperian period, (2) Early to Late Hesperian
channel formation of Shalbatana, Ravi, Simud, Tiu, and Ares Valles, and
(3) subsequent flooding which deepened the channels to their current
morphologies throughout the Late Hesperian. Materials from the most
recent flooding, from Simud and Tiu Valles, and (to a lesser extent)
materials from Ares Vallis, contributed the greatest amount of sediment
to MPLS.”
[24] <#_ftnref24> Ibid.
“Following sheetwash, Mawrth Vallis was formed, possibly resulting from
the discharge of floods from Margaritifer and Iani Chaos. A broad area
of subdued terrain east of Ares Vallis indicates buried and embayed
craters to the south of Mawrth Vallis. Floods could have passed over
this surface before excavating Mawrth, then drained downslope into
Acidalia Planitia. Alternatively, the subdued area could be a spill zone
formed during the early excavation of Ares Vallis. Channelization
continued in the Late Hesperian with the development of Shalbatana,
Ravi, Simud, Tiu, and Ares Valles. Shalbatana Vallis possibly formed by
subterranean discharge from Ganges Chasmata [7], and Ravi was excavated
by flooding from Aromatum Chaos. Simud and Tiu Valles then developed by
floods from Hydraotes and Hydaspis Chaos, and Ares Vallis developed by
flooding from Iani Chaos. Cross-cutting relationships in Ares and Tiu
Valles suggest that multiple floods occurred within these channels.”
[25] <#_ftnref25> P. D. Lanagan et al (2001) “GEOMORPHOLOGIC MAPPING OF
CERBERUS PLAINS, MARS” LPSC XXXII 2077.pdf
“Fluvial features in the Cerberus plains cut into and are covered by
lava flows [2]. MOC images, which show streamlined islands and
longitudinal grooves, and MOLA topography suggest that water that carved
the more recent of these channels originated from Cerberus Rupes or in
regions of ground collapse highland rem-nants north of Cerberus Rupes,
ran south into the Cer-berus plains, and finally emptied into Amazonis
Plani-tia via the Marte Valles outflow channels [1].”
[26] <#_ftnref26> Lanagan et al (2001) Rootless cones on Mars indicating
the presence of shallow equatorial ground ice in recent times”,
/Geophysical Research Letters,/ vol. 28, p. 2365-2368.
“*C*lusters of small cones on the lava plains of Mars have caught the
attention of planetary geologists for years for a simple and compelling
reason: ground ice. These cones look like volcanic rootless cones found
on Earth where hot lava flows over wet surfaces such as marshes, shallow
lakes or shallow aquifers. Steam explosions fragment the lava into small
pieces that fall into cone-shaped debris piles. Peter Lanagan, Alfred
McEwen, Laszlo Keszthelyi (University of Arizona), and Thorvaldur
Thordarson (University of Hawai`i) recently identified groups of cones
in the equatorial region of Mars using new high-resolution Mars Orbiter
Camera (MOC) images. They report that the Martian cones have the same
appearance, size, and geologic setting as rootless cones found in
Iceland. If the Martian and terrestrial cones formed in the same way,
then the Martian cones mark places where ground ice or groundwater
existed at the time the lavas surged across the surface, estimated to be
less than 10 million years ago, and where ground ice may still be today.”
[27] <#_ftnref27> (2003) Los Angeles National laboratory News and Public
Affairs, News Releases, Photos. Available online at:
http://www.lanl.gov/orgs/pa/News/cover_epi.jpg
[28] <#_ftnref28> M. Caplinger February (1994) “Determining the age
of surfaces on Mars” Malin Space Science Systems, Available online at:
http://www.msss.com/http/ps/age2.html
[29] <#_ftnref29> D. E. Smith and M. T. Zuber (2004) “Gravitational
effects of flooding and filling of impact basins on Mars” LPSC XXXV
1923.pdf.
“*Introduction. *The presence of large impact basins and the low
northern plains that might have contained ice or liquid water at an
earlier stage of Mars’ evolution suggests that the global gravity field
could have been different in the distant past than it is today. In
addition, any significant change in the distribution of mass affects the
moments of inertia and consequently and could conceivably change the
position of the Polar Cap and the length of day. Similar effects could
have been produced by large erosional processes, such as the removal of
crustal material from the Arabia Terra region and subsequent
re-depostion in the Chryse region of the northern plains [1]. We have
endeavored to estimate the magnitudes of material that might have been
involved in these processes and their possible effect on the gravity and
dynamics of Mars. We have used present-day topography [2] and gravity
field [3] as a starting point, recognizing that both the result of the
processes that we are trying to study rather than the state at the times
of interest.
*Basin Volumes. *The largest volume (arbitrarily defined below zero
elevation) that could have been filled with H2O in the past is the
northern plains (Fig. 1a) , which occupy about 47% of the surface of the
planet [2]. Because of its location, which is approximately symmetrical
about the Polar Cap, the additional mass associated with flooding
contributes largely to the zonal gravity field, particularly degrees 1,
2 and 3, with small changes to the moments of inertia. (Note: we do not
account for flexural effects.) Hellas (Fig. 1b) is the largest impact
basin, and if filled to the zero
elevation level would only hold about 10% of the volume of the northern
plains. But because of its location at 30 to 50S, 50 to 90oE, it has the
potential to have a larger effect on the moments. If suddenly filled
today it would want to move toward the equator and because it is almost
antipodal position to Tharsis it would move Tharsis southward [/cf. /4].
The second largest impact basin was probably Utopia [5, 6] but today it
is filled with sediments and volcanics [7], thus making the basin much
shallower than it was originally. It appears to have been a Hellas sized
basin and therefore might have been a significant contributor to
global-scale mass re-distribution. Argyre, in comparison to Hellas, has
only about 10% of the volume of Hellas as measured by today’s
topography, and has a relatively minor effect on the global mass
redistribution.”
[30] <#_ftnref30> A. T. Oner et al (2004) “The volume of possible
ancient ocean basins in the Northern Lowlands” LPSC XXXV 1319.pdf.
“*Discussion:* Our results for Arabia and Deu-teronilus shoreline
present-day topography are some- what lower than those obtained
previously [7,8]. the Meridiani shoreline our result is clearly lower than
that in [8], fundamentally due to the fact that these authors use an
excessively high value of 0 (with re-
spect to the global datum) for the mean paleoshoreline elevation,
whereas we use a mean elevation of ?1.5 km [17]. Elevational range and
geologic relations along Ara-bia shoreline, especially with respect to
the Tharsis region, suggests that this is not a true paleoshoreline
[7,8]. This implies that volumes obtained for the Ara-bia shoreline are
likely not representative of any an-cient martian *ocean*. Otherwise,
elevations in the puta-tive Meridiani shoreline are roughly similar to
those of the Arabia shoreline in northeast Arabia, Utopia (not taken
into account the Isidis basin), Elysium, and Amazonis regions. A
paleoshoreline through these Arabia shoreline portions and the Meridiani
shoreline would be a better candidate to represent a true *ancient*
oceanic limit [5,18]: areas, volumes, mean depths and GELs obtained here
for the Meridiani shoreline would be roughly valid for this *possible*
paleoshoreline.”
[31] <#_ftnref31> (2003) Los Angeles National laboratory News and Public
Affairs, News Releases, Photos. Available online at:
http://www.lanl.gov/orgs/pa/News/cover_epi.jpg
Also JPL 2002 image releases, Global Map of Epithermal Neutrons, May 28
2002, PIA 3800. Available online at:
http://www.jpl.nasa.gov/images/mars/pia3800_caption.html
[32] <#_ftnref32> Greg M. Orme and Peter K. Ness (2003) “Martian
Spiders” New Frontiers in Science, Fall 2003. /Viking Spiders.
/Available online at:
http://newfrontiersinscience.com/Members/v02n03/a/NFS0203a.shtml
“Oddly enough, Viking 2 [137]
landed [138]
nearly in the middle of a sub polar area that seems truly spider
like [139]
.
Interestingly, some troughs were found near Viking 2 [140]
.
While other explanations have been suggested, the presence of the
spiders nearby and their association with sometimes polygonal
ravines makes these troughs possibly spider ravines. These
"enigmatic troughs" [141]
can be traced in a sequence of photos [142]
.
If they are spider ravines, it might indicate that when the spiders
seasonally dissipate, they might leave ravines that are too shallow
to see. There are also pits [143]
in the area of unknown origin. In /The Martian Landscape /, Figures
195 [144]
,199[145]
,
and 200 [146]
may also be troughs. Figures 290, 210 and 211 [147]
show paler areas devoid of rocks, which may be related to spiders.
Of course, there are many other explanations but the proximity to
the spiders makes these interesting. In imagery of the landing site
[148]
,
spider branches are 1-3 pixels wide where a pixel's width [149]
is 9.46 meters [150]
.
Since spiders typically have a paler albedo and a comparable branch
width to these pale patches, it is possible that they might be
spider remnants.”
[33] <#_ftnref33>Peter K. Ness
and Greg M. Orme
, (2002). “Spider-Ravine
Models and Plant-like Features on Mars - Possible Geophysical and
Biogeophysical Modes of Origin” /Journal of the British Interplanetary
Society//, 8/ February 2002. Vol 55 No 3/4, March-April Edition, Pp
85-108. available online
at http://www.martianspiders.com
[34] <#_ftnref34> D. E. Shean and J. W. Head (2003) “Pavonis Mons
fan-shaped deposit- a cold based glacial model” 6^th International
Conference on Mars 3036.pdf
“Introduction: Each of the three Tharsis Montes volcanoes on Mars has
unusual fan-shaped deposits
located exclusively to the west-northwest of each shield. The fan-shaped
deposits of the Tharsis Montes
generally share three major facies: 1) a ridged facies, 2) a knobby
facies, and 3) a smooth facies. Any ex-
planation for the origin of the fan-shaped deposits must take into
account both the similarities and differences in their morphologies,
their approximately similar Amazonian age, and the fact that all three
occur on the west-northwestern sides of the volcanoes [1]. Based on
Viking Orbiter data, several models have been pro- posed for their
formation, including massive landslides [2], glacial processes [3,4,5,6]
and pyroclastic flows [6]. We support a glacial origin for the
fan-shaped deposits and refine the previous models using new data from
both the Earth and Mars. Based on Viking Or-biter data, Williams [3] and
Lucchitta [4] suggested that the fan-shaped deposits were the result of
the deposition of moraines due to recession of local ice caps that
formed on the volcanoes from mixtures of emanated volatiles and erupted
ash [4]. Scott et al. [6] suggest an explanation combining glacial and
volcanic processes
…
We interpret these ridges as drop moraines formed at the margins of a
retreating cold-based glacier [7].
The fact that these ridges can be seen in the proximal regions of the
Pavonis fan-shaped deposit suggests that at least one major phase of
retreat and deposition oc-curred. The ridges are superposed on
underlying to-pography, including a lobate lava flow to the west, and
are not deflected by obstacles. The fact that the ridged facies is
observed up to elevations of 9.2 km above Mars datum on the northern
flanks of Pavonis suggests that a large glacier would have covered a
significant portion of the flanks of the shield.”
[35] <#_ftnref35> E.R. Fuller and J.W. Head III (2002) “GEOLOGIC HISTORY
OF THE SMOOTHEST PLAINS ON MARS (AMAZONIS PLANITIA) AND ASTROBIOLOGICAL
IMPLICATIONS” LPSCXXXIII 1539.pdf
“The cryosphere, a frozen layer of ice and regolith, has been acting as
a global aquitard to the groundwater system below [e.g., 9]. Once the
cryosphere is breached, the water, under hydrostatic pressure, emerges
with very high flow rates, and continues flowing until pressure
equilibrium is reached. This water flowed through Marte Vallis, eroding
channels and debouching into Amazonis Planitia. This catastrophic
outflow was shortly followed by lava outflow; the magma flowed through
the fracture and released flood lavas onto the surface. This lava
followed the path of the water, re-surfacing Marte Vallis and pouring
into Amazonis
Planitia. As it flowed over the water-saturated surface, the
phreatomagmatic interactions created rootless cone structures [see also
discussion in 10]. *Astrobiological implications:* The lava flows
associated with the emplacement of these plains have been dated as
extremely young geologically (less than 10 million years old [11]). If
fossil or extant life existed at depth in the subsurface groundwater
system at this time (a troglodytic fauna), it is highly likely that they
would be among the material erupted to the surface, and washed down into
Elysium Planitia and Amazonis Planitia. The fate of such effluents under
current martian conditions has recently been modeled [12] and it has
been shown that standing bodies of water at this scale would quickly
freeze over and sublimate, leaving a sedimentary sublimation residue.
Thus, Elysium and Amazonis Planitiae would be excellent locations to
sample recently emplaced freeze- dried troglodytic faunal remains.”
[36] <#_ftnref36> JPL Planetary Photojournal PIA04253 “Map of Martian
Iron at mid-latitudes”. Available online at:
http://photojournal.jpl.nasa.gov/catalog/PIA04253
[37] <#_ftnref37> O. Aharonson et al (1998) “Mars: Northern hemisphere
slopes and slope distributions” GEOPHYSICAL RESEARCH LETTERS, VOL. 25,
NO. 24, PAGES 4413-4416, DECEMBER 15, 1998.
“Characterization of Martian surface slopes from the aerobreaking hiatus
phase of the MGS mission provided several insights. Regional slopes
across prominent canyons measured on a 10-km baseline range from 0 ? 5_
for regions which have undergone mass wasting and collapse, up to
approximately 30_ for less modi_ed scarps. The average slopes across the
dichotomy boundary are small, < 1_, but on a local
scale can execed 20_. The northern lowlands are found to be unusually
smooth and form a distinct statistical population. Other distinct
populations correspond to the rough highlands and the extremely smooth
Amazonis Planitia region. Amazonis is markedly smoother than any other
large scale surface observed onMars, than volcanic plains on both the
Moon and Venus, and than an example of desert terrain on the Earth. Its
statistical properties resemble most closely certain terrestrial
depositional environments including
oceanic abyssal plains and sedimentary basins. Given previously
hypothesized scenarios for Mars' geological past [Carr, 1981], the
evidence so far may be consistent with an origin for Amazonis in which
extensive aeolian deposition follows a volcanic resurfacing event. Also
possible is a modicational history in which water provides a sedimentary
environment capable of efficiently smoothing meter scale topography.”
[38] <#_ftnref38> E. R. Fuller and J. W. Head III (2002) “Amazonis
Planitia: The role of geologically recent volcanism and sedimentation in
the formation of the smoothest plains on Mars” JOURNAL OF GEOPHYSICAL
RESEARCH, VOL. 107, NO. E10, 5081, doi:10.1029/2002JE001842, 2002.
“[9] Parker et al. [1993] drew Contact 2, one of two interpreted
shorelines for their proposed Hesperian northern ocean, near the margins
of the central smooth unit of Amazonis Planitia. Head et al. [1999],
using MOLA data, assessed the elevation of the two contacts, and found
that Contact 1 deviated substantially from an equipotential line, but
that Contact 2 was much closer to being level, with a mean elevation of
3760 m below the Martian datum. Figure 5e shows the trace of the _3760 m
contour through the
Amazonis Planitia region.
…
[10] Morris and Tanaka [1994] mapped the eastern edge of Amazonis
Planitia in their analysis of the Olympus Mons region. They identified
two plains subunits of the Arcadia Formation (Figure 2): Aa1 and Aa2,
both volcanic plains mantled by aeolian deposits. They also present
evidence that the age of mapped volcanic units associated with Olympus
Mons span the Middle to Late Amazonian, and that if the
aureole deposits represent the collapse of a proto-Olympus Mons edifice,
then extrusive activity must have extended back to the Late Hesperian.
On the basis of their mapping, they favor a landsliding and
gravity-spreading mechanism [see also Tanaka, 1985; Francis and Wadge,
1983], but point out that this requires a lubricant such as water or
ice. They further point out a weakness of their hypothesis: ‘‘if a huge,
proto-Olympus Mons had formed (necessary for the landsliding and
gravity-spreading mechanisms), extant lava flow fields beyond the
aureoles might be expected, but they are absent’’ [Morris and Tanaka,
1994, p. 15].
…
Its smoothness is comparable only with Earth regions shaped by long-term
aqueous deposition, such as ocean floors and the North American Great
Plains (the former location of an epeiric sea) [Aharonson et al., 1998].
Re-examination of Pass 31 shows that the smoothest region within the
several thousand
kilometer-long track corresponds precisely with the central smooth unit
of Amazonis Planitia identified in this study (Figure 7).”
[39] <#_ftnref39> Such as :
http://planetarynames.wr.usgs.gov/images/mola_regional.pdf
[40] <#_ftnref40> M. A. de Pablo (2004) LPSC XXXV 1223.pdf.
“The subsequent evolution of Atlantis Basin is closely related to the
evolution of Eridania Lake. The
desiccation of Eridania Lake, probably during the Late Noachian [5],
might have predated the existence of a series of reduced and
interconnected lakes in the area, in which Atlantis might have been
included. In this
work we propose the name /Atlantis Lake /for the lake formed inside this
basin and originated in the decrease
of the water level of the Eridania Lake. Water probably flowed in the
area from the South, initially
draining to Southwest, but later forming an endorreic basin until its
complete desiccation. In relation with
this evolutionary sequence, the presence of ‘mesas’ in the basin edges
(Fig. 1-f) have been interpreted as
sedimentary materials deposited in the floor of the ancient Eridania
Lake, and subsequently eroded. This
interpretation, together with the presence of relatively recent collapse
areas (Fig. 1-g) and mud-flow deposits (Fig. 1-h) around the Atlantis
Chaos terrain, indicate the existence of liquid water in the recent
past. The appearance of linear structures in the interior of Atlantis
basin has been interpreted as indicative of possible ancient dike
systems [8], whose new activation would explain the existence of the
subsidence zones and the mud-flow deposits by the fusion of the
permafrost. Equally, the presence of
gullies (Fig. 1-i) in several closed basins near to Atlantis Basin (as
Gorgonum Chaos [9]), makes
feasible the existence of recent liquid water under the surface [10]
[11] [12] [13].
*Astrobiological interest: *The intense volcanic and tectonic
activities, and the presence of possible
dikes in the area, as well as the relation of Atlantis with the former
wide Eridania Lake, the gullies, and
the sedimentary deposits, all highlight the astrobiological interest of
Atlantis. A heat source
related to tectonovolcanic activity and flowing and ponded water are
both hypothesized to have been
present in the basin in different periods of the Martian history,
perhaps until recent times (Late Amazonian).”
[41] <#_ftnref41> Mars Exploration Rover Mission Press Releases (April
1, 2004). Available online at:
http://marsrovers.jpl.nasa.gov/newsroom/pressreleases/20040401a.html
“Gusev is halfway around the planet from the Meridiani region where
Spirit's twin, Opportunity, recently found evidence that water used to
flow across the surface.
"This is not water that sloshed around on the surface like what appears
to have happened at Meridiani. We're talking about small amounts of
water, perhaps underground," said Dr. Hap McSween, a rover science team
member from the University of Tennessee, Knoxville.
"The evidence is in the form of multiple coatings on the rock, as well
as fractures that are filled with alteration material and perhaps little
patches of alteration material," McSween said during a press conference
at NASA's Jet Propulsion Laboratory, Pasadena, Calif.”
[42] <#_ftnref42>Mars Exploration Rover Mission Press Releases (March 5,
2004). Available online at:
http://marsrovers.jpl.nasa.gov/newsroom/pressreleases/20040305a.html
“NASA's Spirit has found hints of a water history in a rock at Mars'
Gusev Crater, but it is a very different type of rock than those in
which NASA's Opportunity found clues to a wet past on the opposite side
of the planet.
A dark volcanic rock dubbed "Humphrey," about 60 centimeters (2 feet)
tall, shows bright material in interior crevices and cracks that looks
like minerals crystallized out of water, Dr. Ray Arvidson of Washington
University, St. Louis, reported at a NASA news briefing today at NASA's
Jet Propulsion Laboratory, Pasadena, Calif. He is the deputy principal
investigator for the rovers' science instruments.
"If we found this rock on Earth, we would say it is a volcanic rock that
had a little fluid moving through it," Arvidson said. If this
interpretation is correct, the fluid -- water with minerals dissolved in
it -- may have been carried in the original magma that formed the rock
or may have interacted with the rock later, he said.”
[43] <#_ftnref43> R. P. Irwin III and T. A. Maxwell (2004) LPSC XXXV
1852.pdf.
“*Introduction: *At 900 km long, 8?15 km wide and up to 2,100 m deep,
Ma’adim Vallis is one of the largest valleys in the Martian highlands.
The valley descends northward and terminates at the landing site for the
Spirit Mars Exploration Rover at Gusev Crater, which acted as a
detention pond or terminal basin for Ma’adim flows [1]. Previously we
identified the valley head at the breached drainage divide of an
enclosed basin in the mid-latitude highlands. Along with characteristics
of the head basin, this feature suggested that the valley was carved
primarily during a single paleolake overflow at the Noachian/Hesperian
boundary [2] (~3.7 Ga [3]). Earlier work had suggested that Ma’adim
Vallis was carved over a prolonged period up to 1.8 Ga by episodic
groundwater-fed flows [4?10]. Here we investigate the valley’s longevity
using crater counting, topography, and flow hydraulics. These
analyses provide quantitative support for development of the valley
during a brief overflow, followed by a
geologically brief period of tributary development.”
[44] <#_ftnref44> K. L. Thomas-Keptra et al (2004) “Determination if the
three-dimensional morphology of ALH84001 and biogenic MV-1 magnetite:
comparison of results from electron tomography and classical
transmission electron microscopy” LPSC XXXV 2030.pdf.
“*Introduction *Dated at ~3.9 billion years of age, carbonate disks [1],
found within fractures of the host rock of Martian meteorite ALH84001,
have been interpreted as secondary minerals that formed at low
temperature [e.g., 2] in an aqueous medium [e.g., 3]. Heterogeneously
distributed within these disks are magnetite nanocrystals that are of
Martian origin. Approximately one quarter of these magnetites have
morphological and chemical similarities to magnetite particles produced
by magnetotactic bacteria strain MV-1 [4], which are ubiquitous in
aquatic habitats on Earth. Moreover, these types of magnetite particles
are not known or expected to be produced by abiotic means either through
geological processes or synthetically in the laboratory. The remaining
three-quarters of the ALH84001 magnetites are likely products of
multiple processes including, but not limited to, precipitation from a
hydrothermal fluid, thermal decomposition of the carbonate matrix in
which they are embedded, and extracellular formation by dissimilatory
Fe-reducing bacteria. We have proposed that the origins of magnetites in
ALH84001 can be best explained as the products of multiple processes,
one of which is biological.
[45] <#_ftnref45> H. J. Leask et al (2004) “The formation of Aromatum
Chaos and the water discharge rate at Ravi Vallis” LPSC XXXV 1544.pdf.
“*Summary: *The Aromatum Chaos depression- Ravi Vallis outflow channel
system is sufficiently
simple that water flow rate and volume estimates can be made that throw
light on processes operating to
form the Aromatum and Ravi features. Typical discharge rates through
Ravi Vallis are estimated at 3
x 106 m3 s-1. By assuming a high sediment load in the water we find a
minimum duration of ~2 months.
Too much water flowed in the channel to be explained by cryosphere
melting alone, and drainage
of a local aquifer system delineated by intrusions is clearly implicated.
*Aromatum Chaos: *The main Aromatum Chaos depression is a truncated
triangle ~92 km long and an
average of 30 km wide (Fig. 1). Its interior consists mainly of a mass
of blocky-chaotic terrain, with
blocks generally becoming progressively smaller towards its Eastern end.
Some larger blocks at the
Western end show some evidence of rotational slumping and also appear to
be less eroded, having
flat tops showing a rather angular connection between the flat top and
the walls. The edges of
Aromatum Chaos show strong evidence of local structural control and so,
in an attempt to look for
similar control of the interior, we examined all MOLA profiles crossing
the interior, and found 30
profiles which collectively crossed the tops of 20 blocks. From these we
measured the absolute heights
(relative to Mars datum) of the tops of the blocks and their depths
below the rim of the depression. The
tops of blocks lie between 1,008 m and 2,361 m below the rim and show no
systematic correlation
with depth below rim or height above floor, suggesting piecemeal
collapse rather than a structural
control on their subsidence.”
[46] <#_ftnref46> N. Coleman (2004) LPSC XXXV1299.pdf.
“*Floodwater Sources: *Confined groundwater was the apparent source for
the initial outflows. If this were the only source the flow could not
have been sustained because confined aquifers, once released, tend to
depressurize rapidly. The unconfined dewatering of an aquifer takes much
longer. In addition, the presence of an ice-covered lake in ancestral
Ganges Chasma would
have provided a substantial reservoir to recharge the aquifer source for
both Ravi V. [7] and Shalbatana V. [7, 10], permitting outflows over an
extended period. If the flows were concurrent, then the flooding
occurred in mid- to upper-Hesperian because Shalbatana V. incised
ridged plains material of lower Hesperian age [11].”
[47] <#_ftnref47> C. Woodworth-Lynas and J. Guigne (2004) “Extent of
floating ice in an ancient Echus Chasma/Kasei Valles valley system,
Mars” LPSC XXXV 1571.pdf.
“*Introduction: *From images of the Echus Chasma/Kasei Valles valley
system we present further, new observations of surficial Martian
features that are interpreted to be the result of interactions between
the keels of flat-bottomed floating ice floes with a submerged sediment
[1,2]. These features are proxy indicators of three basic environmental
conditions: the former presence of a water body; the water body was
seasonally, or perhaps permanently, covered by ice floes; the water area
was large enough for winds, currents or both to drive the floes forward
during ice/lakebed interaction. We also present an analysis of
shorelines. These observations are made from analyses of Mars Global
Surveyor Mars Orbiter Camera (MOC) images. In places we have observed
several, closely-spaced, terraces
interpreted to be shorelines preserved at different elevations along the
margins of the valley system. We use the geographic distribution of the
floating ice-related features and shoreline terraces to define the
limits of floating ice in the valley system. We compare the shoreline
boundaries with equipotential (waterline) surfaces using Mars Orbital
Laser Altimeter (MOLA) data, and estimate the volume of water and
floating ice that occupied the valley system.”
[48] <#_ftnref48> T. Nakamura and E. Tajika (2002) “Evolution of the
climate system of Mars: effects of obliquity change” LPSC XXXII 1057.pdf.
“The obliquity change could cause a climate jump in the Martian climate
system on short timescale. Figure
2 shows the annual mean atmospheric pressure as a function of the
obliquity. The present solar constant
and 2.0 bar of the total amount of CO2 in the system are assumed for a
nominal example. There are two
branches of the solution. One is a “cold” residual-cap solution branch,
and the other is a “warm” no-ice-cap
solution branch. It is noted that the residual-cap solution branch
disappears in higher obliquity region. On
the other hand, the no-ice-cap solution branch does not exist in lower
obliquity region. Therefore, climate
jumps should occur at the ends of two branches. Assuming the state I in
Figure 2 as an initial state, for
example, when the obliquity increases, the state should change to be the
state II. If the obliquity continues to increase, a climate jump will
occur from the state II to III to reach the state IV. This climate jump
results in a drastic increase in the atmospheric CO2 pressure, thus
warming. On the other hand, starting from the state is IV, if the
obliquity decreases, the state changes from the state IV to I via a
climate jump from the state V to VI. In this case, the climate jump
results in a decrease in the atmospheric pressure, thus cooling. It is,
therefore, suggested that the Martian climate could have dramatically
changed repeatedly in short-term cycles during the Martian history.”
[49] <#_ftnref49> N. G. Barlow and J. M. Dohm (2004) “Impact craters in
Arabia Terra, Mars” LPSC XXXV 1122.pdf.
“*Discussion*: Crater morphologic and central pit data suggest that
Arabia hosts a subsurface volatile rich
reservoir of ice and possibly liquid water. The crater data are just one
indicator of the uniqueness of
Arabia Terra. The combined stratigraphic, topographic, structural,
crater, geomorphic, geophysical,
elemental, and thermophysical signatures suggest that Arabia is unusual
compared to other highlands regions [1]. GRS neutron spectrometer data
reveal Arabia to be one of the most H2O-rich areas in the equatorial
region of Mars [10, 11]. The correlation of this region with crater
indicators of subsurface volatiles suggest that volatiles exist over a
range of depths in this region, from less than a meter (GRS/NS analysis)
to over 2 km depth (based on crater depth-diameter analysis). The
existence of ejecta and central pit features over a range of crater
preservation ages indicates that this volatile reservoir has existed for
a substantial amount of Martian history, perhaps extending back into the
Noachian based on the ages of ejecta craters [12].”
[50] <#_ftnref50> J. M. Dohm et al (2004) “Ancient giant basin/aquifer
system in the Arabia Region, Mars”. LPSC XXXV 1209.pdf.
“Magnetic anomalies are observed in this region, although the magnitude
is diminished relative to the anomalies in the Terra Cimmeria region
[1,2]. The impact would have erased any preexisting magnetic anomalies
in the crust as is seen with Hellas and Argyre. If, however, the impact
occurred when the dynamo was active, the crust would have a chance to
reacquire magnetization. The diminished intensity could indicate that
the dynamo was active but in a waning stage. On the other hand, the
reduction in magnetic signals may be the result of deep burial by basin
infill. Although there is no geophysical manifestation of a large buried
impact basin in the gravity or magnetic data (e.g., circular positive
mascons as noted for Argyre, but subdued for Hellas), the extreme age of
the event may preclude any detectable geophysical signature and may in
fact explain the uniform appearance of the gravity.”
[51] <#_ftnref51> J. Arkani-Hamed and D. Boutin (2003) “Polar wander of
Mars: Evidence from magnetic anomalies” Sixth International Conference
on Mars. 3051.pdf.
“*Introduction: *The polar wander of Mars has been suggested by many
investigators. The
quasi-circular surface morphology of the deposits in the polar region
detected by Mariner 9 mission led Murray and Malin [1973] to suggest
that the Martian rotation axis has wandered by 10-20 degrees in the last
~100 Myr. Melosh [1980] gradually removed the mass of Tharsis bulge
while diagonalizing the moment of inertia tensor of Mars, and showed
that the Martian rotation
axis has displaced by about 25 degrees due to the formation of the
bulge. The similarity between
the deposits on Mesogaea, south of Olympus, and those in the polar
region led Schultz and Lutz
[1988] to suggest a polar path with a total of 120 degree wandering.
Long-term rotational dynamics of Mars was theoretically investigated by
Spada et al. [1996] through modeling Olympus mountain as a point mass,
initially located at 45 degree latitude on the surface, and allowing the
mass to reach the equator. They considered a comprehensive suit of
internal structure models of Mars with mantle viscosity ranging from
1021 to 1023 and imposed the Murray and Malin's constraint of 10-20
degree polar wander in the last 100 MYr. The authors concluded that the
mass will reach the equator within less than 2 Gyr., in a much shorter
time for low viscosity mantle models. It is also shown that a thick
elastic lithosphere atop a viscous mantle increases polar wander because
of elastically supporting the surface mass and allowing its greater
influence on the rotational dynamics of Mars [Willmann, 1984;
Stiefelhagen, 2002]. The Mars Global Surveyor magnetic data have
provided new evidence for the polar wander of Mars. Arkani-Hamed (2001a)
estimated the paleomagnetic Polar Cap positions of Mars through modeling
10 small and isolated magnetic anomalies. Seven out of the 10 Polar Caps
clustered within a radius of 30 degrees centered at 25N, 225E. Hood and
Zakharian (2001) modeled the source bodies of two magnetic anomalies
near the north Polar Cap. One of the anomalies was included in the 10
anomalies modeled by Arkani-Hamed, and the Polar Cap positions of this
anomaly determined by the authors were very close. Assuming that the
diPolar Cap core field axis coincided with the rotation axis, the
clustering of the Polar Caps suggests that the rotation axis has
wandered by about 65 degrees since the magnetic source bodies were
magnetized. This critical assumption that links the diPolar Cap core
field axis to the rotation axis presently holds for both terrestrial
planets with active core dynamo, Earth and Mercury, and possibly for
Earth throughout its history. We make the same assumption in this paper.”
[52] <#_ftnref52> I.G. Mitrofanov et al (2004) “Arabia and Memonia
equatorial regions with high content of water: data from HEND/ODYSSEY”
LPSC XXXV (2004) 1640.pdf.
“*Results. *The consistency of HM and DLM with observational data was
tested for the samples of pixels for
Arabia and Memnonia. It was shown that DLM model is better supported by
the observational data for Arabia and Memnonia in comparison with HM.
The best fitting values of parameters ?down were used for estimation of
water content at these regions. It was shown (see [7]) that North Arabia
(0?-45?E, 0?-30?S) contains on average 9.0 wt% of water under a dry
layer with thickness of 26 g/cm2; the South Arabia (0?-45?E, 0?-20?S)
contains on average 10.0 wt% of water under a dry layer with thickness
of 32 g/cm2; the Memnonia (180?-200?E, 0?-25?S) contains on average 9.0
wt% of water under a dry layer with thickness of 29 g/cm2. One
particular surface element with coordinates (30?E, 10?N) has the
smallest emission of epithermal neutrons in the equatorial belt (Figure
2).The best fitting subsurface parameters for this element correspond to
16 wt% water under a dry layer with thickness 29 g/cm2 [7]. This
estimate for the dry layer is consistent with the average value found
for the entire North Arabia. Therefore, this result showing a high
content of water at this surface element is not produced by
uncertainties in the model-dependent data deconvolution. The value of 16
wt% corresponds to a real minimum in epithermal neutron flux in Arabia.
We name this spot “Arabian Water-Rich Spot”, or AWRS. It lies around an
old eroded crater between craters Cassini and Schiaparelli.”
[53] <#_ftnref53> J.B. Dalton et al (2004) “Search for evaporate
minerals in Flaugergues Basin, Mars” LPSC XXXV 1869.pdf.
“the Flaugergues drainage divide in the Noachis region of Mars (16.8 S,
340.8 W; [4]) indicates areas
of water accumulation (Fig. 1). Putative paleolakes residing in craters
(e.g., Gusev Crater, Schiaparelli)
have already been examined for evidence of aqueous minerals. However,
basin flow models suggest that
craters deeper than low-lying basins do not necessarily drain large
areas. Raised crater rims often
isolate craters from their surroundings. The model has identified areas
of water accumulation fed by
large geographic areas which could produce enhanced transport of aqueous
materials. /MOLA /A shaded-relief map constructed from MOLA data was
used to assess the geomorphology of putative paleolake basins. Many were
found to exhibit smooth features suggestive of a lake bottom.”
[54] <#_ftnref54> Mars Exploration Rover Mission Press Releases (March
2, 2004). Available online at:
http://marsrovers.jpl.nasa.gov/newsroom/pressreleases/20040302a.html
“Scientists have concluded the part of Mars that NASA's Opportunity
rover is exploring was soaking wet in the past.
Evidence the rover found in a rock outcrop led scientists to the
conclusion. Clues from the rocks' composition, such as the presence of
sulfates, and the rocks' physical appearance, such as niches where
crystals grew, helped make the case for a watery history.
"Liquid water once flowed through these rocks. It changed their texture,
and it changed their chemistry," said Dr. Steve Squyres of Cornell
University, Ithaca, N.Y., principal investigator for the science
instruments on Opportunity and its twin, Spirit. "We've been able to
read the tell-tale clues the water left behind, giving us confidence in
that conclusion."
Dr. James Garvin, lead scientist for Mars and lunar exploration at NASA
Headquarters, Washington, said, "NASA launched the Mars Exploration
Rover mission specifically to check whether at least one part of Mars
ever had a persistently wet environment that could possibly have been
hospitable to life. Today we have strong evidence for an exciting
answer: Yes."
[55] <#_ftnref55> These and many other shapes were independently found
by many researchers, we would like to acknowledge Michael Davidson and
Francisco J. Oyarzun.
[56] <#_ftnref56> P.R. Christensen et al (2000) “THE DISTRIBUTION OF
CRYSTALLINE HEMATITE ON MARS FROM THE THERMAL EMISSION SPECTROMETER:
EVIDENCE FOR LIQUID WATER” Lunar and Planetary Science XXXI 1627.pdf.
“Crystalline hematite has been mapped over an area in Sinus Meridiani
approximately 500 km in longitude extending approximately 200 km in
latitude [3]. The extent of this deposit very closely matches the
geomorphic boundary of a smooth, layered, friable unit that is
interpreted to be sedimentary sedimentary in origin [3, 9]. This
material may be the uppermost surface in the region, indicating that it
might be a later-stage sedimentary unit, or alternatively a layered
portion of the heavily cratered plains units. A second accumulation of
hematite approximately 60 x 60 km in size is observed in Aram Chaos (2°
N, 21° W). This site is also associated with layered materials and a
water-rich environment.”
[57] <#_ftnref57> M. D. Lane et al (2001) “UPDATE ON STUDIES OF THE
MARTIAN HEMATITE-RICH AREAS” LPSC XXXII 1984.pdf.
“Figure 4. Crater count diagram and isochrons for the Terra Meridiani
hematite-rich area. Filled symbols show the population of "fossil
craters" lying near the saturation equilibrium limit (upper straight
line), indicating a very ancient surface. Open symbols show the fresh,
recent craters created since the modern surface formed, indicating that
the area has been exposed for as little as a few million years. Our
interpretation is that an ancient (paleolake bed?) was covered by
sediments and exhumed only a few million years ago.”
[58] <#_ftnref58> L.R. Gaddis et al (2003) “MINERAL MAPPING IN VALLES
MARINERIS, MARS: A NEW APPROACH TO SPECTRAL DEMIXING OF TES DATA” LPSC
XXXIV 1956.pdf.
“Mineral abundance maps (Fig. 5) show basaltic lithologies for much of
the VM interior, in the form of high- and low-Ca pyroxenes (up to 24%
total) and plagioclase minerals (up to 28%) in layered deposits in the
walls and interior, as well as in dark materials at the base of canyon
walls. Note that the presence of surface dust in parts of Ophir and east
Candor Chasmata appears to decrease the apparent abundance of minerals
in these areas. The distribution of gray hematite agrees well with
previous results [18], but we see only (~8%) a small enrichment of red
hematite in the possible hydrothermal site in west Candor [14] (Fig. 6).”
[59] <#_ftnref59> F. S. Anderson et al (2003) “MINERALOGY OF THE VALLES
MARINERIS FROM TES AND THEMIS” Sixth International Conference on Mars
(2003) 3280.pdf.
“Our observations of hematite in the VM are similar to those seen by
Christensen et al., [37].”
[60] <#_ftnref60> D. C. Catling and C. P. McKay (2000) “Aqueous Iron
Chemistry on Early Mars: Was it Influenced by Life?” Journal of
Conference Abstracts Volume 5(2), 291.
http://camb.demonhosting.co.uk/JConfAbs/5/291.pdf
“The Thermal Emission Spectrometer on NASA's Mars Global Surveyor has
detected deposits of crystalline hematite [1] in Sinus Meridiani, Aram
Chaos and Vallis Marineris. These appear to be similar to terrestrial
iron formations that formed in the Earth's Pre-cambrian oceans. The
Sinus Meridiani deposit
exceeds ~105km2 in size, and consists of coarse-grained, grey, schistose
hematite [2]. Its age is ~4Ga or older based on counts of exhumed fossil
craters [3]. Terrestrial Banded Iron Formations (BIFs) are laminated
sediments deposited directly from solution. Pathological cases of
crystalline hematite are
particularly characteristic of the Late Proterozoic. These are
associated with glaciomarine deposits and possibly formed when oceanic
ice cover retreated. Iron oxides were precipitated when ferrous iron
reacted with dissolved O2. There is no question that the oxygen in the
late Proterozoic atmosphere originated
from photosynthetic organisms. Could iron formations that formed ~4 Ga
ago on Mars also be related to oxygenic photosynthesis?
…
On early Mars several mechanisms could precipitate iron oxides from
solution. However, these processes all stoichiometrically require
oxygen. There are only two possibilities for an oxygen source: (1) Small
quantities of oxygen were slowly produced as hydrogen escaped to space
and ferrous iron acted as a sink for this oxygen over an extended timescale.
(2) Early Mars had an oxygenic photosynthetic biosphere. Simple
calculations suggest that atmospheric oxygen was very scarce on a
volcanically active early Mars. The exposed deposits of hematite, if
they are deep, would require significant quantities of oxygen. Finally,
although many of the findings
suggestive of life in the ALH84001 meteorite have been disputed, the
strongest piece of evidence has always been magnetite crystals of
biogenic shape. It is interesting to note that magneto-tactic bacteria
use magnetite for a specific purpose: to move along a redox gradient
away from a surface environment dominated by oxygen.”
[61] <#_ftnref61> C.S Cockell (2003) “LIFE IN MARTIAN SNOWS –
MEASUREMENTS OF UV PROTECTION UNDER NATURAL ANTARCTIC SNOWS IN THE UVC
(254 nm)” Third Mars Polar Science Conference 6125.pdf.
“Convolved with a simple Mars radiative transfer model, the data
suggests that under ~6 cm of Martian
snow, DNA-damage would be reduced by an order of magnitude [2]. Under
approximately 30 cm of snow,
DNA damage would be no worse than that experienced at the surface of the
Earth. Although we do not
know the exact characteristics of Martian snows, these first-order data
suggest that burial in even modest coverings of Martian snows could
allow for the long-term survival (and if water if present, even growth)
of contaminant microorganisms at the Martian polar caps even under the
extreme UV fluxes of clear Martian
skies. These coverings of snow will also allow for enhanced preservation
of organics against UVdegradation. Intriguingly, at the depth at which
DNA damage is reduced to similar levels as those found on the surface of
present-day Earth, light levels in the photosynthetically active region
(400 to 700 nm) are still two orders of magnitude higher than the
minimum required for photosynthesis, showing that within snow-pack on
planets lacking an ozone shield, including Mars, UV damage can be
mitigated, but light levels are still high enough for organisms that
have a requirement for exposure to light for their energy needs.
Photosynthetic life is not expected at the Martian poles, but the data
reveal the apparently favourable radiation environment for life within
the polar caps.”
[62] <#_ftnref62> B. M. Hynek and R. J. Phillips (2001) “Evidence for
extensive denudation of the Martian highlands” Geology, 29, 407-410.
“Using high-resolution topographic data from the Mars Orbiter laser
altimeter (MOLA) instrument on the Mars Global Surveyor mission (Smith
et al., 1999), we have gathered evidence for a major fluvial
resurfacing event in the Martian highlands. We completed detailed
geomorphic mapping for the Margaritifer Sinus region (08–308S, 08–308W),
where resurfacing appears most evident. In addition, evidence from
adjacent areas suggests that this was not a localized event, but one
that affected at least 1 3 107 km2 (an area equivalent to the European
continent) of the cratered uplands. The topographic information allows
for the first time a separation of younger, low-standing fluvially
reworked terrains from older, high-standing erosional remnants. The
newly acquired MOLA data also allow the volume of eroded material to be
sensibly determined and minimum erosion rates to be estimated. The
erosional episode was limited in time to no more than several hundred
million years, and occurred ca. 4 Ga. The scale of the processes
involved strongly suggests, but does not demonstrate uniquely, that
precipitation must have played a major role in landscape denudation in
this region of Mars.”
[63] <#_ftnref63>Mars Exploration Rover Mission Press Releases (April
15, 2004). Available online at:
http://marsrovers.jpl.nasa.gov/newsroom/pressreleases/20040415a.html
“NASA's Opportunity rover has examined an odd volcanic rock on the
plains of Mars' Meridiani Planum region with a composition unlike
anything seen on Mars before, but scientists have found similarities to
meteorites that fell to Earth.
"We think we have a rock similar to something found on Earth," said Dr.
Benton Clark of Lockheed Martin Space Systems, Denver, science-team
member for the Opportunity and Spirit rovers on Mars. The similarity
seen in data from Opportunity's alpha particle X-ray spectrometer "gives
us a way of understanding 'Bounce Rock' better," he said. Bounce Rock is
the name given to the odd, football-sized rock because Opportunity
struck it while bouncing to a stop inside protective airbags on landing
day.
The resemblance helps resolve a paradox about the meteorites, too.
Bubbles of gas trapped in them match the recipe of martian atmosphere so
closely that scientists have been confident for years that these rocks
originated from Mars. But examination of rocks on Mars with orbiters and
surface missions had never found anything like them, until now.
"There is a striking similarity in spectra," said Christian Schroeder, a
rover science-team collaborator from the University of Mainz, Germany,
which supplied both Mars rovers' Moessbauer spectrometer instruments for
identifying iron-bearing minerals.”
[64] <#_ftnref64> WILLIAM I. AUSICH, et al. /J. Paleont., /76(6), 2002,
pp. 975–992 Copyright q 2002, The Paleontological Society
“0022-3360/02/0076-975 “ORDOVICIAN [DOBROTIVIAN (LLANDEILLIAN STAGE) TO
ASHGILL] CRINOIDS (PHYLUM ECHINODERMATA) FROM THE MONTES DE TOLEDO AND
SIERRA MORENA, SPAIN WITH IMPLICATIONS FOR PALEOGEOGRAPHY OF PERI-GONDWANA”
[65] <#_ftnref65> R. B. ARONSON, AND D. B. BLAKE (2001) “Global Climate
Change and the Origin of Modern Benthic Communities in Antarctica” AMER.
ZOOL., 41:27–39, Figures 1 and 3b.
[66] <#_ftnref66>U. RADWA¡SKA & A. RADWA¡SKI (2003) “The Jurassic
crinoid genus /Cyclocrinus /D’ORBIGNY, 1850: still an enigma” /Acta
Geologica Polonica, /Vol. 53 (2003), No. 4, pp. 301-320 Figures 3, 8, 9,
10, 11, 12, 13, and 14.
http://www.geo.uw.edu.pl/agp/table/pdf/53-4/radwanscy.pdf
[67] <#_ftnref67> JPL (2004) Mars Exploration Rover Mission raw images.
m/030/1M130846496EFF0454P2933M2M1
[68] <#_ftnref68>JPL (2004) Mars Exploration Rover Mission raw images.
m/034/1M131201699EFF0500P2933M2M1
[69] <#_ftnref69> R. T. SCHELBLE et al (2001) “HEMATITE MINERALIZED
BACTERIAL REMNANTS: IMPLICATIONS FOR MARTIAN HEMATITE DEPOSITS” LPSC
XXXII 1438.pdf.
“by Fe-oxides for extended periods of time. Although
banded iron formations have not so far been recognized
on Mars, hematite deposits have been observed.
Christensen, et al. [7] cite five possibilities for the origin
of the hematite deposits:
· Direct precipitation from standing, oxygenated
iron-rich water
· Precipitation from iron-rich hydrothermal fluid
· Low-temperature dissolution and precipitation
through mobile groundwater leaching
· Surface weatherings and coatings
· Thermal oxidation of magnetite-rich lavas
If bacteria did exist on Mars, their preservation by
Fe-oxides in any of these potential settings is possible.
Thus, the Martian hematite deposits would be an
excellent site to look for past life on Mars.
[70] <#_ftnref70>JPL (2004) Mars Exploration Rover Mission raw images.
m/029/1M130761497EFF0454P2953M2M1.JPG
[71] <#_ftnref71> A. Krasnopolsky et al. “DETECTION OF METHANE IN THE
MARTIAN ATMOSPHERE: EVIDENCE FOR LIFE” V. European Geosciences Union 1st
General Assembly, Nice, France, 25 - 30 April 2004. Available online
at: http://www.cosis.net/abstracts/EGU04/06169/EGU04-A-06169.pdf
Using the Fourier Transform Spectrometer at the Canada-France-Hawaii
Telescope, we observed a spectrum of Mars at the P-branch of the
strongest CH4 band at 3.3 µm with resolving power of 220,000. Summing up
the spectral intervals at the expected positions of 18 strongest
Doppler-shifted martian lines, we detected the absorption by martian
methane at a 3.9 sigma level. The observed CH4 mixing ratio is 11 ± 4
ppb. Total photochemical loss of CH4 in the martian atmosphere is equal
to 1.8×105 cm?2 s?1, and the CH4 lifetime is 440 years. Heterogeneous
loss of atmospheric methane is probably negligible, while the sink of
CH4 during its diffusion through the regolith may be significant. There
are no processes of CH4 formation in the atmosphere, so the
photochemical loss must therefore be balanced by abiogenic and biogenic
sources. The mantle outgassing of CH4 is 4000 cm?2 s?1 on the Earth and
smaller by an order
of magnitude on Mars. The calculated production of CH4 by cometary
impacts is 2.3 per cent of the methane loss. Methane cannot originate
from an extinct biosphere, as in the case of “natural gas” on Earth,
given the exceedingly low limits on organic matter set by the Viking
landers and the dry recent history which has been extremely hostile to
the macroscopic life needed to generate the gas. Therefore,
methanogenesis by living subterranean organisms is the most likely
explanation for this discovery. Our
estimates of the biomass and its production using the measured CH4
abundance show that the martian biota may be extremely scarce and Mars
may be generally sterile except for some oases.
[72] <#_ftnref72> Kerr (2004)* “*Methane Means Martians?”,*
*/ScienceNOW/ 2004: 1.
[73] <#_ftnref73> M. J. Mumma et al (2003)“[14.18] A Sensitive
Search for Methane on Mars.” DPS 35th Meeting, 1-6 September 2003
Session 14. Mars Atmosphere II Poster, Highlighted on, Wednesday,
September 3, 2003, 3:00-5:30pm, Sierra Ballroom I-II.
*“*CH_4 and its oxidation products (H_2 CO, CH_3 OH, C_2 H_6 ) on Mars
have received both observational (1) and theoretical attention (2, 3),
but have not been firmly detected. Owing to its short photochemical
lifetime (~ 300 years), the existence of significant methane would
indicate \underline{recent} release from sub-surface reservoirs; a
quantitative measure of the release rate could be inferred from its
present atmospheric abundance. Sub-surface methane could be primordial
(reduced cosmogonic carbon) (1) or biotic in origin (4); local
enhancements are expected if methane is released from discrete regions.
The presence of sub-surface hydrogen concentrations on Mars has been
inferred from local-enhancements in epithermal neutron fluxes measured
on Mars Odyssey (5), however, independent evidence is required to
establish its likely chemical form (e.g., water vs. hydrocarbons) in
low-latitude sites (Amazonia Planitia, and Schiaparelli-Cassini). We
suggest that enhanced methane there could test whether sub-surface
hydrogen is chemically bound in hydrocarbon moieties. In any case, a
quantitative measure of methane production would provide a key for
assessing models of biogenic vs. primordial origins. “