mirrored file at http://SaturnianCosmology.Org/ For complete access to all the files of this collection see http://SaturnianCosmology.org/search.php ========================================================== ================== (1) DID BLAND RUSH TO CONCLUSIONS? CONTROVERSY BREWING OVER RIO CUARTO CRATERS >From Sky & Telescope, 14 May 2002 http://skyandtelescope.com/news/current/article_602_1.asp By J. Kelly Beatty May 14, 2002 | A controversy is brewing over the origin of several unusual depressions in the Pampean plain of northern Argentina. For the last decade planetary scientists have considered a cluster of large, elongated pits near Rio Cuarto to be unique impact craters, gouged by a chunk of asteroid that glanced obliquely through the atmosphere and broke into pieces just before striking the Earth. The idea for such an impact swarm arose in 1991, when an expedition led by Peter Schultz (Brown University) and Argentine air-force pilot Ruben Lianza discovered samples of fused soil and even intact meteorites within the teardrop-shaped depressions. Subsequent laboratory work suggested that the Rio Cuarto event must have occurred within the past several thousand years. The impact hypothesis recently received its most serious challenge from a team led by Phil A. Bland (Open University, London). In the May 10th issue of Science, they detail a pair of meteorites found within the putative craters that not only have different makeups but also appear to have arrived on Earth 36,000 and 52,000 years ago - far longer than the age of the depressions in which they were found. Bland's team also contends that the strange depressions, up to 4½ kilometers long and 1 km wide, look much like hundreds of other smaller features scattered throughout the region - a situation far too unlikely to be caused by a single collisional event. This would suggest that the Rio Cuarto craters are not craters at all but rather long hollows carved and shaped over thousands of years by prevailing winds. In the process, the gradual removal of material exhumed meteorites that had fallen to Earth long ago. "I'd love them to be low-angle impacts," Bland told Sky & Telescope, "but I just don't think the evidence is there." But what of the fused-glass nuggets found by Schultz and Lianza? Bland says more of these have turned up at a site 400 km farther south, which suggests to him that they all came from a much bigger impact about 480,000 years ago. Such a catastrophic event would have splashed glassy droplets (known as tektites) over a very wide area and left behind a crater roughly 5 km across, which presumably lies hidden beneath the Pampas or offshore in the Atlantic. As terrifying as the oblique impacts might have been, observes H. Jay Melosh in the same issue of Science, "[Bland's] view of a shower of hot glass over a region as large as Texas suggests a far more lethal event half a million years ago." Not everyone finds Bland's work convincing. "I don't believe it," says cratering expert Christian Koeberl (University of Vienna). Koeberl says the glassy melt found within the depressions is, isotopically, "practically identical" to the surrounding soil, and its age (as determined by two different methods) is only 4,000 years - a far cry from a half million. Moreover, Schultz says he's now found four meteorites in the Rio Cuarto craters, and they're all the same class of chondritic stone. Resolving the origin of these controversial features may take years of careful field work and laboaratory analyses. Schultz contends, for example, that the Rio Cuarto craters have charateristics unlike those of the region's wind-deflation structures. But Bland counters, "I don't know what criteria he's basing that on. We couldn't detect any differences." Copyright 2002, Sky & Telescope =================== (2) "IMPROBABILITY" OF OBLIQUE-ANGLE IMPACTS >From Duncan Steel Dear Benny, Regarding the report on the Rio Cuarto structures carried in CCNet today, I am a little puzzled as to why people think that oblique-angle impacts are "improbable." While they are not the majority of cases, they are not as unlikely as one might imagine. The distribution of impact angles for cosmic impacts varies as [sin theta cos theta], where theta is the elevation angle above the horizontal. This happens to be the angular distribution both before and after gravitational focussing (meteor watchers will be familiar with the concept of "zenith attraction", this being the same thing, with the zenith angle being [90 deg - theta]). This is also be the distribution of impact angles on the solid Earth (or oceans), provided that the atmosphere does not cause any significant deceleration of the impactor; this will be the case for impactors in the size range under consideration here. The most likely impact angle is therefore 45 degrees (forget all those pictures with asteroids descending vertically). An impact elevation angle of 7 degrees was mentioned in the discussion of the Rio Cuarto structures; an impact at precisely this angle occurs with about one-quarter the likelihood of the most-probable angle of 45 degrees (i.e. [sin theta cos theta] is 0.5 if theta=45 deg, and 0.121 if theta=7 deg). The item did state, though, that the impact angle would have been "less than 7 degrees." Integrating the distribution over all angles below 7 degrees and normalising against the complete range of impact angles (0 to 90 degrees) one finds a 1.5% probability of such an oblique impact angle (i.e. one in 67). That's a small value, but not wildly unlikely. Regards, Duncan Steel =============== (3) COSMIC IMPACTS IMPLICATED IN BOTH THE RISE AND FALL OF DINOSAURS >From Andrew Yee Media Relations Rutgers Contact: Bill Haduch, 732/932-7084, extension 633 E-mail: bhaduch at ur.rutgers.edu May 16, 2002 Cosmic impacts implicated in both the rise and fall of dinosaurs NEW BRUNSWICK/PISCATAWAY, N.J. -- New abilities to detect layers of "space dust" in the earth's crust are building geological evidence that comets or asteroids colliding with earth not only helped wipe out the dinosaurs, but may have originally helped bring them to prominence about 200 million years ago. Dennis V. Kent, Rutgers geology professor, was among a team of geologists who analyzed footprints, bones and plant spores in more than 70 locations in eastern North America, as well as iridium dust and magnetic fields in four corresponding sediment layers in the Newark Basin. The team published its findings, "Ascent of Dinosaurs Linked to an Iridium Anomaly at the Triassic-Jurassic Boundary," in the May 17 edition of the journal Science. "Finding the element iridium, which is common in space objects, creates a time marker for comet or asteroid impacts." said Kent. "Correlating the finds with evidence of plant and animal life helps to tell us what happened." Using high-resolution spectrometry technology provided by Christian Koeberl of the University of Vienna in Austria, the scientists were able to make unprecedented comparisons of iridium levels in the parts-per-trillion range. Kent said another important find was a thin zone in the sediment, just below the Triassic-Jurassic boundary, where the magnetic field is reversed. This reverse zone can now serve as a marker to help identify the boundary location in the geological record. "Our research adds to the speculation that there was a comet or asteroid impact about 200 million years ago, followed relatively quickly by the rising dominance of dinosaur populations of the Jurassic period," said Kent. He suggested that the effects of the impact killed off or reduced many competitive species, clearing the way for dinosaurs to adapt and flourish. "Dinosaurs went on to dominate for the next 135 million years," he said, noting that their extinction is now commonly attributed to the ecological effects of yet another comet or asteroid impact -- this one about 65 million years ago. Besides his work at Rutgers, Kent is associated with the Lamont-Doherty Earth Observatory of Columbia University, as are his co-authors E.C. Rainforth and P.E. Olsen. Olsen's earlier research about Triassic-Jurassic transitions inspired the project. Other co-authors include Koeberl and H. Huber of the University of Vienna, H.-D. Sues of the Royal Ontario Museum, A. Montanari of the Osservatorio Geologio do Coldigiocom in Italy, S.J. Fowell of the University of Alaska-Fairbanks, and M.J. Szajna and B.W. Hartline, fossil collectors of Reading, Pa. EDITOR'S NOTE: Professor Kent may be contacted by phone at (732) 445-2044 or by e-mail at dvk at rci.rutgers.edu . ============= (4) ASCENT OF DINOSAURS LINKED TO AN IRIDIUM ANOMALY AT THE TRIASSIC-JURASSIC BOUNDARY >From Science, 17 May 2002 http://www.sciencemag.org/cgi/content/abstract/296/5571/1305 (login required) P. E. Olsen, D. V. Kent, H.-D. Sues, C. Koeberl, H. Huber, A. Montanari, E. C. Rainforth, S. J. Fowell, M. J. Szajna, B. W. Hartline Analysis of tetrapod footprints and skeletal material from more than 70 localities in eastern North America shows that large theropod dinosaurs appeared less than 10,000 years after the Triassic-Jurassic boundary and less than 30,000 years after the last Triassic taxa, synchronous with a terrestrial mass extinction. This extraordinary turnover is associated with an iridium anomaly (up to 285 parts per trillion, with an average maximum of 141 parts per trillion) and a fern spore spike, suggesting that a bolide impact was the cause. Eastern North American dinosaurian diversity reached a stable maximum less than 100,000 years after the boundary, marking the establishment of dinosaur-dominated communities that prevailed for the next 135 million years. Volume 296, Number 5571, Issue of 17 May 2002, pp. 1305-1307. Copyright © 2002 by The American Association for the Advancement of Science. All rights reserved. ================ (5) ASTEROID IMPACT TIED TO RISE OF DINOSAURS >From Space.com, 16 May 2002 http://www.space.com/scienceastronomy/planetearth/jersey_dinosaurs_020 516-1.html By Robert Roy Britt Senior Science Writer The history of dinosaurs and asteroids became further entwined today with the announcement that an impact from a space rock 200 million years ago may have eliminated some competition and helped the giant reptiles flourish and eventually dominate the planet. Scientists have long suspected that an asteroid led to the demise of dinosaurs' 65 million years ago. Research last year suggested that an earlier impact 251 million years ago might have allowed dinosaurs to evolve in the first place. Now a new study of more than 70 sites in North America finds evidence that the well-documented mass extinction 200 million years ago was also caused when an asteroid or possibly a comet hit Earth. Within 100,000 years of the event -- an evolutionary eyeblink -- dinosaurs radiated and multiplied swiftly, reaching their historical maximum diversity in the region. They went on to dominate the planet for 135 million years. The findings are based on footprints, bones, fern spores, and the discovery of elevated levels of iridium -- a rare element on Earth but one common among space objects. The results help build a sometimes controversial case that in the grand scheme of terrestrial time, space rocks frequently snuff out entire species while simultaneously breathing fresh life into the evolutionary process. The results, which need to be validated by further research, will be published in the May 17 issue of the journal Science. Rocky times Researchers have thought for more than a decade, and with growing certainty, that an impact played a critical role in the ultimate death of dinosaurs. Other species perished, too, in an event that allowed mammals to prosper in a world where there were fewer large creatures to step on them or swallow them whole. However only in recent years has evidence turned up linking earlier mass extinctions to impacts. The new research documents a widespread die-off that occurred at the boundary of the Triassic and Jurassic periods in time, when dinosaurs had begun to gain a foothold in what is now North America. The study found iridium in layers of rock in Earth's crust at several sites that have been traced back to the same point in time. The element is prevalent in asteroids and comets and can be left behind as a global signature when an incoming object vaporizes on impact and kicks up a dust storm that circles the planet. Though there is no evidence of a crater, the iridium "creates a time marker for comet or asteroid impacts," said Dennis V. Kent, a Rutgers University geologist and part of the research team. "Correlating the finds with evidence of plant and animal life helps to tell us what happened." Paul E. Olsen of the Lamont-Doherty Earth Observatory of Columbia University led the study. Asteroid or volcanism? An asteroid could certainly do the trick, experts say, creating years of winter-like conditions caused by tons of dust that blots out the Sun. Yet, other researchers have speculated that the extinction 200 million years ago was instead a result of increased volcanic activity, which would have pumped choking chemicals into the atmosphere. Some experts say a combination of an impact and increased volcanism might provide a one-two punch necessary to cause extinctions of many species. Either way, the case is not firm. "Considerably more geochemistry is needed to rule out a volcanic origin," Olsen told SPACE.com. "And much more sampling over a broader temporal and geographic range is needed to confirm that what we found is really a global event tied to an impact." Olsen said, however, that the team found iridium at levels two and three times higher than normal "background" levels found in sedimentary rock. This anomaly, or difference in levels, is not as high as has been documented for the so-called K-T impact that occurred 65 million years ago (and for which a crater exists). "The magnitude of our anomaly is small compared with that at the K-T boundary, but it is similar to anomalies at other known impacts," Olsen said. The iridium spike was found to be coincident with a spike in fern spores, thought to be a signal of recovery from an impact. Paul Sereno, the noted dinosaur hunter from the University of Chicago, said the study provides "critical new data on the origins and early evolution of dinosaurs that support a sharp break in the fossil record between the early and rarer dinosaurs of the Triassic period, and the larger dominant dinosaurs of the early Jurassic." The number and extent of the Triassic-Jurassic extinctions have been much debated. "Which is why this well-dated, well-supported find of iridium and a fern pollen spike in association with footprints is such key new information," Sereno told SPACE.com. "Doubtless it will spark new research into the question of how and when dinosaurs rose to dominance on land -- a question that may ultimately become as resolved as the events at the end to the dinosaur era." Other possible impacts A study last June, also reported in Science, found extraterrestrial gases trapped inside special molecules, known as fullerenes, in rock layers corresponding to an earlier and greater mass extinction, which occurred 251 million years ago. This event wiped out 75 percent of all species and was likely a first step in allowing dinosaurs to enter the scene. One of the researchers involved with that study, Robert Poreda of the University of Rochester, said the newer results need to be interpreted with caution. "Iridium can be an important tracer for studying impacts, but in some ways the overwhelming signal observed at the K-T site has caused some to view it as a sort of 'key' signal," Poreda said. "At two to three times the background signal [as in Olsen's study] the case can be made for a non-impact scenario." The elevated iridium, Poreda said, might reflect changes in sedimentation or accumulation rates where no impact occurred. He said several indicators need to coincide, from iridium results to fullerenes, shocked quartz structures and more. Nevertheless, Poreda said the new research "represents one of the first steps" in showing that the Triassic-Jurassic extinction was caused by a space rock. His own feeling, he said, is that a few years of study will show that to be the case. How it was done The new iridium study used a special technique called iridium coincidence spectrometry, which finds the element based on the ejection of two gamma-ray particles per atom after they have been irradiated in a nuclear reactor, to make fine comparisons of iridium in the sediment layer compared to older and newer layers. Christian Koeberl of the University of Vienna performed the work. Earlier attempts to find an iridium "spike" in the Triassic-Jurassic boundary did not succeed because the spectrometry equipment was not sensitive enough, the researchers said. The work is painstaking. Earth was an entirely different place 200 million years ago, with all the continents crowded into a single land mass called Pangea. Researchers must first locate exposed sedimentary layers, which may have been folded under and back out to the surface over the eons, and then properly date and sample them. Much of the evidence was collected in what are now parts of New Jersey and Pennsylvania, along with other archeological sites dotting the eastern United States. Copyright 2002, Space.com =============== (6) ASTEROID LET DINOSAURS RULE >From Andrew Yee [ http://www.nature.com/nsu/020513/020513-11.html ] Friday, 17 May 2002 Asteroid let dinosaurs rule Impact may have caused mass extinction that let hardy giants thrive By HELEN PEARSON A huge asteroid smashing into Earth may have let dinosaurs take over the Earth 135 million years before another one wiped them out, a controversial new study suggests. Dinosaurs flourished in the wake of a mass extinction 200 million years ago. But no one is sure what made so many plants and animals disappear. "The simplest scenario is that a very large asteroid struck our planet," says Paul Olsen of Columbia University in New York. Olsen's international research team have new evidence that an earlier impact could be to blame. Levels of the metal iridium -- which doesn't occur naturally on Earth and only arrives on extraterrestrial objects -- shoot up in rocks from the time when many species died out. Simultaneously, spores of ferns, the first plants to colonize devastated areas, also rise dramatically [1]. Similar evidence from sites worldwide supports the final extinction of dinosaurs by an impact 65 million years ago. Olsen has investigated only one site, the Newark rift basin in eastern North America. Until more evidence is accumulated, some palaeontologists remain cautious. "I tend not to believe it yet," says palaeontologist Mike Benton of the University of Bristol. If people find iridium and spores in other places around the world, "it will become more convincing", he says. Before and after Around 200 million years ago, large plant-eating dinosaurs grazed the Earth alongside primitive meat-eaters as large as ostriches. After the mysterious event that marked the Triassic-Jurassic boundary, herbivores dwindled and large carnivores flourished. The precursors to Tyrannosaurus rex were born. Any explanation for the boundary has to explain why some animals lived when so many others perished. Olsen thinks that only the hardiest creatures would have survived the extreme conditions following an asteroid strike. Dust clouds masking the Sun would have plunged the Earth into cold gloom, followed by intense warming as clouds of greenhouse gases built up. Warm-blooded dinosaurs that could withstand the cold or those that scavenged many food types would have fared best, Olsen suggests. Big feet An alternative explanation is that massive eruptions of volcanic lava, whose ancient remnants have been found, could have caused the mass extinction. For example, gases pumped out with the lava could have cooled the Earth and gradual climate change killed off certain species. Olsen admits he cannot rule this out. But his team does offer additional evidence that the mass extinction at the Triassic- Jurassic boundary was sudden and extreme. This is more consistent with the impact hypothesis. Olsen and his colleagues sifted through sedimentary rocks in several sites in the Newark basin for dinosaur and reptile footprints to find out which animals wandered around when. Previous timing for the extinction was based on sparse fossil finds from around the world. In lakes that were rapidly filling with sediment, a thick layer of rock was laid down in a short period of time. This means that more precise times can be pinned on the disappearance and reappearance of animals. Rocks are dated on the basis of the types of pollen they contain. Half of the animal footprints vanish within as little as 50,000 years, the researchers found, while dinosaur footprints suddenly appear that are up to a fifth larger than before. This time period "is instantaneous on the geological timescale", says geologist Walter Alvarez of the University of California at Berkeley. Alvarez agrees that the weight of evidence now points to an impact as the likely cause of this extinction -- and possibly others too. The rise and demise of dinosaurs are only two of five massive extinctions in world history. "It becomes more likely that they could be impacts too," says Alvarez. References [1] Olsen, P. E. et al. Ascent of dinosaurs linked to iridium anomaly at the Triassic-Jurassic boundary. Science, 296, 1305 - 1307, (2002). © Nature News Service / Macmillan Magazines Ltd 2002 ========== (8) MERCURY METEORITE PUZZLE >From BBC News Online, 16 May 2002 http://news.bbc.co.uk/hi/english/sci/tech/newsid_1991000/1991394.stm By Dr David Whitehouse BBC News Online science editor The first meteorite that may have come from Mercury has been identified. NWA 011 was found in the Moroccan Sahara in December 1999 and was immediately regarded as something unusual. It clearly had a molten past and was formed from lighter materials than most meteorites. This implied it had once been part of a much larger body. It was originally classified as a eucrite, a group of meteorites thought to be from the asteroid Vesta. But a detailed analysis of NWA 011 showed it to be different. Now, researchers speculate that it is the first known meteorite from our Solar System's innermost planet, Mercury. Rocks blasted off Mercury by a large impactor would have a difficult journey to reach the Earth, say the researchers - but not impossible. Nevertheless, the calculations show such rocks would be an extremely rare find on Earth. NWA 011 has an oxygen isotope ratio that indicates it came from a body larger than a big asteroid. Japanese researchers say the basalt in NWA 011 suggests the body from which it did originate had a core of molten iron with an outer covering of silicon and aluminium that formed a basaltic crust. And that means a planet-sized body. Could it really be Mercury? Copyright 2002, BBC (11) IMPACT ODDS >From Michael Paine Dear Benny Andy Smith points out that the odds of Tunguska type impact are about 1 in 100 in the next year. The chances are however that it would happen over ocean or uninhabited land. Based on the one million simulation that I carried out early in 2000, there is roughly a 1 in 300 chance each year of an impact that causes more than 100 fatalities (see table below). The royal flush comparison refers to a major hit by an asteroid perhaps 1.5km across (OK 1 mile) that would cause severe global climate disruption and perhaps a billion fatalities, mostly from crop failures. Somewhere between the two are events that would cause global trauma through the loss of a "significant" city or region, as raised by Jens Kieffer-Olsen in the same CCNet posting. I have reanalysed my one million year simulation to estimate the frequency of fatal events of certain magnitudes. The results are set out below. Note that program was run in 10,000 year increments so it seriously underestimates the number of smaller events. The results, however, a still quite sobering: FATALITIES COUNT P(ANNUAL) RISK >0 3708 0.003708 1 in 269 >100 3221 0.003221 1 in 310 >1000 2800 0.002800 1 in 357 >10,000 1705 0.001705 1 in 586 >100,000 621 0.000621 1 in 1610 >1 Million 180 0.000180 1 in 5555 >10 Million 65 0.000065 1 in 15384 >100 million11 0.000011 1 in 90909 I would expect an event causing 1 million or more fatalities would be quite traumatic for our society, irrespective of where it hit. The annual risk is 1 in 5555 - that's the same as drawing four of a kind in poker! I have added a new graph to my simulation web page at http://www4.tpg.com.au/users/tps-seti/sta1046.htm#fatal_freq On a slightly related matter, in the Budget speech tonight the Australian Treasurer said the government would be spending at least AU$500 million (~200m pounds) "protecting" Australia's borders from asylum seekers (a few hundred boat people in dire circumstances). Now that's what I call a "fruitless, unnecessary, self-indulgent exercise", to use the words of our notorious Science Minister (although "self-indulgent" could be replaced with "selfish"). regards Michael Paine