mirrored file at http://SaturnianCosmology.Org/ For complete access to all the files of this collection see http://SaturnianCosmology.org/search.php ========================================================== [1][LINK] [2]Home [3]Table of Contents [4]What's New [5]Image Index [6]Copyright [7]Puzzles [8]Shopping [9]Search [10][LINK] _Asteroid Introduction_ _The future cannot be predicted, but futures can be invented. - Dennis Gabor_ Table of Contents Asteroid Introduction[11]Asteroid Summary Asteroids [12]Annefrank, [13]Braille, [14]Castalia, [15]Eros, [16]Gaspra, [17]Geographos, [18]Ida & Dactyl, [19]Mathilde, [20]Toutatis, [21]Vesta Asteroid Science [22]Asteroid Exploration Chronology[23]Asteroid Image/Animation Gallery[24]Meteoroids and Space Debris Other Resources [25]Asteroid/Comet Impact Hazards[26]NEAR Spacecraft Homepage[27]Asteroid 3753-Earth's Companion[28]Terrestrial Impact Craters[29]Earth Crossing Asteroids [30][LINK] Asteroids are rocky and metallic objects that orbit the Sun but are too small to be considered planets. They are known as _minor planets_. Asteroids range in size from Ceres, which has a diameter of about 1000 km, down to the size of pebbles. Sixteen asteroids have a diameter of 240 km or greater. They have been found inside Earth's orbit to beyond Saturn's orbit. Most, however, are contained within a _main belt_ that exists between the orbits of Mars and Jupiter. Some have orbits that cross Earth's path and some have even hit the Earth in times past. One of the best preserved examples is [31]Barringer Meteor Crater near Winslow, Arizona. Asteroids are material left over from the formation of the solar system. One theory suggests that they are the remains of a planet that was destroyed in a massive collision long ago. More likely, asteroids are material that never coalesced into a planet. In fact, if the estimated total mass of all asteroids was gathered into a single object, the object would be less than 1,500 kilometers (932 miles) across -- less than half the diameter of our Moon. Much of our understanding about asteroids comes from examining pieces of space debris that fall to the surface of Earth. Asteroids that are on a collision course with Earth are called [32]meteoroids. When a meteoroid strikes our atmosphere at high velocity, friction causes this chunk of space matter to incinerate in a streak of light known as a meteor. If the meteoroid does not burn up completely, what's left strikes Earth's surface and is called a meteorite. Of all the meteorites examined, 92.8 percent are composed of silicate (stone), and 5.7 percent are composed of iron and nickel; the rest are a mixture of the three materials. Stony meteorites are the hardest to identify since they look very much like terrestrial rocks. Because asteroids are material from the very early solar system, scientists are interested in their composition. Spacecraft that have flown through the asteroid belt have found that the belt is really quite empty and that asteroids are separated by very large distances. Before 1991 the only information obtained on asteroids was though Earth based observations. Then on October 1991 asteroid [33]951 Gaspra was visited by the [34]Galileo spacecraft and became the first asteroid to have hi-resolution images taken of it. Again on August 1993 Galileo made a close encounter with asteroid [35]243 Ida. This was the second asteroid to be visited by spacecraft. Both Gaspra and Ida are classified as S-type asteroids composed of metal-rich silicates. On June 27, 1997 the spacecraft [36]NEAR made a high-speed close encounter with asteroid [37]253 Mathilde. This encounter gave scientists the first close-up look of a carbon rich C-type asteroid. This visit was unique because NEAR was not designed for flyby encounters. NEAR is an orbiter destined for asteroid Eros in January of 1999. Astronomers have studied a number of asteroids through Earth-based observations. Several notable asteroids are [38]Toutatis, [39]Castalia, [40]Geographos and [41]Vesta. Astronomers studied Toutatis, Geographos and Castalia using Earth-based radar observations during close approaches to the Earth. Vesta was observed by the Hubble Space Telescope. Asteroid Summary Num Name Radius (km) Distance* (10^6km) [42]Albedo Discoverer Date 1 Ceres 466 413.9 0.10 G. Piazzi 1801 511 Davida 168 475.4 0.05 R. Dugan 1903 433 [43]Eros 17.5 x 6.5 218 ? G. Witt, A. Charlois 1893 15 Eunomia 136 395.5 0.19 De Gasparis 1851 52 Europa 156 463.3 0.06 Goldschmidt 1858 951 [44]Gaspra 17x10 330.0 0.20 Neujmin 1916 10 Hygiea 215 470.3 0.08 De Gasparis 1849 243 [45]Ida 58x23 428 ? J. Palisa 29 Sep 1884 704 Interamnia 167 458.1 0.06 V. Cerulli 1910 253 [46]Mathilde 28.5 x 25 396 0.03 J. Palisa 1885 2 Pallas 261 414.5 0.14 H. Olbers 1802 16 Psyche 132 437.1 0.10 De Gasparis 1852 87 Sylvia 136 521.5 0.04 N. Pogson 1866 4 [47]Vesta 262.5 353.4 0.38 H. Olbers 1807 * Mean distance from the Sun. [48]HOME [49]Return to Pluto [50]Visit the Comets _Copyright © 1997-2002 by [51]Calvin J. Hamilton. All rights reserved._ [52]Privacy Statement. [53][LINK] References 1. http://ad.doubleclick.net/jump/sonar.planetscapes/ros;sz=468x60;num=1234567 2. http://www.solarviews.com/eng/homepage.htm 3. http://www.solarviews.com/eng/toc.htm 4. http://www.solarviews.com/eng/new.htm 5. http://www.solarviews.com/cap/index/index.html 6. http://www.solarviews.com/eng/copyright.htm 7. http://crpuzzles.com/ 8. http://www.solarviews.com/store/index.html 9. http://www.solarviews.com/eng/search.htm 10. http://www.solarviews.com/eng/ida.htm 11. file://localhost/www/sat/files/comets/asteroid.htm#asteroid 12. http://www.solarviews.com/eng/annefrank.htm 13. http://www.solarviews.com/eng/braille.htm 14. http://www.solarviews.com/eng/castalia.htm 15. http://www.solarviews.com/eng/eros.htm 16. http://www.solarviews.com/eng/gaspra.htm 17. http://www.solarviews.com/eng/geograph.htm 18. http://www.solarviews.com/eng/ida.htm 19. http://www.solarviews.com/eng/mathilde.htm 20. http://www.solarviews.com/eng/toutatis.htm 21. http://www.solarviews.com/eng/vesta.htm 22. http://www.solarviews.com/eng/craft2.htm#asteroid 23. http://www.solarviews.com/cap/ast/index.htm 24. http://www.solarviews.com/eng/edu/spdebris.htm 25. http://impact.arc.nasa.gov/index.html 26. http://sd-www.jhuapl.edu/NEAR/ 27. http://www.asteroid.yorku.ca/ 28. http://www.solarviews.com/eng/tercrate.htm 29. http://www.eecs.wsu.edu/~hudson/Research/Asteroids/index.htm 30. http://media.fastclick.net/w/click.here?sid=4218&m=3&c=1 31. http://www.solarviews.com/eng/tercrate.htm#meteor 32. http://www.solarviews.com/eng/meteor.htm 33. http://www.solarviews.com/eng/gaspra.htm 34. http://www.solarviews.com/eng/galileo.htm 35. http://www.solarviews.com/eng/ida.htm 36. http://www.solarviews.com/eng/near.htm 37. http://www.solarviews.com/eng/mathilde.htm 38. http://www.solarviews.com/eng/toutatis.htm 39. http://www.solarviews.com/eng/castalia.htm 40. http://www.solarviews.com/eng/geograph.htm 41. http://www.solarviews.com/eng/vesta.htm 42. http://www.solarviews.com/eng/terms.htm#albedo 43. http://www.solarviews.com/eng/eros.htm 44. http://www.solarviews.com/eng/gaspra.htm 45. http://www.solarviews.com/eng/ida.htm 46. http://www.solarviews.com/eng/mathilde.htm 47. http://www.solarviews.com/eng/vesta.htm 48. http://www.solarviews.com/eng/homepage.htm 49. http://www.solarviews.com/eng/pluto.htm 50. http://www.solarviews.com/eng/comet.htm 51. http://www.solarviews.com/eng/author.htm 52. http://www.solarviews.com/eng/privacy.htm 53. http://ad.doubleclick.net/jump/sonar.planetscapes/ros;sz=468x60;num=1234567