[meteorite-list] Earthites on the moon
http://www.space.com/scienceastronomy/080626-am-earth-moon.html Bits of Ancient Earth Hidden on the Moon By John Ruley Astrobiology Magazine posted: 26 June 2008 06:55 am ET Some scientists believe that at least one meteorite found in Antarctica preserves evidence of ancient life on Mars. Now, work by a team of English scientists reinforces an earlier suggestion that evidence of life on the early Earth might be found in meteorites on the moon. The original idea was presented in a 2002 paper by University of Washington astronomer John Armstrong, who suggested that material ejected from Earth during the Late Heavy Bombardment (a period about four billion years ago when the Earth was subjected to a rain of asteroids and comets) might be found on the moon. Armstrong's suggestion was interesting, but whether a meteor ejected from the Earth might arrive intact on the moon remained an open question. New research by a team under Ian Crawford and Emily Baldwin of the Birkbeck College School of Earth Sciences used more sophisticated means to simulate the pressures any such terrestrial meteorites might have experienced during their arrival on the lunar surface. This confirmed Armstrong's hypothesis. In many cases, the pressures could be low enough to permit the survival of biological markers, making the lunar surface a good place to look for evidence of early terrestrial life. Any such markers are unlikely to remain on Earth, where they would have been erased long ago by more than three billion years of volcanic activity, later meteor impacts, or simple erosion by wind and rain. Crash landings Given that material from early Mars has been found in meteorites on Earth, it certainly seems reasonable that material from the early Earth could be found on the moon. Indeed, Armstrong's paper estimated that tens of thousands of tons of terrestrial meteorites may have arrived there during the Late Heavy Bombardment. However, there is a problem: The moon lacks any appreciable atmosphere. Meteorites arriving on Earth are decelerated by passing through our atmosphere. As a result, while the surface of the meteorite may melt, the interior is often preserved intact. Could a meteorite from Earth survive a high-velocity impact on the lunar surface? Crawford and Baldwin's analysis, based on commercially available software called AUTDYN, used finite element analysis to simulate the behavior of two different types of meteors impacting the lunar surface. Armstrong's group performed a crude calculation indicating that pressures experienced by a terrestrial meteorite arriving on the moon probably would not be enough to melt it. Crawford and Baldwin's group simulated their meteors as cubes, and calculated pressures at 500 points on the surface of the cube as it impacted the lunar surface at a wide range of impact angles and velocities. In the most extreme case they tested (vertical impact at a speed of some 11,180 mph, or 5 kilometers per second), Crawford reports that some portions of the simulated meteorite would have melted, but the bulk of the projectile, and especially the trailing half, was subjected to much lower pressures. At impact velocities of 2.5 kilometers per second or less, no part of the projectile even approached a peak pressure at which melting would be expected. He concludes that biomarkers ranging from the presence of organic carbon to actual microfossils could have survived the relatively low pressures experienced by the trailing edge of a large meteorite impacting the moon. Hard to find Finding terrestrial meteorites on the moon will be challenging. Crawford suggests that the key to finding terrestrial material is to look for water locked inside. Many minerals on Earth are formed in processes involving water, volcanic activity, or both. By contrast, the moon lacks both water and volcanoes. Minerals formed in the presence of water, called hydrates, can be detected using infrared (IR) spectroscopy. Crawford and his co-authors believe that a high-resolution IR sensor in lunar orbit could be used to detect any large (over one meter) hydrate meteorites on the lunar surface, while a lunar rover with such a sensor could search for smaller meteorites exposed at the surface. Other planetary astronomers view the issue more conservatively. Dr. Mike Gaffey of the University of North Dakota Space Studies department argues that while debris from a large terrestrial impact could have reached the moon ... it's highly unlikely that it would be in sufficient concentrations to be seen using orbital instruments. He believes that the meteorites would be shattered into small pieces by the impact, and then subjected to a form of lunar weathering due to the solar wind and a continuous rain of micrometeoroids that hit the moon. Instead, he suggests that any surviving material from Earth would be fractured into small pieces embedded in ancient lunar soils, some of which might be exposed at the surface by later meteor
Re: [meteorite-list] Earthites
I think that Earthites would have a very high amount of Maskelynite should plagioclase be present in the parent rock. The impacts from earth would be so energetic as to create more of this mineral than in Martian meteorites. The atmospheric composition would then, just as the case with Martian meteorites, reveal that such rocks are indeed from earth and are thus Earthites. Steve Schoner AMS __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Earthites
Steve and List, Thanks for your contribution to this discussion. Your information may help lead to the finding of an Earthite. Best, Dirk Ross...Tokyo --- Steve Schoner [EMAIL PROTECTED] wrote: I think that Earthites would have a very high amount of Maskelynite should plagioclase be present in the parent rock. The impacts from earth would be so energetic as to create more of this mineral than in Martian meteorites. The atmospheric composition would then, just as the case with Martian meteorites, reveal that such rocks are indeed from earth and are thus Earthites. Steve Schoner AMS __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Earthites
List, Which would be the most likely event that potentially could have created an Earthite meteorite? What age would it be? And of what earth rock material and how could it be determined (other than fusion crust)? Would they not be more valuable than Lunites? Thanks for any comments. Dirk Ross..Tokyo __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Earthites
Hi, Ken, List, I've posted on Earthites or terrestrial meteorites a couple of times before; they're somewhere in the archives... Howver. Likely event? More energetic than the impacts that launched the Martian meteorites off Mars, since our atmosphere is thicker, hence harder to get back out through. Likelihood of Earthites? Fairly good, as roughly 50% of the material blasted OFF a planet will likely return to the same planet, according to simulations, as opposed to the 1% to 5% that makes it to another planet. This actually makes it a puzzle as to why there are no examples of an Earthite. Transit times are longish. 10,000 years would be a quick trip. Allow at least 100,000 years to a million years for most, and times up to 10,000,000 years are possible. Many Martians have space exposures of 13,000,000 years... As to what Earthly material it would be, that would depend entirely on the nature of the terrestrial surface that was impacted. And, presumably, tektites are Earthites, but with a short space duration as no CRE exposure can be found in them. I am compelled to opine that Earthites may have been found and discarded as pseudometeorites down through the decades. This is the most likely fate for an Earthite: the trash can. The best case of proof would be a fossiliferous limstone with a fusion crust and a solid long time CRE date; that would be hard to disprove. Then, there's BLECKENSTAD (Sweden, 1925) for which just such an excellent case exists, except that there will be no radiometric dating as the stone was lost long ago (apparently; it couldn't be found in the 1950's). Bleckenstad has impeccable eye-winess reports full of accurate details about meteorite falls that no Swedish peasant farmer would be likely to possess (the whirring noise of a soft-landing meteorite), the fact that the region contains NO native limestones whatsoever, good black fusion crust, and several capable scientists who risked their careers writing about it. It got thrown away anyway... Ninninger found a limestone meteorite while searching for Pasamonte; nobody knows what happened to it. He thought it was a meteorite (fusion crust, thumbprints, and fossils!). There are two West Virginia stones put forward as Earthites. They were never examined on the basis that the whole idea was ridiculous. Their whereabouts are unknown now. See a pattern here? Sterling K. Webb - drtanuki wrote: List, Which would be the most likely event that potentially could have created an Earthite meteorite? What age would it be? And of what earth rock material and how could it be determined (other than fusion crust)? Would they not be more valuable than Lunites? Thanks for any comments. Dirk Ross..Tokyo __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Earthites
Hi, Some scientists are aware of the possibilities and the problems. See (from 1994): http://www.lpi.usra.edu/meetings/programs/desertswa.txt and scroll down to: Wright, I. P.; Grady, M. M.; Pillinger, C. T. The Acquisition of Martian Sedimentary Rocks: For the Time Being, Collection as Meteorites from Terrestrial Desert Areas Represents the Best Hope where they discuss amathosites and calcarites the old terms for limestone meteorites. They are primarily interested in MARTIAN limestones, though. They agree that most linmestone meteorites would be thrown away by museum curators... Interestingly, they dismiss terrestrial meteorites as having no scientific value and of being academic curiosity value only, a rather strange attitude, it seems to me. Hot for Mars, I guess. They cite, on the subject of Earth return, a paper by Melosh, H.J. and Tonks, W.B. (1993), in Meteoritics, 28, 398, but don't quote a title (?). See also simulations by Bret Gladman and his colleagues (got to Google; I don't have the reference handy). As to whether an extraterrestrial meteorite could contain fossils, well, that is just what the argument about the famous Alan Hills Antarctic meteorite is all about! But if I saw fossils in a meteorite, I'd think Earthite! And, recently, a suggestion has been made that the Moon should be a rich source of early Earth rocks older than the oldest recoverable Earth rocks: http://technology.guardian.co.uk/online/science/story/0,12450,870850,00.html and http://www.arn.org/docs/gonzalez/gg_sfchronicle042202.htm For terrestrial meteorites on other planets, see: http://www.meteoritetimes.com/Back_Links/2002/April/Stuarts_Slices.htm For a lot of historical references, mostly to the question of fossils or organic materials in meteorites, see: http://web.mit.edu/afs/athena.mit.edu/user/r/e/redingtn/www/netadv/bioast/clash/pre1950.html The possibility of certain Earthly bacteria being descended from Martian bacteria is discussed in: http://72.14.207.104/search?q=cache:GuHqHEfOYlkJ:biospace.nw.ru/astrobiology/Articles2002/Astrobio_pavlov_25-34.pdf+terrestrial+meteoriteshl=en And so on... Sterling K. Webb - drtanuki wrote: List, Which would be the most likely event that potentially could have created an Earthite meteorite? What age would it be? And of what earth rock material and how could it be determined (other than fusion crust)? Would they not be more valuable than Lunites? Thanks for any comments. Dirk Ross..Tokyo __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
