[meteorite-list] Question about Meteorites on the Moon
From: EL Jones <jonee_at_meteoritecentral.com>
Date: Thu Apr 22 09:52:22 2004 Message-ID: <3D6AA020.1040303_at_epix.net> <html> <head> </head> <body> <blockquote> Ok Mark and Christopher I'll take a stab I don't know how untechnical I can be.<br> <br> <div>Q1:First he wanted to know if a meteor hits the moon is it technically a meteorite or are only meteors that hit the earth called a meteorite? My answer was that once a meteoroid hits a terrestrial body it is technically a meteorite.</div> <br> A1: Technically under the old distinction a "meteor" can't occur on the moon as a meteor is the flash of light in the atmosphere. IMHO it is a definition that needs updating. I believe when a meteoroid lands on the moon it is a meteorite. In mineral nomenclature the Body e.g. Meteor, Impact, Anthra, is the origin and the suffix -ite..means the physical rock/mineral object from the source. Hence Meteorite, Impactite, and so on. The term "regolyth" is the near equivalent to the term"soil" and is dervied from the pounding of the moon by meteorites/asteroids. The regolyth is also enriched by material from the solar wind and contains more than just meteorites and moon rock.<br> <br> <div>Q2: Second he wanted to know what if any changes would occur to a meteorite once it is on the moon? He is very smart and understands that weathering and a general erosion begins once a meteorite hits the earth due to the actions of our atmosphere, wind and rain. He was wondering if it were common place to go to the moon easily and find meteorites if they would be pristine or would solar winds, and other impacts by space dust, micro meteorites and the such erode them? And if the swings in temperature extremes that can occur on the moon effect them in any way. My answer was that they would probably change a bit over time, but the amount of time that would be needed to cause any changes would be exponentially greater than that of earth.<br> <br> A2: Yes, Yes, and Yes. Chemical recycling and weathering on the moon is much different and would be limited to contact of finely pulverized powders and scant gasses liberated by past volcanos/heating/, gasses,(i.e. sulfites, ammonia, O2, CO , and etc) liberatedfrom meteorites etc. It just isn't a player in the alteration of a meteorite. Appearance-wise there is no fusion crust -- but there may mainly only be meteorite "powder". There is a strong possibility that only the very largest meteorites exist in that collision forces converts the bulk of the meteorites into dust and molten dropplets. Meteorite nodules /shards are likely below the surface unless reexcavated by a subsequent impact. The dust layer on the moon is the 99.99%result of impacts.See Bill Arnet's site on the Moon <a class="moz-txt-link-rfc2396E" href="http://seds.lpl.arizona.edu/nineplanets/nineplanets/luna.html"><http://seds.lpl.arizona.edu/nineplanets/nineplanets/luna.html></a> and Nasa's Apollo Discovery Page <a class="moz-txt-link-rfc2396E" href="http://www.nasm.edu/apollo/apollotop10.htm"><http://www.nasm.edu/apollo/apollotop10.htm></a><br> <br> Moon Dust is composed of angular grains of various sizes and melted glass beads. The dust appears to contain grains of both moon rock and meteorites alike. There are several websites which have photos and descriptions of moon dust. Both the Americans and Russians brought back dust samples. Solar wind and Cosmic rays change the nature of the minerals on the surface. By in large lunar soil is well mixed, churned, and not unlike howardites. <br> <br> The heating cooling cycle on the moon is less destructive due to the lack of water/ice. There is virtually "no heat/cool cycle" transport down slope such as seen by freeze/ thaw on Earth. be it remembered also that lunar rotation is 28± days so the heat/cool (expansion/retraction) cycle is far more gradual than on earth..<br> <br> Q3: The third question he asked was since there is virtually no weather on the moon to stir up dust and bury them meteorites would it be harder to find meteorites on the moon? My answer was that since there is no atmosphere to slow their descent that the impact speed would probably determine whether the meteorites would end up buried deeper in the surface and it would also depend on whether or not they would even survive the impact.<br> <br> A3: No weather but electrostatic forces induced by soalr winds may casue dust to migrate. Seems like I recall some astronauts talking aboutt particles hovering above the ground The dust cloud generated by an impact settles back over the impact hole so there tends to be a blanket of dust on everything. It is cumulative over time. When visiting one of the Surveyor Landers, Apollo Astronauts found very little dust accumulated after 6-8 years, suggesting that the blanket accumulates over eons instead of decades. Lunar gravity may be weaker but it still causes the dust to settle. Moon quakes and impact quakes apparently jar unstable slopes and reduce/flatten crater rims as loose powder creeps downhill . Apollo 16 coring experiments found that the dust/regolyth/soil level exceded 16ft( I think, the maximum length of a core drill with them) The top 2-6 inches were less compacted than further down. Talking to Charlie Duke Jr., Apollo 16 astronaut, and he said they found trails where rocks and or meteorites had rolled and bounced along the surface . I think he said they didn't see any at the end of their trails. I believe he also said that they didn't find any meteorites on that trip. So at least for the bulk of the ride around the rift, meteorites aren't obliviously lying around the surface.<br> <br> Q4: last but not least he asked since the moon is smaller than earth would the density/number of meteorites on the moon be less than that of the earth? My answer was I would ask the experts on this list. (I took the easy way out on that one!) I told him that without an atmosphere to burn up any potential meteors that might hit the moon though it was smaller more would make it to the surface than on earth, but that without that same atmosphere to slow them down, many more would probably not survive the impact and would end up pulverized to dust by the impact.<br> <br> A4: The fact that the Moon shields Earth from meteorites and that Meteoroids burn up 99% of the time, <br> I would say there is more unaltered meteoritic material on the moon I agree with you answer Mark! <br> A bright mind Chris has...you've mentored him well!<br> <br> Regards,<br> Elton<br> </div> <br> <br> <br> <br> <br> </blockquote> </body> </html> Received on Mon 26 Aug 2002 05:39:44 PM PDT |
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