Re: [meteorite-list] Witnessed fall lunars?still no clear answere
Hi everyone. You did a good job of thrashing my response without giving an answere to the original question. Why are there no lunar witnessed falls? DR kortev did say there are twice as many Martian impacts,which to me is a lot or many more. Another person questioned if they would have enough velocity to be seen which is a verry good point because some would reach terminal velocity much sooner than an object from mars or the astroid belt. The amount of time recovered lunars take to reach earth has been said to be the same as mars meteorites. I am beginning to believe it may be a matter of recognition. A lunar would reach terminal velocity 20 or more miles up and fall without making a sound. And if it did make a sound the person finding it would do everyones is it a meteorite test. Brown or green crust? Doesnt stick to a magnet.vesicles on the crust. Must not be a meteorite. And what size does it take to launch a rock from the moon?small would do it. Cheers Steve __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Witnessed fall lunars?still no clear answere
I think most of it comes from lack of recognition. Lunar meteorites do not seem to lose as much of their mass when entering the atmosphere so probably do not produce huge bolides. Chondrites, on the other hand generally burn up 90% or more, if they survive at all. For some reason, Martian meteorites tend to be larger in size so probably put out more light. For the most part, they have very black glossy crusts (Eucrite like) which makes them very easy to recognize. The Moroccans have proved that once a searcher has been taught what to look for, success is soon to follow if a reasonable effort is put forth. If I read Randy's site correctly, no lunar meteorites were found in Northwest Africa last year and the peak was around 4 or 5 years ago. Each and every lunar meteorite found in the hot deserts was a tough pull but it can be done. Now that we have gained all of this knowledge from the NWA gold rush which is now over, it is time to work the next plateau which most believe is the Mojave. Happy Hunting, Adam __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Witnessed fall lunars?still no clear answere
Hi Because the people weren't there, when and where they felt, to witness them. General fall rates are a topic for its own, they range in the discussion from a few thousands up to 40,000 falls per year, where a nice stone is really dropped. And each year there are recovered from these thousands of falls always only zero to a dozen. And only the last 200 years meteorite falls were really noticed. http://tin.er.usgs.gov/meteor/ Currently the database has 52000 valid provisional meteorite entries. Means - I don't know - 36566 form Antarctica, average pairing rate let's say 5, 7300 original falls. 1200 witnessed falls. 2000 or so non-desert finds. 12,000 or so desert finds, let's say pairing rate 3... So extremely roughly guessed we have stuff from 15,000 different meteorite falls. Let's look... Antarcica 7000+ different fall events - 19 lunaites and 15 Martians. Oman, where the data are better than with NWA (hopefully not too much pairings will be artificially created? Switzerland?) 2800 numbers 22 lunaites and 4 Martians Falls 1200 0 lunaites and 4 Martians Sooo... observed falls are unsuspicious, regarding the problem that a lunaite wouldn't be recognized in the field, cause it is too similar to terrestrial rocks. Partially Antarctica too as partially the rocks were collected on sheer ice. Therefrom we can speculate, that lunaites fall much more rarely than asteroidial meteorites (id est all the other stuff, without Martians). Hence they are rare per se. With finds, well there we see, that from among 100-350 meteorites found and published meteorites 1 is a lunar. (Perhaps the ratio is even larger...with the desert finds, ordinary chondrites often aren't classified at present). But doesn't matter, that here is totally unscientifical :-) So. 99% of all meteorites aren't lunars (finds, falls stats) 99.9% of all meteorite falls aren't observed. Meteorite falls we tend to witness and to report so far only in a tiny window of 200 years. 1200 witnessed falls we have. This dairymaid calculation - we say here for a naïve fallacy - makes it at least for me plausible, why we haven't any observed lunar fall yet and it doesn't exclude that an observed fall could have happened in past among the 1200 observed ones and it neither excludes that it will happen in future! So I think the reason isn't so much a physical one, but it's only: Chance. Best! Martin -Ursprüngliche Nachricht- Von: meteorite-list-boun...@meteoritecentral.com [mailto:meteorite-list-boun...@meteoritecentral.com] Im Auftrag von Steve Dunklee Gesendet: Mittwoch, 8. September 2010 16:49 An: almi...@localnet.com; meteorite-list@meteoritecentral.com Betreff: Re: [meteorite-list] Witnessed fall lunars?still no clear answere Hi everyone. You did a good job of thrashing my response without giving an answere to the original question. Why are there no lunar witnessed falls? DR kortev did say there are twice as many Martian impacts,which to me is a lot or many more. Another person questioned if they would have enough velocity to be seen which is a verry good point because some would reach terminal velocity much sooner than an object from mars or the astroid belt. The amount of time recovered lunars take to reach earth has been said to be the same as mars meteorites. I am beginning to believe it may be a matter of recognition. A lunar would reach terminal velocity 20 or more miles up and fall without making a sound. And if it did make a sound the person finding it would do everyones is it a meteorite test. Brown or green crust? Doesnt stick to a magnet.vesicles on the crust. Must not be a meteorite. And what size does it take to launch a rock from the moon?small would do it. Cheers Steve __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Witnessed fall lunars?still no clear answere
It could just be dumb chance. Most of the lunars found don't appear to have fallen recently. We might be in a period when, for the couple of hundred years since meteorites started to be recognized for what they are, no lunars arrived where humans were in a position to witness their arrival. My 2 Bessey Specks (which is about all I can afford of planetaries!) Best! Tracy Date: Wed, 8 Sep 2010 07:49:15 -0700 From: steve.dunk...@yahoo.com To: almi...@localnet.com; meteorite-list@meteoritecentral.com Subject: Re: [meteorite-list] Witnessed fall lunars?still no clear answere Hi everyone. You did a good job of thrashing my response without giving an answere to the original question. Why are there no lunar witnessed falls? DR kortev did say there are twice as many Martian impacts,which to me is a lot or many more. Another person questioned if they would have enough velocity to be seen which is a verry good point because some would reach terminal velocity much sooner than an object from mars or the astroid belt. The amount of time recovered lunars take to reach earth has been said to be the same as mars meteorites. I am beginning to believe it may be a matter of recognition. A lunar would reach terminal velocity 20 or more miles up and fall without making a sound. And if it did make a sound the person finding it would do everyones is it a meteorite test. Brown or green crust? Doesnt stick to a magnet.vesicles on the crust. Must not be a meteorite. And what size does it take to launch a rock from the moon?small would do it. Cheers Steve __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Witnessed fall lunars?
escape velocity (2380 m/sec), so when a rock does escape the Moon's gravity, it's in for a wild ride, as it's often going too fast or too slow for where it is. First, to actually escape the Moon, the rock's speed has to be greater than mere escape velocity. Escape velocity will only get you to the Hill Sphere Border. It seems that velocities of 2600 to 2700 meters/sec are needed to actually escape the gravitational environment beyond the Moon's Hill Sphere.. Second, given that you're going fast enough, the one critical factor is the angle at which you leave the Moon's surface. There is one critical angle for each spot on the Moon's surface that guarantees you'll get to Earth if your speed is right. That ideal angle for the minimum possible velocity varies depending on where on the Moon you are, but other angles will do the job if you are going faster. An intriguing conclusion that it is just as easy to get to the Earth from the back side as it is from the front (or facing) side. That means that all our breathless speculation about whether a Lunar meteorite COULD have come from the Backside is wasted. It makes NO DIFFERENCE. Each side is an equally likely source. However, the Eastern Hemisphere is heavily favored, and it seems likely that everything that makes it to the Earth came from the Moon's East Coast. When the rock leaves the East Hemisphere, its velocity is added to the Moon's orbital velocity. If it's pointed right, it's on a fast return trajectory toward the Earth. But if it pops out of the Moon's gravitational control from the West Hemisphere, it's suddenly running too slowly in a retrograde orbit that can't be sustained. It makes a sharp right turn and crashes back into the Moon's surface and makes a new (smaller) crater! If Shute's math is too much for you (show of hands?), skip to the charts and diagrams at the end. They make things much clearer. Shute did numerical integrations to sample impacts, ejecta-producing events, and concludes that as much as 3.3% of the ejecta could get to Earth. Surviving the landing is another matter. (Isn't it always?) After reading this, it's my impression that the Moon likely produces much more material that arrives at the Earth than we usually think it does, and that the short supply of Lunaites is a collection selection effect, as has been suggested. Another impression is that it may only be the more powerful impacts that produce Lunaites. In that case, deliveries to the Earth may only occur at intervals and there may be a multitude of Lunaites delivered from each impact (although they may be scattered), in contrast to the steady rain of meteoroids from far beyond the Earth. I'm too Googled out to check, but is there clustering of the terrestrial ages of Lunaites at irregular intervals? Sterling K. Webb - - Original Message - From: Randy Korotev koro...@wustl.edu To: meteorite-list@meteoritecentral.com Sent: Tuesday, September 07, 2010 4:06 PM Subject: Re: [meteorite-list] Witnessed fall lunars? MikeG asks: Is there a theory for why there have been no witnessed falls of lunar meteorites? It seems odd to me that we have 4 Martian witnessed falls (Shergotty, Chassigny, Zagami, Nakhla, and almost Lafayette) and no lunars. One issue is that these 5 meteorites are 5 kg, 4 kg, 18 kg, 10 kg, and 0.8 kg in mass. Only 3 lunars are 4 kg in mass. Another issue (probably more important) is that lunar escape velocity is only 2.4 km/s and very little material ejected from the Moon is going much faster than that. This velocity compares with 20-40 km/s for asteroidal meteorites. Is a rock entering the atmosphere at 2.4 km/s going to noticeably incandesce? I don't know. I believe that the space shuttle hits the atmosphere at ~7.7 km/s. Melanie asks: I asked this a while ago on Greg Catterton's forum, and I was told that rocks from the moon aren't as solid (tough) as Mars rocks, and therefore are less likely to survive entry... yet what about all these Howardites? Although breccias, most of the lunar meteorites are very tough rocks. Any rock that survives being blasted off the Moon isn't going to disintegrate in Earth's atmosphere any more than an asteroidal or martian meteorite. Steve says: The moon is close to the earth and material knocked off the moon has a relatively short time to reach the earth. Compared to what? Some lunar meteorites took a million years or more to reach Earth. Mars is farther away and not protected by a companion and its closer to the asteroid belt so it receives many more impacts than the moon. Not many more. Only a factor of two greater for Mars, but the average velocity of the impactors is only 60% as great. Randy Korotev Washington University in St. Louis __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list
Re: [meteorite-list] Witnessed fall lunars?
are rusty, like mine, although no doubt Rob Matson will eat it up and ask for please, another bowl, sir? First, the Moon, OUR Moon, is odd. It's a long way from the Earth and its orbital velocity (1022 m/sec) is much slower than its escape velocity (2380 m/sec), so when a rock does escape the Moon's gravity, it's in for a wild ride, as it's often going too fast or too slow for where it is. First, to actually escape the Moon, the rock's speed has to be greater than mere escape velocity. Escape velocity will only get you to the Hill Sphere Border. It seems that velocities of 2600 to 2700 meters/sec are needed to actually escape the gravitational environment beyond the Moon's Hill Sphere.. Second, given that you're going fast enough, the one critical factor is the angle at which you leave the Moon's surface. There is one critical angle for each spot on the Moon's surface that guarantees you'll get to Earth if your speed is right. That ideal angle for the minimum possible velocity varies depending on where on the Moon you are, but other angles will do the job if you are going faster. An intriguing conclusion that it is just as easy to get to the Earth from the back side as it is from the front (or facing) side. That means that all our breathless speculation about whether a Lunar meteorite COULD have come from the Backside is wasted. It makes NO DIFFERENCE. Each side is an equally likely source. However, the Eastern Hemisphere is heavily favored, and it seems likely that everything that makes it to the Earth came from the Moon's East Coast. When the rock leaves the East Hemisphere, its velocity is added to the Moon's orbital velocity. If it's pointed right, it's on a fast return trajectory toward the Earth. But if it pops out of the Moon's gravitational control from the West Hemisphere, it's suddenly running too slowly in a retrograde orbit that can't be sustained. It makes a sharp right turn and crashes back into the Moon's surface and makes a new (smaller) crater! If Shute's math is too much for you (show of hands?), skip to the charts and diagrams at the end. They make things much clearer. Shute did numerical integrations to sample impacts, ejecta-producing events, and concludes that as much as 3.3% of the ejecta could get to Earth. Surviving the landing is another matter. (Isn't it always?) After reading this, it's my impression that the Moon likely produces much more material that arrives at the Earth than we usually think it does, and that the short supply of Lunaites is a collection selection effect, as has been suggested. Another impression is that it may only be the more powerful impacts that produce Lunaites. In that case, deliveries to the Earth may only occur at intervals and there may be a multitude of Lunaites delivered from each impact (although they may be scattered), in contrast to the steady rain of meteoroids from far beyond the Earth. I'm too Googled out to check, but is there clustering of the terrestrial ages of Lunaites at irregular intervals? Sterling K. Webb - - Original Message - From: Randy Korotev koro...@wustl.edu To: meteorite-list@meteoritecentral.com Sent: Tuesday, September 07, 2010 4:06 PM Subject: Re: [meteorite-list] Witnessed fall lunars? MikeG asks: Is there a theory for why there have been no witnessed falls of lunar meteorites? It seems odd to me that we have 4 Martian witnessed falls (Shergotty, Chassigny, Zagami, Nakhla, and almost Lafayette) and no lunars. One issue is that these 5 meteorites are 5 kg, 4 kg, 18 kg, 10 kg, and 0.8 kg in mass. Only 3 lunars are 4 kg in mass. Another issue (probably more important) is that lunar escape velocity is only 2.4 km/s and very little material ejected from the Moon is going much faster than that. This velocity compares with 20-40 km/s for asteroidal meteorites. Is a rock entering the atmosphere at 2.4 km/s going to noticeably incandesce? I don't know. I believe that the space shuttle hits the atmosphere at ~7.7 km/s. Melanie asks: I asked this a while ago on Greg Catterton's forum, and I was told that rocks from the moon aren't as solid (tough) as Mars rocks, and therefore are less likely to survive entry... yet what about all these Howardites? Although breccias, most of the lunar meteorites are very tough rocks. Any rock that survives being blasted off the Moon isn't going to disintegrate in Earth's atmosphere any more than an asteroidal or martian meteorite. Steve says: The moon is close to the earth and material knocked off the moon has a relatively short time to reach the earth. Compared to what? Some lunar meteorites took a million years or more to reach Earth. Mars is farther away and not protected by a companion and its closer to the asteroid belt so it receives many more impacts than
Re: [meteorite-list] Witnessed fall lunars?still no clear answere
Simple but true. Odds favor no witnesses! On Sep 8, 2010, at 12:17 PM, Martin Altmann wrote: Hi Because the people weren't there, when and where they felt, to witness them. General fall rates are a topic for its own, they range in the discussion from a few thousands up to 40,000 falls per year, where a nice stone is really dropped. And each year there are recovered from these thousands of falls always only zero to a dozen. And only the last 200 years meteorite falls were really noticed. http://tin.er.usgs.gov/meteor/ Currently the database has 52000 valid provisional meteorite entries. Means - I don't know - 36566 form Antarctica, average pairing rate let's say 5, 7300 original falls. 1200 witnessed falls. 2000 or so non-desert finds. 12,000 or so desert finds, let's say pairing rate 3... So extremely roughly guessed we have stuff from 15,000 different meteorite falls. Let's look... Antarcica 7000+ different fall events - 19 lunaites and 15 Martians. Oman, where the data are better than with NWA (hopefully not too much pairings will be artificially created? Switzerland?) 2800 numbers 22 lunaites and 4 Martians Falls 1200 0 lunaites and 4 Martians Sooo... observed falls are unsuspicious, regarding the problem that a lunaite wouldn't be recognized in the field, cause it is too similar to terrestrial rocks. Partially Antarctica too as partially the rocks were collected on sheer ice. Therefrom we can speculate, that lunaites fall much more rarely than asteroidial meteorites (id est all the other stuff, without Martians). Hence they are rare per se. With finds, well there we see, that from among 100-350 meteorites found and published meteorites 1 is a lunar. (Perhaps the ratio is even larger...with the desert finds, ordinary chondrites often aren't classified at present). But doesn't matter, that here is totally unscientifical :-) So. 99% of all meteorites aren't lunars (finds, falls stats) 99.9% of all meteorite falls aren't observed. Meteorite falls we tend to witness and to report so far only in a tiny window of 200 years. 1200 witnessed falls we have. This dairymaid calculation - we say here for a naïve fallacy - makes it at least for me plausible, why we haven't any observed lunar fall yet and it doesn't exclude that an observed fall could have happened in past among the 1200 observed ones and it neither excludes that it will happen in future! So I think the reason isn't so much a physical one, but it's only: Chance. Best! Martin -Ursprüngliche Nachricht- Von: meteorite-list-boun...@meteoritecentral.com [mailto:meteorite-list-boun...@meteoritecentral.com] Im Auftrag von Steve Dunklee Gesendet: Mittwoch, 8. September 2010 16:49 An: almi...@localnet.com; meteorite-list@meteoritecentral.com Betreff: Re: [meteorite-list] Witnessed fall lunars?still no clear answere Hi everyone. You did a good job of thrashing my response without giving an answere to the original question. Why are there no lunar witnessed falls? DR kortev did say there are twice as many Martian impacts,which to me is a lot or many more. Another person questioned if they would have enough velocity to be seen which is a verry good point because some would reach terminal velocity much sooner than an object from mars or the astroid belt. The amount of time recovered lunars take to reach earth has been said to be the same as mars meteorites. I am beginning to believe it may be a matter of recognition. A lunar would reach terminal velocity 20 or more miles up and fall without making a sound. And if it did make a sound the person finding it would do everyones is it a meteorite test. Brown or green crust? Doesnt stick to a magnet.vesicles on the crust. Must not be a meteorite. And what size does it take to launch a rock from the moon?small would do it. Cheers Steve __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Witnessed fall lunars?
Hi, I asked this a while ago on Greg Catterton's forum, and I was told that rocks from the moon aren't as solid (tough) as Mars rocks, and therefore are less likely to survive entry... yet what about all these Howardites? --- -Melanie IMCA: 2975 eBay: metmel2775 Known on SkyRock Cafe as SpaceCollector09 I eat, sleep and breath meteorites 24/7. - Original Message From: Galactic Stone Ironworks meteoritem...@gmail.com To: Meteorite List meteorite-list@meteoritecentral.com Sent: Mon, September 6, 2010 2:05:16 PM Subject: [meteorite-list] Witnessed fall lunars? Hi List, Is there a theory for why there have been no witnessed falls of lunar meteorites? It seems odd to me that we have 4 Martian witnessed falls (Shergotty, Chassigny, Zagami, Nakhla, and almost Lafayette) and no lunars. I also find it odd that no lunaites have been recovered from the Americas or Europe. It would seem that we are long overdue for two things to happen - for a lunaite to be recovered in the Americas/Europe and for a lunar witnessed fall. I wonder which will happen first? Best regards, MikeG -- -- Mike Gilmer - Galactic Stone Ironworks Meteorites Website - http://www.galactic-stone.com Facebook - http://www.facebook.com/galacticstone News Feed - http://www.galactic-stone.com/rss/126516 Twitter - http://twitter.com/galacticstone EOM - http://www.encyclopedia-of-meteorites.com/collection.aspx?id=1564 --- __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Witnessed fall lunars?
-destructive... Yes lunaites are striking, they own magic. But the same is valid for all other types. Where has all the spirit gone... (Sterling will say: Spirit? Spirit is currently on Mars!. Yes it is. But also - what can we do so much more, with a Martian rock, if we have it here in our labs on Earth!) Huh, what a chesy, cheesy end of that much too long boring post. And so what. Off. Must go to fondle a lunaite. Best! Martin -Ursprüngliche Nachricht- Von: meteorite-list-boun...@meteoritecentral.com [mailto:meteorite-list-boun...@meteoritecentral.com] Im Auftrag von Galactic Stone Ironworks Gesendet: Montag, 6. September 2010 23:05 An: Meteorite List Betreff: [meteorite-list] Witnessed fall lunars? Hi List, Is there a theory for why there have been no witnessed falls of lunar meteorites? It seems odd to me that we have 4 Martian witnessed falls (Shergotty, Chassigny, Zagami, Nakhla, and almost Lafayette) and no lunars. I also find it odd that no lunaites have been recovered from the Americas or Europe. It would seem that we are long overdue for two things to happen - for a lunaite to be recovered in the Americas/Europe and for a lunar witnessed fall. I wonder which will happen first? Best regards, MikeG __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Witnessed fall lunars?
The moon is close to the earth and material knocked off the moon has a relatively short time to reach the earth. The moon is also protected by the earth. So there will be less material floating around to fall as meteorites. Mars is farther away and not protected by a companion and its closer to the astroid belt so it recieves many more impacts than the moon. Its kind of like paintball. The guy close to you hiding behind the tree the moon gets hit a lot less than the guy standing out in the openMars less hits less meteorites. Cheers! Steve __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Witnessed fall lunars?
MikeG asks: Is there a theory for why there have been no witnessed falls of lunar meteorites? It seems odd to me that we have 4 Martian witnessed falls (Shergotty, Chassigny, Zagami, Nakhla, and almost Lafayette) and no lunars. One issue is that these 5 meteorites are 5 kg, 4 kg, 18 kg, 10 kg, and 0.8 kg in mass. Only 3 lunars are 4 kg in mass. Another issue (probably more important) is that lunar escape velocity is only 2.4 km/s and very little material ejected from the Moon is going much faster than that. This velocity compares with 20-40 km/s for asteroidal meteorites. Is a rock entering the atmosphere at 2.4 km/s going to noticeably incandesce? I don't know. I believe that the space shuttle hits the atmosphere at ~7.7 km/s. Melanie asks: I asked this a while ago on Greg Catterton's forum, and I was told that rocks from the moon aren't as solid (tough) as Mars rocks, and therefore are less likely to survive entry... yet what about all these Howardites? Although breccias, most of the lunar meteorites are very tough rocks. Any rock that survives being blasted off the Moon isn't going to disintegrate in Earth's atmosphere any more than an asteroidal or martian meteorite. Steve says: The moon is close to the earth and material knocked off the moon has a relatively short time to reach the earth. Compared to what? Some lunar meteorites took a million years or more to reach Earth. Mars is farther away and not protected by a companion and its closer to the asteroid belt so it receives many more impacts than the moon. Not many more. Only a factor of two greater for Mars, but the average velocity of the impactors is only 60% as great. Randy Korotev Washington University in St. Louis __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Witnessed fall lunars?
On Tue, 07 Sep 2010 16:06:15 -0500, you wrote: Another issue (probably more important) is that lunar escape velocity is only 2.4 km/s and very little material ejected from the Moon is going much faster than that. This velocity compares with 20-40 km/s for asteroidal meteorites. Is a rock entering the atmosphere at 2.4 km/s going to noticeably incandesce? I don't know. The minimum velocity of a meteor entering the Earth's atmosphere is Earth's escape velocity of 11.2 km/s. The escape velocity of the parent body is irrelevant. http://www.google.com/#hl=ensource=hpq=minimum+speed+meteoraq=faqi=aql=oq=gs_rfai=CvX3Z76yGTOLhPIOIyAStwKCTBQAAAKoEBU_QhF8-pbx=1fp=983d1b7d11262f2f __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Witnessed fall lunars?
Hi Dr. Korotev and all, I appreciate your lunar website and often refer to it. Glad you are a participant here. If that is the case then lunar meteorites would have to heat up quite a little bit due to this slower speed. How altered would material be then from the fall? perhaps the ablating process is enough to keep the material relitively cool with out altering the material significantly. As the material approaches Earth it should speed up due to gravity. It's a down hill trip from the moon after a certain point (about 1/3 way toward the Earth). I've heard only a small percentage actually reaches the Earth due to physical dynamics. Best! --AL Mitterling Quoting Randy Korotev koro...@wustl.edu: MikeG asks: Is there a theory for why there have been no witnessed falls of lunar meteorites? It seems odd to me that we have 4 Martian witnessed falls (Shergotty, Chassigny, Zagami, Nakhla, and almost Lafayette) and no lunars. One issue is that these 5 meteorites are 5 kg, 4 kg, 18 kg, 10 kg, and 0.8 kg in mass. Only 3 lunars are 4 kg in mass. Another issue (probably more important) is that lunar escape velocity is only 2.4 km/s and very little material ejected from the Moon is going much faster than that. This velocity compares with 20-40 km/s for asteroidal meteorites. Is a rock entering the atmosphere at 2.4 km/s going to noticeably incandesce? I don't know. I believe that the space shuttle hits the atmosphere at ~7.7 km/s. Melanie asks: I asked this a while ago on Greg Catterton's forum, and I was told that rocks from the moon aren't as solid (tough) as Mars rocks, and therefore are less likely to survive entry... yet what about all these Howardites? Although breccias, most of the lunar meteorites are very tough rocks. Any rock that survives being blasted off the Moon isn't going to disintegrate in Earth's atmosphere any more than an asteroidal or martian meteorite. Steve says: The moon is close to the earth and material knocked off the moon has a relatively short time to reach the earth. Compared to what? Some lunar meteorites took a million years or more to reach Earth. Mars is farther away and not protected by a companion and its closer to the asteroid belt so it receives many more impacts than the moon. Not many more. Only a factor of two greater for Mars, but the average velocity of the impactors is only 60% as great. Randy Korotev Washington University in St. Louis __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Witnessed fall lunars?
or too slow for where it is. First, to actually escape the Moon, the rock's speed has to be greater than mere escape velocity. Escape velocity will only get you to the Hill Sphere Border. It seems that velocities of 2600 to 2700 meters/sec are needed to actually escape the gravitational environment beyond the Moon's Hill Sphere.. Second, given that you're going fast enough, the one critical factor is the angle at which you leave the Moon's surface. There is one critical angle for each spot on the Moon's surface that guarantees you'll get to Earth if your speed is right. That ideal angle for the minimum possible velocity varies depending on where on the Moon you are, but other angles will do the job if you are going faster. An intriguing conclusion that it is just as easy to get to the Earth from the back side as it is from the front (or facing) side. That means that all our breathless speculation about whether a Lunar meteorite COULD have come from the Backside is wasted. It makes NO DIFFERENCE. Each side is an equally likely source. However, the Eastern Hemisphere is heavily favored, and it seems likely that everything that makes it to the Earth came from the Moon's East Coast. When the rock leaves the East Hemisphere, its velocity is added to the Moon's orbital velocity. If it's pointed right, it's on a fast return trajectory toward the Earth. But if it pops out of the Moon's gravitational control from the West Hemisphere, it's suddenly running too slowly in a retrograde orbit that can't be sustained. It makes a sharp right turn and crashes back into the Moon's surface and makes a new (smaller) crater! If Shute's math is too much for you (show of hands?), skip to the charts and diagrams at the end. They make things much clearer. Shute did numerical integrations to sample impacts, ejecta-producing events, and concludes that as much as 3.3% of the ejecta could get to Earth. Surviving the landing is another matter. (Isn't it always?) After reading this, it's my impression that the Moon likely produces much more material that arrives at the Earth than we usually think it does, and that the short supply of Lunaites is a collection selection effect, as has been suggested. Another impression is that it may only be the more powerful impacts that produce Lunaites. In that case, deliveries to the Earth may only occur at intervals and there may be a multitude of Lunaites delivered from each impact (although they may be scattered), in contrast to the steady rain of meteoroids from far beyond the Earth. I'm too Googled out to check, but is there clustering of the terrestrial ages of Lunaites at irregular intervals? Sterling K. Webb - - Original Message - From: Randy Korotev koro...@wustl.edu To: meteorite-list@meteoritecentral.com Sent: Tuesday, September 07, 2010 4:06 PM Subject: Re: [meteorite-list] Witnessed fall lunars? MikeG asks: Is there a theory for why there have been no witnessed falls of lunar meteorites? It seems odd to me that we have 4 Martian witnessed falls (Shergotty, Chassigny, Zagami, Nakhla, and almost Lafayette) and no lunars. One issue is that these 5 meteorites are 5 kg, 4 kg, 18 kg, 10 kg, and 0.8 kg in mass. Only 3 lunars are 4 kg in mass. Another issue (probably more important) is that lunar escape velocity is only 2.4 km/s and very little material ejected from the Moon is going much faster than that. This velocity compares with 20-40 km/s for asteroidal meteorites. Is a rock entering the atmosphere at 2.4 km/s going to noticeably incandesce? I don't know. I believe that the space shuttle hits the atmosphere at ~7.7 km/s. Melanie asks: I asked this a while ago on Greg Catterton's forum, and I was told that rocks from the moon aren't as solid (tough) as Mars rocks, and therefore are less likely to survive entry... yet what about all these Howardites? Although breccias, most of the lunar meteorites are very tough rocks. Any rock that survives being blasted off the Moon isn't going to disintegrate in Earth's atmosphere any more than an asteroidal or martian meteorite. Steve says: The moon is close to the earth and material knocked off the moon has a relatively short time to reach the earth. Compared to what? Some lunar meteorites took a million years or more to reach Earth. Mars is farther away and not protected by a companion and its closer to the asteroid belt so it receives many more impacts than the moon. Not many more. Only a factor of two greater for Mars, but the average velocity of the impactors is only 60% as great. Randy Korotev Washington University in St. Louis __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Witnessed fall lunars?
Mars is farther away and not protected by a companion and its closer to the asteroid belt so it receives many more impacts than the moon. Not many more. Only a factor of two greater for Mars, but the average velocity of the impactors is only 60% as great. To add, the side of the Moon that always faces away from Earth would be just as vulnerable to bombardment as Mars is.. --- -Melanie IMCA: 2975 eBay: metmel2775 Known on SkyRock Cafe as SpaceCollector09 I eat, sleep and breath meteorites 24/7. - Original Message From: Randy Korotev koro...@wustl.edu To: meteorite-list@meteoritecentral.com Sent: Tue, September 7, 2010 2:06:15 PM Subject: Re: [meteorite-list] Witnessed fall lunars? MikeG asks: Is there a theory for why there have been no witnessed falls of lunar meteorites? It seems odd to me that we have 4 Martian witnessed falls (Shergotty, Chassigny, Zagami, Nakhla, and almost Lafayette) and no lunars. One issue is that these 5 meteorites are 5 kg, 4 kg, 18 kg, 10 kg, and 0.8 kg in mass. Only 3 lunars are 4 kg in mass. Another issue (probably more important) is that lunar escape velocity is only 2.4 km/s and very little material ejected from the Moon is going much faster than that. This velocity compares with 20-40 km/s for asteroidal meteorites. Is a rock entering the atmosphere at 2.4 km/s going to noticeably incandesce? I don't know. I believe that the space shuttle hits the atmosphere at ~7.7 km/s. Melanie asks: I asked this a while ago on Greg Catterton's forum, and I was told that rocks from the moon aren't as solid (tough) as Mars rocks, and therefore are less likely to survive entry... yet what about all these Howardites? Although breccias, most of the lunar meteorites are very tough rocks. Any rock that survives being blasted off the Moon isn't going to disintegrate in Earth's atmosphere any more than an asteroidal or martian meteorite. Steve says: The moon is close to the earth and material knocked off the moon has a relatively short time to reach the earth. Compared to what? Some lunar meteorites took a million years or more to reach Earth. Mars is farther away and not protected by a companion and its closer to the asteroid belt so it receives many more impacts than the moon. Not many more. Only a factor of two greater for Mars, but the average velocity of the impactors is only 60% as great. Randy Korotev Washington University in St. Louis __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Witnessed fall lunars?
Hi List, Is there a theory for why there have been no witnessed falls of lunar meteorites? It seems odd to me that we have 4 Martian witnessed falls (Shergotty, Chassigny, Zagami, Nakhla, and almost Lafayette) and no lunars. I also find it odd that no lunaites have been recovered from the Americas or Europe. It would seem that we are long overdue for two things to happen - for a lunaite to be recovered in the Americas/Europe and for a lunar witnessed fall. I wonder which will happen first? Best regards, MikeG -- -- Mike Gilmer - Galactic Stone Ironworks Meteorites Website - http://www.galactic-stone.com Facebook - http://www.facebook.com/galacticstone News Feed - http://www.galactic-stone.com/rss/126516 Twitter - http://twitter.com/galacticstone EOM - http://www.encyclopedia-of-meteorites.com/collection.aspx?id=1564 --- __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Witnessed fall lunars?
This might be one. http://cgi.ebay.com/North-American-Lunar-Meteorite-/120618283540?pt=LH_Defau ltDomain_0hash=item1c1568f214 Michael On 9/6/10 2:05 PM, Met. Michael Gilmer meteoritem...@gmail.com wrote: Hi List, Is there a theory for why there have been no witnessed falls of lunar meteorites? It seems odd to me that we have 4 Martian witnessed falls (Shergotty, Chassigny, Zagami, Nakhla, and almost Lafayette) and no lunars. I also find it odd that no lunaites have been recovered from the Americas or Europe. It would seem that we are long overdue for two things to happen - for a lunaite to be recovered in the Americas/Europe and for a lunar witnessed fall. I wonder which will happen first? Best regards, MikeG __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Witnessed fall lunars?
That's amazing for only $1.7 million! Makes my volcanic breccia from the North Cascades look real good. Rob H. -- From: Michael Blood mlbl...@cox.net Sent: Monday, September 06, 2010 10:35 PM To: Met. Michael Gilmer meteoritem...@gmail.com; Meteorite List meteorite-list@meteoritecentral.com Subject: Re: [meteorite-list] Witnessed fall lunars? This might be one. http://cgi.ebay.com/North-American-Lunar-Meteorite-/120618283540?pt=LH_Defau ltDomain_0hash=item1c1568f214 Michael On 9/6/10 2:05 PM, Met. Michael Gilmer meteoritem...@gmail.com wrote: Hi List, Is there a theory for why there have been no witnessed falls of lunar meteorites? It seems odd to me that we have 4 Martian witnessed falls (Shergotty, Chassigny, Zagami, Nakhla, and almost Lafayette) and no lunars. I also find it odd that no lunaites have been recovered from the Americas or Europe. It would seem that we are long overdue for two things to happen - for a lunaite to be recovered in the Americas/Europe and for a lunar witnessed fall. I wonder which will happen first? Best regards, MikeG __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
