RE: [meteorite-list] Meteorites on the moon
Hi, Presumably then a similar story is true for Martian meteorites? Any trace of chondritic material in Martians? Mark From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Randy Korotev Sent: 01 September 2006 23:28 To: meteorite-list@meteoritecentral.com Subject: [meteorite-list] Meteorites on the moon Regarding meteorites on the Moon... There is a great deal of meteoritic matter on the Moon, but very few meteorites. The two miniscule fragments that Martin Altmann mentioned are the best known ones from the Apollo collection, but I'm aware of 2 others even smaller. Virtually all meteoroids that strike the Moon either melt or vaporize on impact. If they melt, they mix with the melted silicates of the lunar target rocks. So either way, they become unidentifiable as meteorites. Lunar impact-melt rocks and breccias do contain blebs of meteoritic metal - metal the melted during the impact but as a liquid was immiscible with the molten silicates. All lunar soils and breccias contain meteoritic material. In any handful of lunar soil, 1-4% of the mass is extralunar stuff. Except for blebs of metal, most of which were melted and resolidified, meteorites are virtually absent, however. In the lunar soil, most of the meteoritic material arrives as micrometeorites. By one estimate, approximately 80 grams per square kilometer of micrometeoroids accrete to the Moon (and Earth's atmosphere) each year. We know the meteoritic material (melted and mixed, recondensed from vapor) exists in lunar regolith (soil) and breccias because both are loaded with siderophile (iron-loving) elements like iridium, gold, and platinum in ratios characteristic of chondrites. In contrast, the unbrecciated igneous rocks of the lunar crust - the basalts and anorthosites - have almost immeasurably low concentrations of these elements, as do igneous rocks on Earth. So, every one of the lunar meteorite that is a breccia (which is nearly all of them) contains regular meteoritic material. Those lunar meteorites that are regolith breccias (like NWA 3136 that Adam Hupe mentioned) tend to contain the most. Those that are impact-melt breccias tend to contain the least, judged on the basis of concentrations or, say, iridium. Here's a quote from a paper I've submitted on PCA 02007, a lunar meteorite regolith breccia with a high proportion of chondritic material: The mean Ir concentration of PCA 02007 is equivalent to a component of 2.7% ordinary chondrite or 2.8% CM chondrite. This means that 14% of the Fe and 9% of the Mg and Cr in PCA 02007 derive from extralunar sources (Figs. 8, 9). Day et al. (2006) report an actual meteorite fragment in their thin section of PCA 02007. To my knowledge, the chondrite fragment in a lunar meteorite reported by Day et al. is a first. Randy Korotev __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
RE: [meteorite-list] Meteorites on the moon
Mark, List, There was an article in either Astronomy or Sky and Telescope just a few years ago about how Mars would actually be a GREAT place to find meteorites. I have to leave now and can't search for it, but I'm sure some of the members will remember it. The article essentially stated that the Martian atmosphere was thick enough to prevent cosmic velocity impacts of most meteoroids (unlike on the Moon, which results in vaporization of the impacting body), but not so thick to cause total atmospheric ablation (unlike on Earth). The results would be that MANY meteorites would make it to the surface of Mars. The article even mentioned the estimated number of meteorites per square kilometer that should be visible. I can't recall that number now, but I do remember that it was VERY high. Best wishes, Robert Woolard --- mark ford [EMAIL PROTECTED] wrote: Hi, Presumably then a similar story is true for Martian meteorites? Any trace of chondritic material in Martians? Mark _ __ 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] Meteorites on the moon
Hello Elton and friends: Pandora's meteoritical emotions are clouding this without hope ... You're all too right of course, may I fill up the glass half-way? The atmosphere's viscosity (density) isn't the only thing that determines the entry velocity (besides all the stuff Chris and Sterling too threw in). You forgot cross sectional surface area in the quest for another Cañon Diablo. I'm not sure how minuscule they have to be but those who are into microfossils in paleontology will understand the absolute pleasure of the wondrous world of small things. Instead of pleasuring your tongue to trap snowflakes, you can sample a fine rain of micrometeorites for your delight.* Pull your favorite rare magnets through a confectionary sugar-like earth and assemble pounds of space residue like golden flakes from the Mormon's sandbar. And when you need bigger things, just remember the world doesn't revolve around meteorites...That Tektite Fields are Forever! No aerodynamically sculpted buttons here, but Newton's barrel is alive - kinetic energy rotational and harmonic dancing will make some very ornate Christmas globes. Quaintly collectable goodies from Santa's Tycho Tektite Toy facility --- models including those handsomely wiry striations-texturized globules. And the irradiation could even enhance the chromophores to fluoresce like a spectral kaleidoscope of pearly stars, at least after bedtime as one sleeps ... Best wishes, Doug Perhaps we ought to send all of our meteorites TO the Moon rather than be thinking the other way around. Whether you're Glorieta or just Admire: In this new frontier - All meteorites are curated equally and endowed by their maker with new life and liberty of open assembly for all. *think: your Howardites - Original Message - From: Mr EMan [EMAIL PROTECTED] To: Bob Evans [EMAIL PROTECTED]; Meteorite-list@meteoritecentral.com Sent: Friday, September 01, 2006 12:51 AM Subject: Re: [meteorite-list] Meteorites on the moon Actually, physics-ly speaking, Earth holds far more meteorites than the moon does. Be it remembered, that without an atmosphere to slow them, the bulk of meteoroids arrive at full cosmic speeds and are most certainly vaporized by the collision. I haven't done the math but under an extreme glancing blow where the meteoroid is playing catch up, there might be a successive slowing of splashed fragments and some meteorite material may exist on the surface from time to time. Meteorites that may defy physics in this manner are going to be pulverized into the regolith over time by the constant influx of micrometeoroids. That said, a howardite by definition is composed of substantial clasts of meteoroids from other bodies and they too have arrived at cosmic speeds, so there is hope to find clast on the moon of parent bodies no longer in existence. The moon may be the last repository for discovering the nature of the Early Bombardment episode 3.85 billion years ago. The lunar soil probably contains pockets of meteorite enriched regolith tilled under the surface by contemporary impacts and subsequently tilled back to the surface by recent impacts. This is the impetus to go to the far side for sample returns. I talked once to Charlie Duke --the only geologist thus far to walk on the moon, about the very topic and he said that they did see small furrows where rocks had rolled/bounced along the surface but never the end of a track to see what type rock was sitting there. One small meteorite was recovered in the Apollo Program (Hadley Rill?).(Details anyone?) Didn't it possess impact pockmarks? As to mounting a mission to the moon to recover meteorites, a meteorite not in situ from its parent body may be a curiosity but is far less valuable scientifically than an asteroid sample return mission. I personally would accept either type mission if NASA were willing to send me and bring me back. In fact I have set up a paypal account for donations... for me and my wifeMorganMorgan Fairchild -- yeah that's the ticket... I guess we'll have to wait and see for sure but science suggests that substantial pristine meteorites will be exceedingly rare on the moon. Elton --- Bob Evans [EMAIL PROTECTED] wrote: Can you imagine hunting meteorites on the moon? Crustless Diogenites, Eucrites, Howardites strewnabout everywhere. __ 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
Re: [meteorite-list] Meteorites on the moon
Couple of points One small meteorite was recovered in the Apollo Program (Hadley Rill?).(Details anyone?) Didn't it possess impact pockmarks? Yes. There's one of the Apollo photos clearly shows an ipact mark. A tiny crater in a large rock. I believe this shows that there's not likely to be much of anything left on the moon if it hits it. Statistically, if memory serves me right, lunar impacts impacts are rarer than Earth ones due to the weak gravity of the moon and not just it's smaller cross-section. Rob McC __ 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] Meteorites on the moon
Hi, Rob, List, The ratio of the areas of Earth:Moon is roughly 16:1, but the deflection caused by Earth's stronger gravitational reach makes the ratio of impacts about 18:1. The lunar impact rate is a more accurate measure of the meteroid flux in the vicinity of the Earth's orbit than the Earth's impact rate is, for that reason. Even lunar gravity has a focusing effect in attracting meteroids. The actual space flux of meteroids is calculated to be about 85% to 86% of the rate implied by the impact rate on the Earth. It's much harder to figure out an accurate rate of impacts on the Earth, though. As a result, we have no firm figure to multiply by 0.85. Sterling K. Webb - Original Message - From: Rob McCafferty [EMAIL PROTECTED] To: meteorite-list@meteoritecentral.com Sent: Friday, September 01, 2006 3:01 AM Subject: Re: [meteorite-list] Meteorites on the moon ...lunar impacts are rarer than Earth ones due to the weak gravity of the moon and not just it's smaller cross-section. Rob McC __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites on the moon
Hi Sterling, Rob, List - There is no combined model of asteroid and comet flux which accounts for the observed craters on all bodies in our solar system. The mechanics of the Earth-Moon system have never really been worked out. We really don't know if the Moon gets hit more often than the Earth ot less. Shoemaker, who did a lot of the early Apollo era work, later renounced a lot of it. By the way, no matter what you hear on TV, the impact of a comet killed the dinosaurs, not the impact of an asteroid. thoughts at 4 in the morning, godd hunting, Ed --- Sterling K. Webb [EMAIL PROTECTED] wrote: Hi, Rob, List, The ratio of the areas of Earth:Moon is roughly 16:1, but the deflection caused by Earth's stronger gravitational reach makes the ratio of impacts about 18:1. The lunar impact rate is a more accurate measure of the meteroid flux in the vicinity of the Earth's orbit than the Earth's impact rate is, for that reason. Even lunar gravity has a focusing effect in attracting meteroids. The actual space flux of meteroids is calculated to be about 85% to 86% of the rate implied by the impact rate on the Earth. It's much harder to figure out an accurate rate of impacts on the Earth, though. As a result, we have no firm figure to multiply by 0.85. Sterling K. Webb - Original Message - From: Rob McCafferty [EMAIL PROTECTED] To: meteorite-list@meteoritecentral.com Sent: Friday, September 01, 2006 3:01 AM Subject: Re: [meteorite-list] Meteorites on the moon ...lunar impacts are rarer than Earth ones due to the weak gravity of the moon and not just it's smaller cross-section. Rob McC __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ 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] Meteorites on the moon
Great thread you started Bob. Jerry Flaherty - Original Message - From: Bob Evans [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Sent: Thursday, August 31, 2006 11:54 PM Subject: [meteorite-list] Meteorites on the moon Can you imagine hunting meteorites on the moon? Crustless Diogenites, Eucrites, Howardites strewnabout everywhere. Pristine Pallasites unaltered by atmospheric pressure or humidity sticking out of the lunar dust like a gem. How excited Nasa was when they found one on Mars. I'm surprised there wasn't a manless mission planned to go to the moon to extract and return some of these pristine meteorites utilizing a rover. Obviously it would be tremendously expensive, but, compared to what is spent on the mars mission as well as expeditions in the arctic its a no - brainer. The moon is a meteorite goldmine. 100% impact rates, craters everywhere pinpointing the spot of impact. I wonder if Nasa found one gram out of the relatively miniscule amount of specimens returned from the moon to be of non-lunar origin. I believe if we want to make monumental advancements in Meteoritics we need to take advantage of the abundance on the moon. Who knows what never before seen meteorite types are laying up there right now. What do you think, Mike? You don't have to worry about any Norwegian export laws. __ 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
Re: [meteorite-list] Meteorites on the moon
One small meteorite was recovered in the Apollo Program (Hadley Rill?).(Details anyone?) Didn't it possess impact pockmarks? According to my Meteorites from A to Z (2nd ed.): Bench Crater; CM1 Hadley Rille; EH Already we're finding more than the usual L6 and H5s. However, being exotics, would these rocks have stood out more than the usual Lunar detritus? Both meteorites were pretty tiny, in the under 1g range; I expect they were scooped up in a random sampling of the lunar surface rather than being hunted, i.e., oh look, here's a meteorite! Tracy Latimer __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites on the moon
Unaltered by atmospheric pressure also implies unslowed by any atmosphere. So everything that hits the Moon is doing so at a minimum of around 2.5 km/s, and usually a lot more. I don't think you'll find many meteorites. As thin as the Martian atmosphere is, it is enough to provide aerobraking. The rover cameras have apparently recorded a few meteors. Chris * Chris L Peterson Cloudbait Observatory http://www.cloudbait.com - Original Message - From: Bob Evans [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Sent: Thursday, August 31, 2006 9:54 PM Subject: [meteorite-list] Meteorites on the moon Can you imagine hunting meteorites on the moon? Crustless Diogenites, Eucrites, Howardites strewnabout everywhere. Pristine Pallasites unaltered by atmospheric pressure or humidity sticking out of the lunar dust like a gem. How excited Nasa was when they found one on Mars. I'm surprised there wasn't a manless mission planned to go to the moon to extract and return some of these pristine meteorites utilizing a rover. Obviously it would be tremendously expensive, but, compared to what is spent on the mars mission as well as expeditions in the arctic its a no - brainer. The moon is a meteorite goldmine. 100% impact rates, craters everywhere pinpointing the spot of impact. I wonder if Nasa found one gram out of the relatively miniscule amount of specimens returned from the moon to be of non-lunar origin. I believe if we want to make monumental advancements in Meteoritics we need to take advantage of the abundance on the moon. Who knows what never before seen meteorite types are laying up there right now. What do you think, Mike? You don't have to worry about any Norwegian export laws. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites on the moon
At what velocity do you think Canyon Diablo impacted? I think we found some pieces of that asteroid. - Original Message - From: Chris Peterson [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Sent: Thursday, August 31, 2006 11:06 PM Subject: Re: [meteorite-list] Meteorites on the moon Unaltered by atmospheric pressure also implies unslowed by any atmosphere. So everything that hits the Moon is doing so at a minimum of around 2.5 km/s, and usually a lot more. I don't think you'll find many meteorites. As thin as the Martian atmosphere is, it is enough to provide aerobraking. The rover cameras have apparently recorded a few meteors. Chris * Chris L Peterson Cloudbait Observatory http://www.cloudbait.com - Original Message - From: Bob Evans [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Sent: Thursday, August 31, 2006 9:54 PM Subject: [meteorite-list] Meteorites on the moon Can you imagine hunting meteorites on the moon? Crustless Diogenites, Eucrites, Howardites strewnabout everywhere. Pristine Pallasites unaltered by atmospheric pressure or humidity sticking out of the lunar dust like a gem. How excited Nasa was when they found one on Mars. I'm surprised there wasn't a manless mission planned to go to the moon to extract and return some of these pristine meteorites utilizing a rover. Obviously it would be tremendously expensive, but, compared to what is spent on the mars mission as well as expeditions in the arctic its a no - brainer. The moon is a meteorite goldmine. 100% impact rates, craters everywhere pinpointing the spot of impact. I wonder if Nasa found one gram out of the relatively miniscule amount of specimens returned from the moon to be of non-lunar origin. I believe if we want to make monumental advancements in Meteoritics we need to take advantage of the abundance on the moon. Who knows what never before seen meteorite types are laying up there right now. What do you think, Mike? You don't have to worry about any Norwegian export laws. __ 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
Re: [meteorite-list] Meteorites on the moon
True. Really big chunks might have a tiny percentage of the interior survive. Of course, it isn't likely to be unaltered by the collision (unlike small meteorites found here, which do have unaltered interiors). And irons aren't so interesting. Are there stony meteorites that are the product of hypersonic collisions on Earth? Large impacts are as rare on the Moon as they are on Earth, but of course any debris essentially lasts forever. Chris * Chris L Peterson Cloudbait Observatory http://www.cloudbait.com - Original Message - From: Bob Evans [EMAIL PROTECTED] To: Chris Peterson [EMAIL PROTECTED] Cc: Meteorite-list@meteoritecentral.com Sent: Thursday, August 31, 2006 10:10 PM Subject: Re: [meteorite-list] Meteorites on the moon At what velocity do you think Canyon Diablo impacted? I think we found some pieces of that asteroid. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites on the moon
Hi, Bob, Chris, List The three factors that get a meteorite intact to the surface of the Earth are : a) slow entry velocity, b) low angle of incidence, and c) an aerodynamically useful shape to start with. The third factor is moot on the Moon. The first two still apply. So, some chunk, once in a thousand times, hits low and slow, slow being 5000 to 7000 mph! Of course, the slowing that atmosphere applies is the major cause of the destruction of meteoroids trying to reach the Earth, by heat and a max dynamic pressure which often exceeds the strength of the stone. None of that applies on the Moon, either. Slow or fast, the item will strike the lunar surface unretarded. If the incoming is small and fast, it will vaporize, or at very moderate velocities, be smashed to a fine powder, or some combination of the two. If the incoming is large, the story is different. Think of the stone as having a front pole and a rear pole. The front pole of the stone will vaporize explosively. The shock wave will fragment the rear pole and spall fragments away. The velocity of the shock wave is generally the same as the velocity of impact, but it starts inside the stone, hence gets to the rear pole just in time to spall the last patch of surface off (more if slow; less if fast; nothing if really fast). Bob mentioned Canyon Diablo's. All the Canyon Diablo's that ever were are the result of rear spall. So lunar (meaning on the Moon) meteorites would be a small number of scattered fragments. They would be scattered over a vast landscape (or is that lunascape?) that is itself littered with innumerable lunar crust fragments produced by aeons of bombardment, all pounded to pieces (or to powder). Meteorite hunting on the Moon would be at least as difficult as meteorite hunting on the Earth, like finding a pebble in a rockpile, with neither shape (no aerodynamic friction to sculpt it), nor color (space weathering will alter the colors of the stone) to make any one stone stand out from millions of others. No, make that harder than meteorite hunting on the Earth. Just as on Mars (or anywhere), the likeliest survivor would be a good sized iron (Hoba, Cape York, Wilmette). If it didn't melt on impact or fragment to tiny pieces, someday, someone might notice it... It'll be on the front page of all the newspapers: the Tycho Times, Luna City Ledger, the Copernicus Chronicle... Sterling K. Webb --- - Original Message - From: Chris Peterson [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Sent: Thursday, August 31, 2006 11:06 PM Subject: Re: [meteorite-list] Meteorites on the moon Unaltered by atmospheric pressure also implies unslowed by any atmosphere. So everything that hits the Moon is doing so at a minimum of around 2.5 km/s, and usually a lot more. I don't think you'll find many meteorites. As thin as the Martian atmosphere is, it is enough to provide aerobraking. The rover cameras have apparently recorded a few meteors. Chris * Chris L Peterson Cloudbait Observatory http://www.cloudbait.com - Original Message - From: Bob Evans [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Sent: Thursday, August 31, 2006 9:54 PM Subject: [meteorite-list] Meteorites on the moon Can you imagine hunting meteorites on the moon? Crustless Diogenites, Eucrites, Howardites strewnabout everywhere. Pristine Pallasites unaltered by atmospheric pressure or humidity sticking out of the lunar dust like a gem. How excited Nasa was when they found one on Mars. I'm surprised there wasn't a manless mission planned to go to the moon to extract and return some of these pristine meteorites utilizing a rover. Obviously it would be tremendously expensive, but, compared to what is spent on the mars mission as well as expeditions in the arctic its a no - brainer. The moon is a meteorite goldmine. 100% impact rates, craters everywhere pinpointing the spot of impact. I wonder if Nasa found one gram out of the relatively miniscule amount of specimens returned from the moon to be of non-lunar origin. I believe if we want to make monumental advancements in Meteoritics we need to take advantage of the abundance on the moon. Who knows what never before seen meteorite types are laying up there right now. What do you think, Mike? You don't have to worry about any Norwegian export laws. __ 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
Re: [meteorite-list] Meteorites on the moon
Actually, physics-ly speaking, Earth holds far more meteorites than the moon does. Be it remembered, that without an atmosphere to slow them, the bulk of meteoroids arrive at full cosmic speeds and are most certainly vaporized by the collision. I haven't done the math but under an extreme glancing blow where the meteoroid is playing catch up, there might be a successive slowing of splashed fragments and some meteorite material may exist on the surface from time to time. Meteorites that may defy physics in this manner are going to be pulverized into the regolith over time by the constant influx of micrometeoroids. That said, a howardite by definition is composed of substantial clasts of meteoroids from other bodies and they too have arrived at cosmic speeds, so there is hope to find clast on the moon of parent bodies no longer in existence. The moon may be the last repository for discovering the nature of the Early Bombardment episode 3.85 billion years ago. The lunar soil probably contains pockets of meteorite enriched regolith tilled under the surface by contemporary impacts and subsequently tilled back to the surface by recent impacts. This is the impetus to go to the far side for sample returns. I talked once to Charlie Duke --the only geologist thus far to walk on the moon, about the very topic and he said that they did see small furrows where rocks had rolled/bounced along the surface but never the end of a track to see what type rock was sitting there. One small meteorite was recovered in the Apollo Program (Hadley Rill?).(Details anyone?) Didn't it possess impact pockmarks? As to mounting a mission to the moon to recover meteorites, a meteorite not in situ from its parent body may be a curiosity but is far less valuable scientifically than an asteroid sample return mission. I personally would accept either type mission if NASA were willing to send me and bring me back. In fact I have set up a paypal account for donations... for me and my wifeMorganMorgan Fairchild -- yeah that's the ticket... I guess we'll have to wait and see for sure but science suggests that substantial pristine meteorites will be exceedingly rare on the moon. Elton --- Bob Evans [EMAIL PROTECTED] wrote: Can you imagine hunting meteorites on the moon? Crustless Diogenites, Eucrites, Howardites strewnabout everywhere. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
