RE: [meteorite-list] Recognizing a Venusian meteorite
More to the point where are all the earth meteorites? We should be able to recognize them, (one would hope!), I guess as most of the earths immediate surface is soil, or sedimentary rock(s), an earthite meteorite would be pretty strange do date no true 'sedimentary' meteorites have been found?, I guess it would probably look like a tektite I.e silica glass... or would they be just be highly shocked ordinary terrestrial rocks but with a fusion crust? Mark Ford __ Meteorite-list mailing list [EMAIL PROTECTED] http://www.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Recognizing a Venusian meteorite
Considering that all the extrasolar planets we have found so far have been gas giants, and some in highly weird orbits to boot, maybe Earth _is_ an anomaly, astrophysically speaking. Of course, our means of locating smaller planets isn't as effective, yet. Possibly being smacked by whatever tore loose the moon (according to recent theory) was the best thing that could have happened to us -- for life formation, that is. Tracy Latimer From: Sterling K. Webb [EMAIL PROTECTED] To: [EMAIL PROTECTED] CC: [EMAIL PROTECTED] Subject: Re: [meteorite-list] Recognizing a Venusian meteorite Date: Fri, 24 Oct 2003 00:09:39 -0500 Gee, You mean, we could have been a nice normal planet like Venus if it wasn't for the sheer bad luck of getting that ol' Devil Moon delivered to our doorstep? _ Never get a busy signal because you are always connected with high-speed Internet access. Click here to comparison-shop providers. https://broadband.msn.com __ Meteorite-list mailing list [EMAIL PROTECTED] http://www.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Recognizing a Venusian meteorite
Howard Wu wrote: Still the question was how would we recognize a venusian meteorite? Great question to ponder. As a lay astrogeologist here is an answer as I see it. So far we only have the direct sampling of the Venusian atmosphere by the Soviet mission. The isotope ratios of the Venusian atmosphere will help in confirming meteorites from the Mercury Venus Zone. The analysis will initially lie in the differences in isotopic ratios between Mars and Venus, I feel. Age of formation will be equally important. We need a mission to Venus again! We know that there is a gradient of heavy to light elements produced by a presolar shockwave(s) that swept elements outward from the center. This is why the inner planets are stony-irons and the outer ones are gaseous. Having higher momentum / inertiamoments, the heavier elements tended to remain in the inner solar system while lighter elements rode the bow wave to the outer edges. Of course all the atoms of each element were not completely segregated, none-the -less there was a measurable sorting. We know this from measuring values against the elemental abundance of the solar system. Theelemental abundance is a calculation of all elements against each other such that we know the ratio of each individual element to all the others or, in another way, we know their individual percentage in the entire mass of the soar system. Along with the afore mentioned distribution/concentration of elements, is a subset distribution within the isotopes of individual elements. For example, from each area of concentration in the solar system for oxygen, the ratio of isotopes such as Oxygen 16, 17, and 18 as they relate to each other vary. Specifically, they vary with the distance they are from the center of the solar system. The lighter the isotope, the more distantly it moved toward the outer edge of the solar system. The Earth Moon ratio has been determined. This is one of the means we used to identify lunar meteorites. Similar ratios were used to identify Martian meteorites based on Viking Lander measurements. Igneous rocks from Earth and Mars pretty much contain the same minerals so we rely on isotopic ratios and radioisotope ages to shore up our findings. In like manner, that is how the determination of a Veneusian meteorite will happen. While the jurry is out on Mercury, some think it was captured and its orbit of formation lies elsewhere, (isotopic ratios may not be what is expected from a planetoid forming close to the solar center), Venus is another story. It is certianly a differenteated body and recently volcanicaly active. Any Enstatite chondrite (E,EH,EL) can't be from Mercury nor Venus. Likewise the age of formation/crystallization for Venuisan material will likely be much less younger than asteroidal material. So Venusian material will likely be isotopically weighted toward Oxygen 18 and will have a crystallization age closer to Martian material but I am guessing under 2 but less than 3-3.5 billion years. Regards, Elton __ Meteorite-list mailing list [EMAIL PROTECTED] http://www.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Recognizing a Venusian meteorite
E.J wrote: Howard Wu wrote: Still the question was how would we recognize a venusian meteorite? Great question to ponder. The best way to identify a Venus Stone would be by the Argon isotope ratios. Argon-36 is the natural original isotope of Argon from the solar nebula. Argon-40 is formed by the radioactive decay of Potassium. It forms in the stone body of a planet and is released to the atmosphere by volcanic action, or out-gassing. On Earth, most of our Argon is isotope 40, thanks to our active little rockball, and there is very little natural Argon. The 40:36 isotope ratio is 296 to 1. On Mars, there is even less natural Argon. The 40:36 isotope ratio for Mars is 2750 +/- 500 to 1 (Is Mars more volcanic than the Earth? H.). So far, it all fits with those nice theories about volatiles and nebulas (which, you call tell by my tone, I distrust profoundly). Therefore, we would expect a ratio of 200:1 for Venus or maybe even 100:1, right? Here's where reality gets in its licks. First, there's 50 to 100 times more Argon and Neon in Venus' atmosphere than we would expect, huge amounts! Where in the H*** did that come from? Second, the 40:36 isotope ratio is 1 to 1, more or less. That is, they are present in roughly equal amounts. Say what? Well, maybe all the noble gasses are enriched? Nah, they're not. This demonstrates that the abnormal Argon did not come from the old solar nebula. The two explanations left and they're both whacky: 1) Venus has no Potassium in the planet at all, so there is no Argon 40! This goes against everything. No Potassium!!! That's Crazy. And 2) Venus has never had any kind of volcanic activity at all, ever, period. That's even Crazier, since we can radar-map a huge of what appear to be volcanic features on Venus. My personal theory is that Venus had its entire native atmosphere blown off by a whopping big impactor 480,000,000 years ago, an impactor that completely melted Venus' crust, resurfaced the planet, and left a lot of its own volatiles behind as a new atmosphere to mix with the residues of the melted crust. Hey, I said it was whopping big, didn't I? So, what you do is a rare gas analysis of the suspected Venus meteorite, and if the Argon 40:36 ratio is the same, then Venusian meteorite is its name, as Johnny Cochran would say. Sterling K. Webb -- As a lay astrogeologist here is an answer as I see it. So far we only have the direct sampling of the Venusian atmosphere by the Soviet mission. The isotope ratios of the Venusian atmosphere will help in confirming meteorites from the Mercury Venus Zone. The analysis will initially lie in the differences in isotopic ratios between Mars and Venus, I feel. Age of formation will be equally important. We need a mission to Venus again! We know that there is a gradient of heavy to light elements produced by a presolar shockwave(s) that swept elements outward from the center. This is why the inner planets are stony-irons and the outer ones are gaseous. Having higher momentum / inertiamoments, the heavier elements tended to remain in the inner solar system while lighter elements rode the bow wave to the outer edges. Of course all the atoms of each element were not completely segregated, none-the -less there was a measurable sorting. We know this from measuring values against the elemental abundance of the solar system. Theelemental abundance is a calculation of all elements against each other such that we know the ratio of each individual element to all the others or, in another way, we know their individual percentage in the entire mass of the soar system. Along with the afore mentioned distribution/concentration of elements, is a subset distribution within the isotopes of individual elements. For example, from each area of concentration in the solar system for oxygen, the ratio of isotopes such as Oxygen 16, 17, and 18 as they relate to each other vary. Specifically, they vary with the distance they are from the center of the solar system. The lighter the isotope, the more distantly it moved toward the outer edge of the solar system. The Earth Moon ratio has been determined. This is one of the means we used to identify lunar meteorites. Similar ratios were used to identify Martian meteorites based on Viking Lander measurements. Igneous rocks from Earth and Mars pretty much contain the same minerals so we rely on isotopic ratios and radioisotope ages to shore up our findings. In like manner, that is how the determination of a Veneusian meteorite will happen. While the jurry is out on Mercury, some think it was captured and its orbit of formation lies elsewhere, (isotopic ratios may not be what is expected from a planetoid forming close to the solar center), Venus is another story. It is certianly a differenteated body and recently volcanicaly active. Any Enstatite chondrite (E,EH,EL) can't be from
[meteorite-list] Recognizing a Venusian meteorite
Sterling, Interesting theory about Venus's atmosphere being blown off by a monster impactor. Here is my objection: Where did the 100 bar carbon dioxide atmosphere come from? Could one monster impactor blow off the existing atmosphere and yet at the same time deposit a new one? Seems a stretch. I suggest a different scenario. Mars is enriched in Argon 40 compared to earth for the same reason it is enriched in deuterium. The lighter elements are lost to space as a function of Mars's lesser gravity. Venus has a tremendous amount of CO2, Argon 36 neon, etc, because it atmosphere was not blown off into space by a giant impactor. On the contrary it was earth's atmosphere that was lost to space. Therefore using Earth's ratio of Ar 36/40 as a standard is misleading. What was the giant impactor responsible for the loss of earth's atmosphere. A good candidate is the impactor that created the moon. In any case, a young crystallization age of less than 500 million years would eliminate all sources, except Venus and Mars. Mike Fowler E.J wrote: Howard Wu wrote: Still the question was how would we recognize a venusian meteorite? Great question to ponder. The best way to identify a Venus Stone would be by the Argon isotope ratios. Argon-36 is the natural original isotope of Argon from the solar nebula. Argon-40 is formed by the radioactive decay of Potassium. It forms in the stone body of a planet and is released to the atmosphere by volcanic action, or out-gassing. On Earth, most of our Argon is isotope 40, thanks to our active little rockball, and there is very little natural Argon. The 40:36 isotope ratio is 296 to 1. On Mars, there is even less natural Argon. The 40:36 isotope ratio for Mars is 2750 +/- 500 to 1 (Is Mars more volcanic than the Earth? H.). So far, it all fits with those nice theories about volatiles and nebulas (which, you call tell by my tone, I distrust profoundly). Therefore, we would expect a ratio of 200:1 for Venus or maybe even 100:1, right? Here's where reality gets in its licks. First, there's 50 to 100 times more Argon and Neon in Venus' atmosphere than we would expect, huge amounts! Where in the H*** did that come from? Second, the 40:36 isotope ratio is 1 to 1, more or less. That is, they are present in roughly equal amounts. Say what? Well, maybe all the noble gasses are enriched? Nah, they're not. This demonstrates that the abnormal Argon did not come from the old solar nebula. The two explanations left and they're both whacky: 1) Venus has no Potassium in the planet at all, so there is no Argon 40! This goes against everything. No Potassium!!! That's Crazy. And 2) Venus has never had any kind of volcanic activity at all, ever, period. That's even Crazier, since we can radar-map a huge of what appear to be volcanic features on Venus. My personal theory is that Venus had its entire native atmosphere blown off by a whopping big impactor 480,000,000 years ago, an impactor that completely melted Venus' crust, resurfaced the planet, and left a lot of its own volatiles behind as a new atmosphere to mix with the residues of the melted crust. Hey, I said it was whopping big, didn't I? So, what you do is a rare gas analysis of the suspected Venus meteorite, and if the Argon 40:36 ratio is the same, then Venusian meteorite is its name, as Johnny Cochran would say. Sterling K. Webb __ Meteorite-list mailing list [EMAIL PROTECTED] http://www.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Recognizing a Venusian meteorite
Gee, You mean, we could have been a nice normal planet like Venus if it wasn't for the sheer bad luck of getting that ol' Devil Moon delivered to our doorstep? Shucks, I hate to think of having to miss those 100-bar CO2 breezes, particularly the ones with that whiff of fresh Argon, when I get up in the morning and trundle down to the nearest stream to get a cup of molten lead right from the source... I could go for the idea, except for one other old problem: the water. The total water content of Venus is about one bucket of warm spit. If that's normal, then how could the proto-Moon impactor deliver world-wide oceans to the Earth? And if all the water here now outgassed from the Earth, why didn't as much water outgas from Venus? It should still be there, since it's almost impossible to transport water high enough in the Venusian atmosphere for it to escape... If a giant Venusian impactor was a 200 km. comet, it would certainly have enough CO2 for Venus' new atmosphere, BUT, again, where'd the water go??! On the other hand, if the impactor were a rocky body and pre-impact Venus had a substantial surface accumulation of carbonates... No problem. There a nice study by Zahnle and Sleep, Impacts and the Early Evolution of Life, which despite its title is really about modelling mega-impacts. They start with little mega-impacts like the ones that obliterate all life on Earth and work up to the really big ones, like Boils All The Oceans and Planets With An Atmosphere of Rock Vapor! They have a talent for thinking Big and Nasty. And they demonstrate that we still have to stretch our minds to understand impacts as big as, say, the one that produced the Imbrium basin on the Moon. The Earth should have suffered about 18 that size. The real problem is that Venus is a bitch! (Pardon my Pig Latin, although I suppose the ancient Romans would agree.) Everything we learn about it raises three more questions than it answers. We are at the important stage of enlarging our ignorance, something you have to do before you learn anything. Great stuff, ignorance. You are definitely right about one thing: the Earth is not normal. It's so wet; it has no stable surface, with all those strange tectonics going on all the time; it's accompanied by a double planet in virtually the same orbit; and it's infested by a jillion different kinds of molecular parasites: it is one weird place! Still, I'm enjoying my stay there... Sterling [EMAIL PROTECTED] wrote: Sterling, Interesting theory about Venus's atmosphere being blown off by a monster impactor. Here is my objection: Where did the 100 bar carbon dioxide atmosphere come from? Could one monster impactor blow off the existing atmosphere and yet at the same time deposit a new one? Seems a stretch. I suggest a different scenario. Mars is enriched in Argon 40 compared to earth for the same reason it is enriched in deuterium. The lighter elements are lost to space as a function of Mars's lesser gravity. Venus has a tremendous amount of CO2, Argon 36 neon, etc, because it atmosphere was not blown off into space by a giant impactor. On the contrary it was earth's atmosphere that was lost to space. Therefore using Earth's ratio of Ar 36/40 as a standard is misleading. What was the giant impactor responsible for the loss of earth's atmosphere. A good candidate is the impactor that created the moon. In any case, a young crystallization age of less than 500 million years would eliminate all sources, except Venus and Mars. Mike Fowler E.J wrote: Howard Wu wrote: Still the question was how would we recognize a venusian meteorite? Great question to ponder. The best way to identify a Venus Stone would be by the Argon isotope ratios. Argon-36 is the natural original isotope of Argon from the solar nebula. Argon-40 is formed by the radioactive decay of Potassium. It forms in the stone body of a planet and is released to the atmosphere by volcanic action, or out-gassing. On Earth, most of our Argon is isotope 40, thanks to our active little rockball, and there is very little natural Argon. The 40:36 isotope ratio is 296 to 1. On Mars, there is even less natural Argon. The 40:36 isotope ratio for Mars is 2750 +/- 500 to 1 (Is Mars more volcanic than the Earth? H.). So far, it all fits with those nice theories about volatiles and nebulas (which, you call tell by my tone, I distrust profoundly). Therefore, we would expect a ratio of 200:1 for Venus or maybe even 100:1, right? Here's where reality gets in its licks. First, there's 50 to 100 times more Argon and Neon in Venus' atmosphere than we would expect, huge amounts! Where in the H*** did that come from? Second, the 40:36 isotope ratio is 1 to 1, more or less. That is, they are present in roughly equal amounts. Say what? Well, maybe all the noble gasses are enriched? Nah, they're not. This
