[meteorite-list] NWA5400
Since this tracks on the terestial O2 line, can this be concidered a planetary meteorite, along with the Lunars, Martians, as well as Asteroid 4 vesta? Would these be the only 4 planitaries so far or has maybe Mecrury checked in with a sample of it's own? Pete IMCA 1733 __ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] NWA5400
Hi Pete, Aubrites and enstatite chondrites also plot on the oxygen isotope terrestrial fractionation line (TFL) and up to now they are not proven to be from planets. So being on the TFL doesn't make the meteorite planetary. But I guess it depends on your definition of planetaries, I would only put lunars and martians in that category, but not HEDs. Last time I checked, 4 Vesta the hypothesized HED parent body, was still an asteroid, not a planet. I see no reason to consider NWA 5400 planetary. On the other hand, if someone did an age-date on it, and it came up with a crystallization age much more recent than ~4.5 B.Y., then things would get interesting. This is because asteroidal achondrites have ages ~4.5 B.Y., whereas planets tend to have younger basalts. Likewise, the search for meteorites from Mercury or Venus should include igneous crystallization ages as part of the proof. Carl Agee Carl B. Agee Director and Curator, Institute of Meteoritics Professor, Earth and Planetary Sciences MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 Tel: (505) 750-7172 Fax: (505) 277-3577 Email: a...@unm.edu http://meteorite.unm.edu/people/carl_agee/ On Mon, Mar 11, 2013 at 2:20 AM, pshu...@messengersfromthecosmos.com wrote: Since this tracks on the terestial O2 line, can this be concidered a planetary meteorite, along with the Lunars, Martians, as well as Asteroid 4 vesta? Would these be the only 4 planitaries so far or has maybe Mecrury checked in with a sample of it's own? Pete IMCA 1733 __ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list -- -- Carl B. Agee Director and Curator, Institute of Meteoritics Professor, Earth and Planetary Sciences MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 Tel: (505) 750-7172 Fax: (505) 277-3577 Email: a...@unm.edu http://meteorite.unm.edu/people/carl_agee/ __ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] NWA5400
Dear Professor Agee, The IAU's decision to go all rogue on the definition of a planet, dwarf-planet, minor-planet, [iamnotaplanet, iamtooaplanet, someplanetnamedstan] doesn't leave me with a warm and fuzzy about calling Earth a planet. Cleared our orbit - I'm not even certain that's necessarily the case... But then, having spent my formative years haunting Lowell Observatory, I've got a dog in that fight and I'm pretty compromised intellectually/emotionally on the whole topic. I agree that today the IAU defines 4Vesta as a minor planet the same as any other asteroid, though it's larger and with more of a cleared orbit than Makemake or probably Haumea, both dwarf planets per the IAU, and not far behind Ceres. I'm not at all confident the IAU won't change their mind tomorrow** and turn it into a dwarf planet with the same total lack of regard and status as Pluto received. --- Jodie ** 4Vesta appears to have far more hydrostatic equilibrium than dwarf-planet Haumea, and it appears to have cleared its neighborhood more than any of the other Small Solar System Bodies excepting Ceres, per Resolution 5A. Resolution 5B would have cleared a lot of that up, but 5A was passed and 5B shot down, go figger, and now we need to worry about trans-Neptunian dwarf planets that aren't planets at all but bear the name 'planet' ;-) Monday, March 11, 2013, 7:41:12 AM, you wrote: Hi Pete, Aubrites and enstatite chondrites also plot on the oxygen isotope terrestrial fractionation line (TFL) and up to now they are not proven to be from planets. So being on the TFL doesn't make the meteorite planetary. But I guess it depends on your definition of planetaries, I would only put lunars and martians in that category, but not HEDs. Last time I checked, 4 Vesta the hypothesized HED parent body, was still an asteroid, not a planet. I see no reason to consider NWA 5400 planetary. On the other hand, if someone did an age-date on it, and it came up with a crystallization age much more recent than ~4.5 B.Y., then things would get interesting. This is because asteroidal achondrites have ages ~4.5 B.Y., whereas planets tend to have younger basalts. Likewise, the search for meteorites from Mercury or Venus should include igneous crystallization ages as part of the proof. Carl Agee Carl B. Agee Director and Curator, Institute of Meteoritics Professor, Earth and Planetary Sciences MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 Tel: (505) 750-7172 Fax: (505) 277-3577 Email: a...@unm.edu http://meteorite.unm.edu/people/carl_agee/ On Mon, Mar 11, 2013 at 2:20 AM, pshu...@messengersfromthecosmos.com wrote: Since this tracks on the terestial O2 line, can this be concidered a planetary meteorite, along with the Lunars, Martians, as well as Asteroid 4 vesta? Would these be the only 4 planitaries so far or has maybe Mecrury checked in with a sample of it's own? Pete IMCA 1733 __ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list -- -- Best regards, Jodiemailto:spacero...@spaceballoon.org __ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] NWA5400
Hi Jodie, My bias is from a planetary differentiation perspective. The only known meteorites to sample solar system bodies with long-lived (1 BY) igneous activity are lunars and martians. The HEDs might be considered borderline planetaries, since some cumulate eucrites have slightly younger ages than 4.5 BY, but that may be from metamorphism rather than primary igneous activity. So, given my bias, I see all the ancient achondrites as coming from asteroids and the only planetaries (yet known) are lunar and martian. You see, my bias is such that I consider the Moon to be in the same category as terrestrial planets, and that it just happens to orbit the Earth. This is probably not how astronomers see the the solar system, but just fine for an igneous petrologist! Best, Carl -- Carl B. Agee Director and Curator, Institute of Meteoritics Professor, Earth and Planetary Sciences MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 Tel: (505) 750-7172 Fax: (505) 277-3577 Email: a...@unm.edu http://meteorite.unm.edu/people/carl_agee/ On Mon, Mar 11, 2013 at 12:15 PM, Jodie Reynolds spacero...@spaceballoon.org wrote: Dear Professor Agee, The IAU's decision to go all rogue on the definition of a planet, dwarf-planet, minor-planet, [iamnotaplanet, iamtooaplanet, someplanetnamedstan] doesn't leave me with a warm and fuzzy about calling Earth a planet. Cleared our orbit - I'm not even certain that's necessarily the case... But then, having spent my formative years haunting Lowell Observatory, I've got a dog in that fight and I'm pretty compromised intellectually/emotionally on the whole topic. I agree that today the IAU defines 4Vesta as a minor planet the same as any other asteroid, though it's larger and with more of a cleared orbit than Makemake or probably Haumea, both dwarf planets per the IAU, and not far behind Ceres. I'm not at all confident the IAU won't change their mind tomorrow** and turn it into a dwarf planet with the same total lack of regard and status as Pluto received. --- Jodie ** 4Vesta appears to have far more hydrostatic equilibrium than dwarf-planet Haumea, and it appears to have cleared its neighborhood more than any of the other Small Solar System Bodies excepting Ceres, per Resolution 5A. Resolution 5B would have cleared a lot of that up, but 5A was passed and 5B shot down, go figger, and now we need to worry about trans-Neptunian dwarf planets that aren't planets at all but bear the name 'planet' ;-) Monday, March 11, 2013, 7:41:12 AM, you wrote: Hi Pete, Aubrites and enstatite chondrites also plot on the oxygen isotope terrestrial fractionation line (TFL) and up to now they are not proven to be from planets. So being on the TFL doesn't make the meteorite planetary. But I guess it depends on your definition of planetaries, I would only put lunars and martians in that category, but not HEDs. Last time I checked, 4 Vesta the hypothesized HED parent body, was still an asteroid, not a planet. I see no reason to consider NWA 5400 planetary. On the other hand, if someone did an age-date on it, and it came up with a crystallization age much more recent than ~4.5 B.Y., then things would get interesting. This is because asteroidal achondrites have ages ~4.5 B.Y., whereas planets tend to have younger basalts. Likewise, the search for meteorites from Mercury or Venus should include igneous crystallization ages as part of the proof. Carl Agee Carl B. Agee Director and Curator, Institute of Meteoritics Professor, Earth and Planetary Sciences MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 Tel: (505) 750-7172 Fax: (505) 277-3577 Email: a...@unm.edu http://meteorite.unm.edu/people/carl_agee/ On Mon, Mar 11, 2013 at 2:20 AM, pshu...@messengersfromthecosmos.com wrote: Since this tracks on the terestial O2 line, can this be concidered a planetary meteorite, along with the Lunars, Martians, as well as Asteroid 4 vesta? Would these be the only 4 planitaries so far or has maybe Mecrury checked in with a sample of it's own? Pete IMCA 1733 __ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list -- -- Best regards, Jodiemailto:spacero...@spaceballoon.org __ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] NWA5400 redux - a long explanation
Hi David, Carl and List, Thanks for the detailed explanation David. :) I recall reading something about catastrophic events that can reset the CRE of some materials. Maybe I am not remembering correctly. Is it possible that a cataclysmic event could shock/alter a material to such a degree that it would scramble the isotopes contained within? I also seem to recall something about the radioactive isotopes of Aluminum (?) somehow figuring into this reset equation. Can someone clear me up on this? What I am getting at, in relation to NWA 5400/Thea impact theories is - the event in question was catastrophic on every level. Would this complicate the analysis of determining any age or origin for this material? Personally, I find any meteorite that plots along the terrestrial fractionation line to be interesting, in that it stands apart from most other types of meteorites which do not. So NWA 5400 is interesting, regardless of what it is or is not paired with. So, if NWA 5400 is a brachinite, or is related to brachinites, then it visually looks quite different from the majority of brachinites I have seen. Going strictly by aesthetics, 5400 seems to have more in common with enstatite meteorites than brachinites. Is it just me? 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 --- On 9/28/10, drv...@sas.upenn.edu drv...@sas.upenn.edu wrote: Carl: I am glad that I provoked thought - that is in my mandate as an educator...;) I will try to answer your questions, albeit perhaps not in order, and I hope I can explain. First, you ask about Mbarak's box of rocks, aren't they likely paired? Well, it is very unlikely that two different brachinites fell in the same spot. Not impossible, but very unlikely. Therefore, it seems likely that the rocks are from the same fall if found in the same area. Second, you have several questions about O isotopes. In the case of NWA5400 pairings, it is important because all agree that it is a brachinite (more on this below); what makes it unusual is that is has different O isotopes than other brachinites, so any rocks that have similar O isotopes are likely from the same meteoroid. Oxygen isotopes haven't really taken over the pairing question; as has already been noted, many different parameters must converge before two rocks can be paired. What's up with the O isotope thing anyway? Oxygen has three 'isotopes' - it has three different weights, based on the number of neutrons in its nucleus. The weights, relative to hydrogen, are 16, 16 and 18. Theoretically, as oxygen is formed in the fusion reactions of the Sun and expelled, or trapped from molecules drifting in interstellar space, these three isotopes begin to sort out in the solar wind. The gravitational attraction of the lighter isotope, 16O, is, naturally, less than the others. Thus, the solar wind can more easily push the lighter isotope farther out into space. Consequently, there is a gradient of increasing amounts of 16O relative to 18O as you go farther out. (same logic appllies to 17O, of course). Since the sun continues to form oxygen, the system is continually replenished, and is thus arguably at a steady state (or there would be the complication that we don't know the gradient 4.5 billion years ago). This theoretical concept is borne out by spectrographic measurements in space, so it seems to work. Within these gradients, planets formed. When, for instance, magnesium reacts with silicon and oxygen to form magnesium silicate (e.g. enstatite), it clearly would condense with the distribution of oxygen isotopes where it condensed. This is the basis for the idea that oxygen isotopes record how far away from the Sun the matter condensed. Naturally, there are complications, which I may gert back to before I finish here. Almost startlingly, when the first bunch of meteorites were analyzed, they showed a pattern consistent with this expectation. THus, oxygen isotopes are used to *infer* whereabouts the sample originated, at least within a few million miles or so. Now, as to NWA5400; maybe only two abstracts have been publshed. Keep in mind that it can take a while for things to get published, and it can take quite a while to complete these analyses and get them right. But, I would like to say, the two abstracts published say quite a lot, and reflect a great deal of analyses already performed. Tony Irvings group has, in my opinion produced as musch useful information as most of what gets published in the magazine Science. The problem is that
[meteorite-list] Nwa5400 rdux - oops!
To all: In response to Greg C. - yes you can repost it, and I take responsbility for any errors or confusions arising. I would like to correct an error I made writing this late last night after a tiring day rebuilding parts of my mass spectrometer: The Sun is not currently making oxygen; there is a sentence that effectively states it does below - I think I crossed two sentences in my head as I was writing. So, again, the Sun is not the source of the oxygen, or for that matter, any of the 'heavier' elements - yet. Once it depletes enough hydrogen, it will swich to Helium fusion, and begin synthesizing carbon. Conceivably, some of this does occur within the core, but that would not escape yet. The source of the 'heavier' elements is cosmic debris, likely from a nearby supernova explosion that has enriched our star in these elements relative to others that have a similar age and type. [also, a minor typo - the weights of O isotopes are 16,17 and 18, not 16,16,and 18 as noted below- but then, I'm sure you'all figured that one out for yourselves...;) - must stop writing things late at night...] So, the sentence should read: Theoretically, as oxygen is formed in the fusion reactions of stars and expelled when they die, or trapped from molecules drifting in interstellar space, these three isotopes begin to sort out in the solar wind Later, another sentence should read: Since the sun continues to expel oxygen, the system is continually replenished, and is thus arguably at a steady state (or there would be the complication that we don't know the gradient 4.5 billion years ago) And add the following to clarify: The source of this oxygen is largely particles that fall into the Sun's photosphere due to gravitational attraction; molecules such as enstatite are blown apart in the plasma, back into their consituent atoms. In the aubrite discussion: Conventional thinking on their formation is that they formed under reducing conditions, i.e. a lack of oxygen. I was trying to invert this explanation and got it tangled up with solar oxygen, completely wrong. During this period n the formation, the area was very rich in hydrogen and the protosolar disk was forming and 'igniting'. In this area, the amount of oxygen available, relative to heavier elements such as silicon and magnesium, was too low to form much beyond enstatite (this is past, or near the end of, carbonaceous chondrite formation). A better way of looking at this, is that the materials that condensed into larger bodies also had, say, a lot of iron oxides as well as enstatite. As the planetoid formed, the heat allowed transfer of oxygen from metal iron.nickel oxides to the enstatite, forming olivine, whereas the now-reduced metals suck into the core - same as you would make iron today from e.g. hematite, leaving behind an oxygen-enriched silicate slag. I think, trying to make the story seem simple when it is really far more complicated that I put it, I went astray. There, I think I got it right this time, to the best of my current understanding. Sorry about any confusion or inconvenience this caused - next time, I promise to better proofread what I write... I also missed the reference that says CRE has been done on the sample; thanks to Sterling and Richard for explaining the reason for the apparent discrepancy, as I was about to do just this, and therefore they saved me the trouble, so that I can continue to do battle with the MS... DRVann | -Original Message- | From: Greg Catterton [mailto:star_wars_collec...@yahoo.com] | Sent: Wednesday, September 29, 2010 10:44 AM | To: drv...@sas.upenn.edu | Subject: Re: [meteorite-list] NWA5400 redux - a long explanation | | | Awesome info! do you mind if I repost some of this? | | Greg Catterton | www.wanderingstarmeteorites.com | IMCA member 4682 | On Ebay: http://stores.shop.ebay.com/wanderingstarmeteorites | On Facebook: http://www.facebook.com/WanderingStarMeteorites | | | --- On Tue, 9/28/10, drv...@sas.upenn.edu | drv...@sas.upenn.edu wrote: | | From: drv...@sas.upenn.edu drv...@sas.upenn.edu | Subject: [meteorite-list] NWA5400 redux - a long explanation | To: cdtuc...@cox.net | Cc: meteorite-list@meteoritecentral.com | Date: Tuesday, September 28, 2010, 11:57 PM | Carl: | I am glad that I provoked thought - that is in my mandate | as an educator...;) | | I will try to answer your questions, albeit perhaps not in | order, and | I hope I can explain. | | First, you ask about Mbarak's box of rocks, aren't they | likely paired? | Well, it is very unlikely that two different brachinites fell in the | same spot. Not | impossible, but very unlikely. Therefore, it seems likely | that the rocks are | from the same fall if found in the same area. | | Second, you have several questions about O isotopes. In the case of | NWA5400 pairings, it is important because all agree that it is a | brachinite (more on | this below); what makes it unusual is that is has
[meteorite-list] NWA5400 redux - a long explanation
Carl: I am glad that I provoked thought - that is in my mandate as an educator...;) I will try to answer your questions, albeit perhaps not in order, and I hope I can explain. First, you ask about Mbarak's box of rocks, aren't they likely paired? Well, it is very unlikely that two different brachinites fell in the same spot. Not impossible, but very unlikely. Therefore, it seems likely that the rocks are from the same fall if found in the same area. Second, you have several questions about O isotopes. In the case of NWA5400 pairings, it is important because all agree that it is a brachinite (more on this below); what makes it unusual is that is has different O isotopes than other brachinites, so any rocks that have similar O isotopes are likely from the same meteoroid. Oxygen isotopes haven't really taken over the pairing question; as has already been noted, many different parameters must converge before two rocks can be paired. What's up with the O isotope thing anyway? Oxygen has three 'isotopes' - it has three different weights, based on the number of neutrons in its nucleus. The weights, relative to hydrogen, are 16, 16 and 18. Theoretically, as oxygen is formed in the fusion reactions of the Sun and expelled, or trapped from molecules drifting in interstellar space, these three isotopes begin to sort out in the solar wind. The gravitational attraction of the lighter isotope, 16O, is, naturally, less than the others. Thus, the solar wind can more easily push the lighter isotope farther out into space. Consequently, there is a gradient of increasing amounts of 16O relative to 18O as you go farther out. (same logic appllies to 17O, of course). Since the sun continues to form oxygen, the system is continually replenished, and is thus arguably at a steady state (or there would be the complication that we don't know the gradient 4.5 billion years ago). This theoretical concept is borne out by spectrographic measurements in space, so it seems to work. Within these gradients, planets formed. When, for instance, magnesium reacts with silicon and oxygen to form magnesium silicate (e.g. enstatite), it clearly would condense with the distribution of oxygen isotopes where it condensed. This is the basis for the idea that oxygen isotopes record how far away from the Sun the matter condensed. Naturally, there are complications, which I may gert back to before I finish here. Almost startlingly, when the first bunch of meteorites were analyzed, they showed a pattern consistent with this expectation. THus, oxygen isotopes are used to *infer* whereabouts the sample originated, at least within a few million miles or so. Now, as to NWA5400; maybe only two abstracts have been publshed. Keep in mind that it can take a while for things to get published, and it can take quite a while to complete these analyses and get them right. But, I would like to say, the two abstracts published say quite a lot, and reflect a great deal of analyses already performed. Tony Irvings group has, in my opinion produced as musch useful information as most of what gets published in the magazine Science. The problem is that the scientific community does not know enough about the genesis of the Solar system to do much more than speculate about the meaning of the results. But what results they are: NWA 5400 is a Brachinite. What this means, is that it consists primarily of olivine (peridot) and is classified as an ultramafic rock - one high in Magnesium and iron and low in silicates (compared to crustal rocks of Earth). It is dense. In geology, one might call this rock a dunite or dunitic wehrlite; we find rocks like this on Earth (I have a few on my desk), and the compostion resembles the upper mantle of the Earth. The mineralogy of the rock isn't actually particularly rare. Because the isotope resemble Earth's, it has been suggested that NWA5400 is a remnant of the putative Earth-Theia impact. For a number of reasons, Theia probably formed near Earth's orbit, thus had an oxygen isotopic distribution similar to Earth's. The collision was more than powerful enough to exhume portions of Earth's mantle, particularly since, at this time, Earth wasn't yet exactly solid in the way we perceive it today. The metal content isn't really an issue. There isn't actually very much, and most resides in sulfides. It is also quite conceivable that, this early in Earth's planetogenesis, substantial amounts (by this I mean, say, 2-3%) of iron and nickel had not yet migrated to the core. Thus, a piece of the upper mantle knocked into space 4.5 billion yrs ago might have more metal than one might expect based on today's observations of the Earth. Do keep in mind, though, that we do fiond metal-rich rocks on Earth, even at the surface; the Plato Putorano basalt comes to mind. What is clear is that the rock had formed on a body big enough to differentiate. BTW, the there is an age on NWA5400; age of formation is consistent with Theia time frame. CRE ages are
