[meteorite-list] ureilite / venus connection
From: Joseph Hum <jkarlhum_at_meteoritecentral.com>
Date: Thu Apr 22 09:43:29 2004 Message-ID: <4120017082828620_at_earthlink.net> ------=_NextPart_84815C5ABAF209EF376268C8 Content-type: text/plain; charset=US-ASCII Hi Almitt, thanks for the imput of that author! i would assert though, even going with that limited analysis there is little in those statements that perclude a Venusian origin 100km + asteroid, that is a rather large asteroid that we would probably know about, unless it was fragmented futher by other collisions the same sort of vulcanism and phenomenon could occur on Venus there are no known asteroids that i'm aware of with similiar spectra there is not only carbon/ graphite, but other allotropes/phases, including diamonds found in these rocks i would like to see further isotopic analyses done esp. of the primative Ar/Ne isotope ratios, etc. Regards, Karl ----- Original Message ----- From: almitt To: jkarlhum_at_earthlink.net Cc: Meteorite-list_at_meteoritecentral.com Sent: 7/7/01 4:00:22 PM Subject: Re: [meteorite-list] ureilite / venus connection Joseph and all, Here is what Harry Y. McSween has to say about these types of meteorites in his most excellent book Meteorites and Their Parent Planets. Ureilite were derived from a body with a particularly complex history. The interior was partially melted and basaltic magma was extracted. The ureilite residue was then held at a temperatures of at least 1,250 deg. C for some time, causing it to recrystallize. The reduction of iron seen in the rims of sensitive silicate grains suggests reaction with graphite, a reaction that is extremely sensitive to pressure. Estimates of the pressure needed to account for the compositions of reduced silicates correspond to depths of approximately 100 km, possibly a minimum size for the ureilite parent asteroid. Various workers have called on explosive volcanism, shock heating by impact, or the impact of a carbonaceous asteroid into an already molten body to explain the curious characteristics of these meteorites. Because of their high carbon content, ureilites are very dark, with albedos of only approximately 7%. The spectra of low-albedo members for the S(I) subtype are dominated by olivine and S(II) asteroids additionally contain a small amount of calcium rich pyroxene. Either of these sub-classes might correspond to the mineralogy of brachinites. He goes on to say that the S type asteroids are interpreted to represent potentially a range of meteorite types from ordinary to primitive achondrites from a small degree of melting. The diversity in these S type asteroids is probably a direct result of the igneous processes that many of the these asteroids have experienced. To me this suggests an asteroid parent body rather than a planetary type body. --AL Joseph Hum wrote: i would like to hear some feedback concerning the possibleconnection between the exotic meteorites- ureilites- and a possible venusian origininstead of just dwelling on whether tektites have a lunar origin or notanyway, what about UREILITES? Regards, J.K. Hum --- Joseph Hum --- Joseph Hum --- jkarlhum_at_earthlink.net --- EarthLink: It's your Internet. ------=_NextPart_84815C5ABAF209EF376268C8 Content-Type: text/html; charset=US-ASCII <HTML><HEAD> <META content="text/html; charset=windows-1251" http-equiv=Content-Type> <META content="MSHTML 5.00.3211.1700" name=GENERATOR></HEAD> <BODY> <DIV>Hi Almitt,</DIV> <DIV> </DIV> <DIV>thanks for the imput of that author!</DIV> <DIV>i would assert though, even going with that limited analysis</DIV> <DIV>there is little in those statements that perclude a Venusian origin</DIV> <DIV>100km + asteroid, that is a rather large asteroid that we would probably</DIV> <DIV>know about, unless it was fragmented futher by other collisions</DIV> <DIV>the same sort of vulcanism and phenomenon could occur on Venus</DIV> <DIV>there are no known asteroids that i'm aware of with similiar spectra</DIV> <DIV>there is not only carbon/ graphite, but other allotropes/phases, </DIV> <DIV>including diamonds found in these rocks</DIV> <DIV>i would like to see further isotopic analyses done</DIV> <DIV>esp. of the primative Ar/Ne isotope ratios, etc. </DIV> <DIV> </DIV> <DIV>Regards,</DIV> <DIV>Karl</DIV> <DIV> </DIV> <DIV> </DIV> <DIV> </DIV> <DIV> </DIV> <DIV> </DIV> <BLOCKQUOTE style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px"> <DIV style="FONT: 10pt Arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B> <A href="mailto:almitt_at_kconline.com" title=almitt@kconline.com>almitt</A> </DIV> <DIV style="FONT: 10pt arial"><B>To: </B><A href="mailto:almitt_at_kconline.com" title=almitt@kconline.com>jkarlhum@earthlink.net</A> <DIV style="FONT: 10pt arial"><B>Cc: </B><A href="mailto:almitt_at_kconline.com" title=almitt@kconline.com>Meteorite-list@meteoritecentral.com</A></DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> 7/7/01 4:00:22 PM </DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [meteorite-list] ureilite / venus connection</DIV> <DIV><BR></DIV><FONT size=2> <P> <DIV>Joseph and all,</DIV> <DIV> </DIV> <DIV>Here is what Harry Y. McSween has to say about these types of meteorites in his most</DIV> <DIV>excellent book Meteorites and Their Parent Planets.</DIV> <DIV> </DIV> <DIV>Ureilite were derived from a body with a particularly complex history. The interior</DIV> <DIV>was partially melted and basaltic magma was extracted. The ureilite residue was then</DIV> <DIV>held at a temperatures of at least 1,250 deg. C for some time, causing it to</DIV> <DIV>recrystallize. The reduction of iron seen in the rims of sensitive silicate grains</DIV> <DIV>suggests reaction with graphite, a reaction that is extremely sensitive to pressure.</DIV> <DIV>Estimates of the pressure needed to account for the compositions of reduced silicates</DIV> <DIV>correspond to depths of approximately 100 km, possibly a minimum size for the ureilite</DIV> <DIV>parent asteroid. Various workers have called on explosive volcanism, shock heating by</DIV> <DIV>impact, or the impact of a carbonaceous asteroid into an already molten body to</DIV> <DIV>explain the curious characteristics of these meteorites. Because of their high carbon</DIV> <DIV>content, ureilites are very dark, with albedos of only approximately 7%. The spectra</DIV> <DIV>of low-albedo members for the S(I) subtype are dominated by olivine and S(II)</DIV> <DIV>asteroids additionally contain a small amount of calcium rich pyroxene. Either of</DIV> <DIV>these sub-classes might correspond to the mineralogy of brachinites.</DIV> <DIV> </DIV> <DIV>He goes on to say that the S type asteroids are interpreted to represent potentially a</DIV> <DIV>range of meteorite types from ordinary to primitive achondrites from a small degree of</DIV> <DIV>melting. The diversity in these S type asteroids is probably a direct result of the</DIV> <DIV>igneous processes that many of the these asteroids have experienced.</DIV> <DIV> </DIV> <DIV>To me this suggests an asteroid parent body rather than a planetary type body.</DIV> <DIV> </DIV> <DIV>--AL</DIV> <DIV> </DIV> <DIV>Joseph Hum wrote:</DIV> <DIV> </DIV> <DIV>> i would like to hear some feedback concerning the possibleconnection between the</DIV> <DIV>> exotic meteorites- ureilites- and a possible venusian origininstead of just</DIV> <DIV>> dwelling on whether tektites have a lunar origin or notanyway, what about</DIV> <DIV>> UREILITES? Regards, J.K. Hum --- Joseph Hum</DIV> <DIV> </DIV> <P></P></FONT> <P></P></DIV></BLOCKQUOTE> <DIV> </DIV> <DIV>--- Joseph Hum</DIV> <DIV>--- <A href="mailto:jkarlhum_at_earthlink.net">jkarlhum@earthlink.net</A></DIV> <DIV>--- EarthLink: It's your Internet.</DIV> <DIV> </DIV></BODY></HTML> ------=_NextPart_84815C5ABAF209EF376268C8-- Received on Sat 07 Jul 2001 10:08:28 PM PDT |
 StumbleUpon del.icio.us reddit Yahoo MyWeb
|