[meteorite-list] Mercury data
From: Carl Agee <agee_at_meteoritecentral.com>
Date: Sun, 19 Jun 2011 10:16:35 -0600 Message-ID: <BANLkTinVEVipD-0fA-iEAFux=7QVBb-_5A_at_mail.gmail.com> Of course it's still early days on understanding the Mercury data coming back from Messenger, but I think there are a few simple things that can be said about the two geochemical graphs that were part of the press release. The major element graph of Al/Si versus Mg/Si clearly shows that the measured Mercurian surface is similar to basaltic and mantle rocks from the Earth. They plot along the Earth array and look to be a bit more olivine-rich than mid-ocean ridge basalts, but not as olivinerich as mantle peridotites, perhaps more like Archean Earth komatiites. The measured Mercurian surface is NOT delpleted in aluminum, like Martian basalts or Angrites. Also, Messenger is clearly not measuring rocks like the lunar anorthositic highlands. The major element that is still missing from this puzzle is iron. The data do not say anything about the FeO content of the Mercurian surface -- this is a pretty big deal, and until that is known it will difficult to know exactly what we are looking at -- let alone if there is a match for any known meteorite type. The potassium/thorium plot shows that Mercury is a lot like the other terrestrial planets in terms of volatile element content. It seems to be closest to the K/Th of Mars which is quite surprising, since Mars is thought to be the most volatile rich of the rocky planets. This runs counter to the idea that the inner solar system is chemically zoned with volatile elements concentrated out at Mars and lower in towards the Sun. But who knows? Maybe Mercury formed farther from the Sun and migrated inwards. There was a brief mention of substantial amounts of sulfur, but no data in the multimedia press release, so it would be interesting to know what they mean by "substantial amounts". Also, why do they think it is in the form of sulfide and not sulfate? See how important these missions of planetary exploration are and how fragmentary our understanding is? Just my opinion.... 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: agee at unm.edu http://epswww.unm.edu/iom/pers/agee.htmlReceived on Sun 19 Jun 2011 12:16:35 PM PDT |
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