[meteorite-list] Nwa 7034

From: Carl Agee <agee_at_meteoritecentral.com>
Date: Sun, 27 Jan 2013 09:20:21 -0700
Message-ID: <CADYrzhqnfowqmDVtxYS8-eakc9pGxqde1rZY9=gOpgRHWg0oXg_at_mail.gmail.com>

Hi Jeff,

Of course the comparison between chondrite groups and martian types is
not perfect. The different martian types are not from different parent
bodies, but we still don't know where they come from on Mars, and
won't for a long time, not until we know the geology of Mars better.
So for a large body like a planet, and given our fragmentary knowledge
of Mars, different regions are more or less equivalent to different
parent bodies. Describing martians with generic lithologic names that
were developed for Earth geology is useful, but for example we don't
hesitate to use the term mid-ocean ridge basalts (MORB) for Earth's
most abundant rock type, which will never be found on Mars. The same
is true for Mars because of a different planetary evolution. We are
already doing this based on rover data, the term "Gusev basalt" is one
example. SNC's plus ALH 84001 and NWA 7034 are, each type, glimpses of
diversity of Mars' unique geology.

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://meteorite.unm.edu/people/carl_agee/
---------- Forwarded message ----------
From: Jeff Grossman <jngrossman at gmail.com>
To: <meteorite-list at meteoritecentral.com>
Cc:
Date: Sun, 27 Jan 2013 00:06:22 -0500
Subject: Re: [meteorite-list] Nwa 7034
There are two reasons why we can't get rid of carbonaceous chondrite
group names.  First, unlike Martian meteorites, we don't know where C
chondrites came from.  We can't point to a single asteroid as the
source for any of them, let alone all of them.  So the group names are
still serving their basic purpose of ordering the chaos.  Second, the
only language we have to describe the rocks known as chondrites is by
their group names.  They can't be described with standard rock
nomenclature. So this is not a fair comparison.
I didn't say Martian meteorite names were not useful.  I said they
were archaic, historical artifacts.
Jeff
On 1/26/2013 11:38 PM, Carl Agee wrote:
    Hi Jeff and all you Nomenclature Enthusiasts out there:
    I think the martian meteorite names do serve a useful purpose, they
    are a sort of short-hand, so that you don?t have to be an igneous
    petrologist to know that one type of martian is different from
    another.  So when we say a martian meteorite is a ?NWA7034-ite?, or
    ?blackbeauty-ite?,  or a ?saharite? or whatever name you want to pick,
    we are implicitly talking about a breccia, that is water-rich, alkali
    basalt, with higher-than-SNC oxygen isotope values, ~ 2 byo, etc.  For
    example, like it or not, when we say ?Allan Hills? the first thing
    comes that comes to mind is ALH 84001.  When you say orthopyroxenite
    maybe not so much. If it?s such a great idea to do away with martian
    types, why don?t we go ahead and do away with all the carbonaceous
    chondrite groups  like CI, CM, CV, etc. and just call them all
    carbonaceous chondrites, that of course have a wide range of
    compositions, textures, mineralogies etc.? Meteoritics isn?t the only
    science that has colorful nomenclature. Mineralogists still like to
    name new minerals after famous mineralogists, instead of just naming
    them by their chemical composition or crystal structure.
    Carl Agee

Received on Sun 27 Jan 2013 11:20:21 AM PST