[meteorite-list] Serious question?

From: Philip R. Burns <pib_at_meteoritecentral.com>
Date: Thu Apr 22 10:29:56 2004
Message-ID: <5.2.0.9.2.20030916184012.01fd2d90_at_pibburns.com>

At 11:00 PM 9/16/2003 +0000, you wrote:

>The concept of a red planet as the result of meteorite bombardment is absurd.

Maybe not, if you have the right kind of planet, namely one with an
atmosphere and appropriate oxidizing compounds. Albert Yen and colleagues
wrote a paper about this a bit in _Science_ a few years back. I don't
have the paper at hand, but I think it was sometime around September
2000. Yen suggested a "super-oxide" process to explain present day soil
rusting on Mars with ultraviolet light the catalyst. Since this process is
very slow, even by geological time scales, many planetologists still
believe most of the red color probably dates back to a time when Mars was
wetter.

More recently (see http://www.newscientist.com/news/news.jsp?id=ns99994120)
Yen has proposed that meteorites form the main source for the red soil. He
exposed metallic iron in a specially created environment matching the
atmospheric composition and temperature of Mars. Yen found that red oxides
began to form within a week -- in other words, orders of magnitude more
quickly than previously assumed. So there may be something to this idea
after all.

Properly equipped Martian landers will probably be able to shed more light
on this subject. If Yen is right, the Martian soil should show an
overabundance of nickel, indicating a probable meteoric origin. The Mars
Pathfinder mission has already suggested that the soil contains more
magnesium and iron than rocks on the surface.

>As you and others have pointed out, water and oxygen are not necessary for
>oxidization. We have plenty of areas on earth that are pretty bleak but we
>all know about geological time as opposed to our own inabilaty to comprehend
>it in a real sense and the amazing affects of weather and all the rest. My
>only point was that given the fact that iron can turn into red stuff as the
>result of a variety of reactions, why isn't the earth's moon very very red?

The type of vapor deposition process which weathers the lunar surface may
initially lead to reddening, but later leads to darkening. See the article
by Bruce Hapke in the Journal of Geophysical Research, vol. 106, pp.
10039-10073.

There is also evidence of reddening on some smaller airless bodies as a
result of space weathering. This has important consequences for
determining the parent bodies of meteorites.

>Mars has a violent atmosphere that should mix all that "meteoric" debris up?
>This is only a question as a student might ask. I'm not trying to engage in a
>debate.

Actually such atmospheric activity supports Yen's idea. The soil on Mars
is constantly being mixed up, and so the darkening characteristic of space
weathering on airless bodies doesn't take place.


-- Philip R. "Pib" Burns
    pib_at_pibburns.com
    http://www.pibburns.com/
Received on Tue 16 Sep 2003 08:47:22 PM PDT