[meteorite-list] Meteorites on Mars

From: Sterling K. Webb <kelly_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:00 2004
Message-ID: <3FFCF707.8417D746_at_bhil.com>

     Hi,

         In the largest scale computer simulation (by Bret Gladman) of
     rocks knocked off planets, the following tables show what
     percentages of chunks make it to what planets:

     Ejecta From Earth/Moon
     Mercury 0%
     Venus 15%
     Earth/Moon 50%
     Mars 0.1%
     Escapes 34.9%

     Ejecta From Mars
     Mercury 0%
     Venus 4%
     Earth/Moon 5%
     Mars 3%
     Escapes 88%

         You can see that the Earth/Moon system is very good at
     sweeping up its own debris (50%) while Mars only re-captures 3% of
     its ejecta. The Earth (and Venus, too) get more chunks of Mars
     than Mars does!
         That means that, oddly enough, of the two places in the
     universe that look exactly like the Mars Rover images, namely,
     Mars and Arizona, you'd be better off looking for Mars meteorites
     in Arizona than on Mars itself.
         On the other hand, Mars gets only a tiny fraction of the Earth
     rocks (one in a thousand). The Earth/Moon gets 50 times more Mars
     rocks than Mars gets Earth (and Moon) rocks. So the likelihood of
     finding a "terrestrial" meteorite on Mars is small indeed!
         If the Earth has 25 Mars rocks (discovered), a similarly
     intensive search of Earth meteorites on Mars would have been
     unlikely to have found even one. Of course, meteorites may persist
     on the Martian surface for much longer than they could survive on
     a terrestrial surface and in that case the incidence of Earth
     meteorites would be multiplied by a time factor.
         If what we're looking at in the Rover images is a surface
     unchanged for 3 billion years (which some would say it is), there
     would be 60,000 times more Earth meteorites on it than if it
     degraded meteorites as fast as the Earth does! But that's still
     only one Earth (or Moon) meteorite for every 500 square miles of
     Mars (scaled to the 25 Martian rocks found on Earth).
         All of this assumes equal "landability" for meteorites on Mars
     and the Earth, which as has been pointed out is not likely to be
     the case.
         Packing for Mars? It's probably a waste of time. Just put that
     Universal Achondrite Detector back in the closet, hang up your
     space suit, drain the fuel from your lander, and point the SUV for
     Arizona instead.


     Sterling K. Webb
     ------------------------------------
     Ron Baalke wrote:

>1. Mars' thinner atmosphere means more
>meteorites survive the fall though it
>than on Earth.

          There are a number of factors to consider. Mars is
          smaller
          than Earth, so has less gravity to pull in meteoroids.
          However, Mars is closer to the asteroid belt, so is more

          likely to encounter meteoroids than Earth. The thinner
          atmosphere means
          it is more likely a meteorite will reach the surface,
          but it
          also means it is more likely to impact at hypervelocity
          speeds, and hypervelocity impacts tends to totally
          vaporize meteorites.

          Ron Baalke
Received on Thu 08 Jan 2004 01:22:01 AM PST