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Re: Meteorites on Mars


Stuart - 
     Now that the business of the Monahans and the Moon meteorites is
finished, the list is quiet, and it seems to be a good time to try to
answer your question. 
     Since Mars has only a very thin atmosphere, it is 
quite likely that most impactors make it to its surface
intact, as you point out.  But since they have been slowed down very
little by an atmosphere, they hit the surface of Mars at a speed of
around 26 miles per second, plus or minus the speed of Mars in its
orbit around the Sun.
      Most likely, when they hit, the impactors explode into dust and
very small fragments. If you take a look at the Pathfinder pictures,
you will notice how all the larger rocks look like they have been hit
by a shotgun blast. Since there is no one with a shotgun around [ :)
], it is more likely that these have been hit by very small pieces
exploding outward from impacts. 
      The smaller rocks in the Pathfinder pictures look jagged, and
most likely they were thrown out of craters when different impactors
hit around the Pathfinder landing site. Pathfinder landed near several
large craters, and immediately adjacent to some smaller ones.
      You will also see a red dust on everything, which 
was most likely formed by the impact on Mars of iron and stony iron
asteroids.  
      As for the folks at JPL, don't worry about them spotting
anything.  They are just starting to understand that the dominant
geological process on 
Mars for the last several billion years has been the 
impact of asteroids and comets, and not water erosion or wind erosion.
 NASA has this thing about sending men to Mars, and is hoping that
there is a lot of water there so that they can do this, so it is
likely that the understanding of what their pictures show will come
very slowly to the people at JPL, and also that they will be very
reluctant to acknowledge it.
      In closing, my guess is that if you were going to try to collect
something of value on Mars, fossils would be a better bet than
meteorites.

                                   Best wishes - 
                                       Ed

---STUARTATK@aol.com wrote:
>
> Hi All,
> 
> Following my recent - very warm! - welcome to the List, and a long
day  at
> work thinking about this, I thought I'd share my thoughts - and 
invite your
> comments - on martian meteorites. No, not meteorites from  Mars...
meteorites
> *on* Mars...
> 
> Okay, this is what got me started. Before heading out for work at an
 ungodly
> hour this morning, I was flicking through a recent SKY &  TELESCOPE,
and
> opened up the wonderful Pathfinder panoramic landscape  they
produced. Amazing
> picture, breathtaking... And as I looked at it,  picking out Yogi
and the
> other named rocks, I found myself thinking  "There MUST be some
meteorites
> there... right there on that flood  plain..!" And there have to be,
right? I
> mean, think about it. Mars  has a thinner atmosphere than Earth's,
so many
> more meteoroids will  make it to the surface intact, and although
the iron
> rich older  meteorites will have suffered in the oxidising climate
there will
> be  plenty of younger irons, and some pretty big stones there too
I'd  bet...
> 
> (Of course, this isn't a new idea, I'm not claiming it is. Anyone 
who's read
> RED MARS will recall the stunning passage in that book  where some
of the
> settlers stumble across a plain littered with irons.  If you haven't
read it,
> take a look.)
> 
> But I digress. Anyway, I went upstairs, booted up my PC and, without
 really
> expecting to see anything, started zooming in on some stored 
Pathfinder
> images, trying to pick out anything which looked vaguely 
un-martian. The way
> I figured it - and someone put me right here if  I'm adding 2 and 2
to get 10!
> - meteorites on Mars will have a  thinner, maybe lighter fusion
crust because
> they won't spend as much  time heating up in the atmosphere, but
they would
> still have *some* so  should be visible against the tans and
cinnamons of the
> martian  landscape... and with less atmosphere to plough through
wouldn't at
> least some be found in shallow craters, where they fell in dust
dunes  or dry
> lake beds?
> 
> Of course, I didn't find anything (Yeah, like the guys at JPL
wouldn't  have
> spotted something there before me!!) but I went to work with a  head
full of
> ideas and questions, and arrived home again with a few  thoughts and
fanciful
> scenarios which I'd like to share with you, if  only to make you
smile at the
> naivete and romanticism of a newbie...  :-)
> 
> Firstly, I'm wondering just what wonders await us on Mars. There
must  be some
> major strewn fields there just waiting to be found and  explored.
With Mars'
> proximity to the asteroid belt - and having those  two dinky,
battered little
> moons in orbit around it - surely there's  the potential there for the
> recovery of a quite frightening number of  meteorites..? 
> 
> List members who hate science fiction will scoff at these next
ponts,  but
> think about it... perhaps in the future Mars will be a meteorite 
hunter's
> heaven. Maybe, once the colonisation has settled into its  stride,
and there's
> a permanent manned presence there, there'll be a  huge demand for
meteorites
> found on Mars. Eager to top up their wages,  the first settlers,
feeding a
> rejuvenated market on Earth, may well  roam across the surface of
their new
> planet filling bags with irons  and stones, like families picking
strawberries
> on a farm on a sunny  weekend. 
> 
> Unchecked they could strip Mars of its meteorites, sending them the 
same way
> that the buffalo went in the early days of the settlement of 
America, so
> perhaps some kind of "Mars Heritage" organisation will  have to ban
their
> collection and exportation, protecting them in the  same way we -
try to -
> protect elephant tusks and the like? But I'm  sure some will still
risk it,
> I'm sure, and they'll feed the black  market in martian meteorites by
> smuggling undeclared specimens back to  collectors on Earth...
> 
> Here's another vision of the future if you'll humour me. If we've 
found
> pieces of Mars here, on Earth, then it's pretty likely we'll  find
peaces of
> Earth there, on Mars. (The KT event must have blasted  an impressive
amount of
> rock into space; surely some of it reached  Mars..?) Can you imagine
the
> excitement the discovery of the first  Terran meteorite on Mars will
cause?
> (Apart from the downside - maybe  it brought micro-organisms with it
from
> Earth, contaminating Mars in  the process..?) That rock will surely
end up in
> a Museum, illuminated  inside a tall display case, alongside the
recovered
> Sojourner rover  and Viking Landers, for the settlers to look at and
remember
> their  roots...
> 
> Of course, if there's one piece of terrestrial rock on Mars there'll
 probably
> be more, many more, and they'll no doubt become very popular  with the
> settlers. Maybe, just as we fashion jewellery from pieces of 
Gibeon, the
> settlers will turn pieces of terrestrial meteorites into  rings,
brooches and
> pendants. Maybe they'll be more than just simple  items of jewellery
though?
> Maybe they'll play a role in the inevitable  political future of
Mars? 
> 
> Imagine it's 2198, and - repeating millennia of terrestrial history
-  there's
> a flourishing independance movement on Mars. Now imagine you 
disagree with
> it. What better way to display your loyalty to Earth  than to *wear*
a piece
> of the Home Planet on your finger or breast? Go  ahead, laugh, but
don't we
> wear badges now to display our national  patriotism? Why not planetary
> patriotism?
> 
> Looking even further ahead - I asked you to humour me! - could there
 come a
> day when a martian government decides it wants the lost pieces  of
its planet
> handing back? This isn't as ridiculous as it sounds; you  have all
heard, I'm
> sure, of countries demanding the return of works  of art stolen from
them
> during a past war by an invading or occupying  army? Here in the UK
our London
> museums are stuffed full to bursting  of statues from Rome, mummies
and golden
> death masks from Egypt and  sculptures from ancient Greece. The
Greeks have
> been demanding the  return of the so-called "Elgin Marbles" for
years. Is it
> so ridiculous  to imagine a time when a martian government - or an
> electioneering  extremist, seeking votes - demands the return of all
the
> pieces of  Zagami, Nakhla and others from us? 
> 
> I know a lot of List members will be shaking their heads in
disbelief  or
> disapproval at my ideas, but that's okay. What's important is that 
we realise
> meteorites aren't unique to Earth. They're Out There,  waiting to be
found on
> other worlds, on the ash-grey floors of lunar  craters, on the
dried-blood
> flood plains of Mars and at its ice caps  too. At the moment we can
only
> collect specimens in our own back yard,  but one day we'll be able
to go
> further, and then I know - I just  know! - we'll find some amazing,
amazing
> things...
> 
> Okay, I've tossed a stone into the pond, I'll sit back and await the
 ripples
> with interest, but one final thought: one day they'll discover a
piece  of
> Earth on Mars. Hmmm. In light of recent "discussions" just imagine 
the
> frantic bidding there'll be here on the List when *that*  happens...
:-)))
> 
> Stuart Atkinson
> Cumbria, UK.
> 
> 

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