Re: Mars Fossils

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I agree with Henry that extraterrestrial life forms may be difficult to
recognize, especially if our assumptions as to what constitutes life
ultimately prove to be too narrow. However, I'm not sure that conodonts and
calcichordates are appropriate examples. True, we didn't know much about
the phylogenetic affinities of these groups until we had a better idea of
what to compare them to. Nevertheless, I don't recall that the hypotheses
of conodonts and calcichordates being inorganic structures instead of true
fossils were ever taken very seriously.

I also like the idea of not being able to determine for sure whether an
"object" (e.g., a meteorite or some part thereof) that demands to be taken
to one's leader is alive or some sort of automation. In fact, I'll bet
there's a valuable idea for a science fiction book in that observation
alone. However, even if such an object did turn out to be a robot, wouldn't
that be evidence for extraterrestrial life?

I think we're back to the old proof of a negative argument here. It will be
logically impossible to prove that life does not exist on any other planet,
moon, star, etc. That's a given. The Mars fossil controversy revolves
around whether the available evidence proves, or even suggests, that life
did exist on Mars. All I'm saying is that it might make a certain amount of
sense to draw on the insights and experience of those who confront the
analogous problem of detecting signs of life during the early history of
our own planet; and (while you're at it) to acknowledge that those people
are paleontologists. That's being done to some extent, but I'd like to see
our field get much more good PR out of this than has been the case thus
far. To paraphrase the best quip I've heard on the subject, figuring out
whether there's life on Mars just might be an pretty good test of whether
there's intelligent life on Earth.


Norm MacLeod





>A point that nobody seems to have made.
>
>Comparative biology is impossible without comparative material. Without a
>suitable model, ultimately based on the extant biota, it is extremely
>difficult
>to interpret a fossil in a meaningful and testable way. Remember conodonts and
>calcichordates?
>
>Now then, extrapolate this to a putative 'fossil' that does not even come from
>our own planet. There is no a priori reason why extraterrestrial life should
>even be based on terrestrial chemistry, never mind whether it would exhibit
>forms comparable with earthly bacteria -- unless one has good independent
>grounds for believing in panspermia, or that carbon chemistry is essential for
>life (or by moving the goalposts so that life by definition must be carbon
>based).
>
>Even if some extraterrestrial phenomenon appeared to be related to the
>presence
>of life, it need not be. It could simply be 'inorganic', but how would one be
>able to tell? Wherefore martian pyritic dendrites?
>
>I suspect that it will be formally impossible to identify alien life-forms as
>such unless they step right up and demand to be taken to one's leader. And
>even
>then, there is no reason to believe that such a life-form is not an
>automaton or
>similar.
>
>It's life, Norm, but not as we know it.
>
>Henry
>
>______________________________ Reply Separator
>_________________________________
>Subject: Mars Fossils
>Author:  N.MacLeod@nhm.ac.uk at Internet
>Date:    18/08/96 04:08
>
>
>     The "discovery" of alleged fossils from Mars ...



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Norman MacLeod
Micropalaeontological Research
N.MacLeod@nhm.ac.uk (Internet)
N.MacLeod@uk.ac.nhm (Janet)

Address: Dept. of Palaeontology, The Natural History Museum,
         Cromwell Road, London, SW7 5BD

Office Phone: 0171-938-9006
Dept. FAX:  0171-938-9277
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