
Will we kill or contaminate microbial life on Mars? - jonbaer
http://www.kurzweilai.net/will-we-kill-or-contaminate-microbial-life-on-mars
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CoryG89
One thing I wonder about is if we go to Mars and find microbial life at some
later point. Will we ever be able to be sure that the microbes were there
before us, or did we bring them with us without realizing, after which they
reproduced until we detected them?

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fractalwrench
If we contaminated Mars with microbial life from Earth, it would have a
similar genetic signature to sequenced organisms on Earth. Assuming we could
get a DNA sequencing machine up there, it would probably be obvious that the
organism originated from Earth unless it was some previously undiscovered
Archaea.

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CoryG89
Sure, assuming that we find life that is significantly different than life on
Earth. If all we find is microbial life that is genetically similar to that on
Earth, then you might be inclined to believe we brought it there, but it seems
possible there might be no way to know for sure.

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curtis
The Martian surface is bathed in radiation, a near vacuum, and very, very dry.
If there is life on Mars, I think it is likely to be far enough underground
that nothing we do short of outright terraforming the planet is likely to make
any difference to it.

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kristianp
And yet every mission to Mars has a major component searching for evidence of
life e.g. [1]. How long before space agencies stop bothering? I guess the
whole "could be evidence for possible biological activity" thing is only part
of the science, but it annoys me that its given such a large apparent weight.

[https://en.wikipedia.org/wiki/ExoMars_Trace_Gas_Orbiter](https://en.wikipedia.org/wiki/ExoMars_Trace_Gas_Orbiter)

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John23832
Considering they have evolved in two totally separate (millions of miles away)
environment for millions of years, I'd doubt that microbes from Earth could
have any meaningful direct interaction with microbes on Mars.

Some people have seen too much Independence Day/Twilight Zone.

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GarrisonPrime
I wouldn't be too sure about an inability to interact. Given what we know
about the fundamental laws of chemistry, it's entirely possible that the
formation of life as we know it may be the only real way life can form. I
wouldn't be too surprised if we discovered microbes that look and function
very similarly to our own viruses and bacteria, etc., including DNA/RNA or
some very closely similar molecule and mechanism.

But overall I agree with you. There are likely to be many differences, and
even if they were exactly like Earth microbes the chances of them bothering us
or us bothering them would be just as unlikely as a chimpanzee catching a cold
from an iguana.

I think it much more likely that they could be biological irritants or even
toxins, if indeed they affect us at all.

I think the main concern is that we'd want to study them as isolated
lifeforms, and any Earth proteins or other contaminants would greatly hinder
such studies. Even if we could clearly separate out the contaminants, we
couldn't be certain if the Martian organisms had reacted to the Earth
substances in some way.

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John23832
> Given what we know about the fundamental laws of chemistry, it's entirely
> possible that the formation of life as we know it may be the only real way
> life can form.

Our form of life _could_ be the only kind possible, but that's nowhere near
proven as fact.

I agree with the rest of your statement though.

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gjolund
Historically the answer has been "Who cares?".

