

Hidden water below antarctica provides hope for life on Mars - anigbrowl
http://www.theverge.com/2015/4/28/8507769/antarctica-salt-water-life-mars

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danieltillett
There is life on earth more than a mile below us all. You can sink a mine
shaft down almost anywhere on the surface and find life deep underground. If
we wanted to find life on Mars this is where we should be looking.

One this topic there is so much rock transfer between Mars and Earth (about
100kg a year) that both planets are effectively one ecosystem.

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ryandvm
That raises an interesting point. There are actually two different concepts of
life on Mars:

    
    
      1) Life that has a shared lineage with Earth life.
      2) Life that is unrelated to Earth life.
    

#1 would be neat news, but it wouldn't be particularly earth shattering news
(hah). As you mention, this would be through ejecta transfer - some primordial
bacteria hitching a ride on interplanetary asteroid impact debris.

The thing about #1 is that we're almost certain it's completely plausible. We
have extremophiles on Earth that live in conditions just as harsh as some of
the places on Mars. The tricky part would be getting them there. Sadly,
biological transfer between planets doesn't really help us fill in any of the
variables in the Drake equation...

But #2 - that would be incredible. If we were to find life on Mars _and_ we
could prove that it had no relation to life on Earth, that forcibly changes
everyone's cosmic perspective. Proving that life evolved independently twice
in the same solar system would mean the universe must be teeming with it.

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danieltillett
If I had to make a bet I would predict that we will find that there is life in
a number of locations within the solar system (Mars, some of the moons of
Jupiter and Saturn) and they will all be related to life on earth. The Earth
has a cosmic cold and has been sneezing in all directions for billions of
years.

One of the interesting things about bacteria is that there are two major
lineages here on earth (the archea and the true bacteria). Some people have
speculated that one arose on Earth and the other on Mars, but I doubt we will
ever find good evidence for this speculation.

