Bobby. wrote on Jun 28^th, 2010 at 1:34pm:


That might be problematic. There are sedimentary rocks in Western Australia that are 3.5 billion years old, (BIF or banded ironstone formation) and  may represent fossils from the time that there was little or no oxygen in the atmosphere. The problem is that geologists can't agree whether they represent life or not.

http://www.absoluteastronomy.com/topics/Banded_iron_formation

On Mars, the evidence from Opportunity and Spirit, together with remote sensing shows that Mars never got to the stage where oxygen started to form in the atmosphere.

We have no idea how likely it is for life to form, and we have no idea how likely it is for anaerobes to suddenly start producing oxygen, resulting in their almost certain extinction, but making it possible for microbes that use oxygen for respiration to exist.

Consequently, if they  had oceans on Mars, which current research indicates,  they were acidic and very rich in iron and magnesium*, probably very similar to those on Earth in most senses.

The Earth's early oceans probably had more aluminium, sodium and potassium due to crustal differentiation, which never occurred to any great extent on Mars.  While there are clay minerals on Mars, they probably formed later than the so-called Noachian period which was the period with widespread oceans.

Apart from anything else, the Martian environment never had a global magnetic field like the Earth's. It was always more hostile, and probably contained strong oxidizing agents which tends to rip apart organic molecules.

While we'll never know for sure, I'd put my money on abiogenesis on Earth.

I read a paper somewhere that talked about probabilities of different scenarios. The Martian life origins scenario was in there, but was two orders of magnitude down compared to life originating on Earth. I've probably no hope of finding that paper again

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*That acidic environment is confirmed by the presence of magnesium and iron sulphates, and Goethite, hematite spherules etc at Meridiani Planum.

Bobby. wrote on Jun 28^th, 2010 at 6:10pm:


Well to start with, I don't discount the possibility that life could exist even today in underground fissures, especially near volcanic areas. A certain Italian researcher (Vittorio Formasino I think) keeps finding traces of methane  and formaldehyde in the atmosphere, so it's not impossible.

All I'm saying is that on the balance of probability, life probably originated here on Earth.

OK, the inference that you make doesn't really follow logically. It's like saying that salamanders can withstand extreme heat, therefore they can survive extreme cold. It's very seductive, but there is no rationale behind the statement.  It's certainly not impossible, but nothing you said there described the conditions that organisms would face on Mars.

There are many differences between the extreme conditions on Earth and on Mars. Liquid water is the big one, sodium chloride is another, a pH of around 8.3 is another, but the biggest one of all is the enormous pool of microbial life on Earth. It's that all-pervading life on Earth that makes such extremophiles possible, because it gives evolution a chance.  

On Earth, microbes have adapted to niche environments primarily because there is a big enough pool so that the best adapted organisms can survive these extreme conditions.

There is no evidence that there was ever a large abundance of life on Mars, and there is plenty of evidence that there is either no life or very little life on Mars today.  

Again, I don't doubt that it's possible that life could have originated on Mars first/ that there could be a God, but on the balance of probability, I don't think so, for both claims.

It would probably be nice if there was life on Mars or even if there was a God, but that doesn't mean that it's necessarily the case.

Can you see what I'm getting at? I'm saying that you're drawing a very long bow if you believe the theory that life began on Mars.

Of course, you've gone from 'believe that theory' to 'could possibly', so I think you understand.

Don't get me wrong. Faith can be a good thing.

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That doesn't rule out chimerism and multiple origins.

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It's just traditionally part of the theory 'package'. It becomes an assumption with inheritance and the branching tree bit. Nothing actually rules it out, because the theory is infinitely adaptive.

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Maybe I have the wrong term. I mean inheriting genetic info from two different species.

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It does exist - whole ecosystems that are based on consuming volcanic energy rather than solar energy.

Bobby. wrote on Jun 28^th, 2010 at 7:10pm:


I've heard people say that before, but I'm not sure where they got it from. The first oceans probably appeared on Earth about 3.9 billion years ago.  

The first oceans on Mars appear to have formed  late in the Noachian period, around 3.5 billion years ago, although the exact timing of Martian geology is subject to considerable interpretation. 

Both Mars and Earth formed around 4.5 - 4.6 billion years ago - about the same time as the solar system itself. We can tell that from isotope analysis.

There is no evidence that conditions for life were better on Mars earlier than on Earth. The other point is that the Earth rapidly developed a geomagnetic field, unlike Mars. There is evidence of some localised magnetism in the Southern hemisphere of Mars, but it never became a strong global magnetic field.

All this becomes important when we consider that the solar wind was about 100 times stronger 3.5 million years ago and the magnetic field deflected the worst of the solar wind (towards the poles).

The first conclusive life on Earth can be dated at about 2.9 Billion years ago. There are possible indicators of life 3.5 billion years ago from highly metamorphised deposits in Greenland, but these are by no means conclusive.  

To state that it is more likely that life originated on Mars, first you need to show that life actually formed on the more hostile conditions on Mars in the first place. We have no evidence that there was ever life on Mars, and we have plenty of evidence that there was never extensive life on Mars.  

Some researchers argue that the slightly alkaline conditions of the beginning of the Noachian. However it all depends what form that hypothetical life took. If it was bacteria that used sulfur or iron for their respiration, then the prime period would have been the end of the Noachian, by which time acidic seas had started to form.

For me, even though astrobiologists like to dream, Occam's razor seems to favour abiogenesis on Earth as the more likely scenario.

Let's put radiation levels in perspective. Radiation levels in interplanetary space today can rise to as high as 100,000 milli-rems per event in a flare, and constant exposure is approximately 1,000 milli-rems per day (30 times that on Earth, 10 times that on the Shuttle) and approximately double that on the surface of Mars (because it rotates). Approximately 80% of this radiation is in the form of high energy protons. Take conditions 3.5 billion years ago and you can multiply those radiation levels by roughly 100.  

Which kind of bacteria could have made the trip? Halobacteria? They would be the most likely to survive. They do pretty well in saline conditions, but not in high radiation conditions. Deinococcus radiodurans was certainly not around then.

Like you, I'd love to know whether or not there was ever life on Mars, but even if they find fossilised evidence, will it be convincing?

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As far as I know the first earth had an enormous collision with
another object which formed 2 objects:
one was the Earth & the other the moon.
This caused the whole Earth to melt & delayed the start of
life by 1 billion years compared to Mars.
Mars may have had more radiation but what if life on Mars
was protected by being in deep water?

Muso - are you saying that Bobby is wrong?

That's like saying that the Fonz is wrong!

Thanks Muso.
I am not a member of the Mars society but I am a member
of an astronomical society.
I live in Melbourne & I enjoy taking photos of the cosmos
& talking about cosmology.
I am of the opinion that the Earth  is just one part of
a much larger picture.
To say that life started here is too close to religion.
We don't know if comets seed the universe or whether
life started on Mars but we have good theories.
Maybe life can start anywhere given the right conditions?
I just hope that one day we'll have some evidence
either way.

Muso
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Science can now answer a very big question about our atoms.
Where will our atoms - we ourselves - end up?
Apparently one day the sun will swallow the earth  & we will become part
of a red giant.
Many 10's of billions of years after we will be sucked into a black hole at the center
of our galaxy.
Look up to the center of the Milky Way & that's where you're going!