Quote:
Originally Posted by mswhin63
Hi Craig,
The last statement "Planetary Protection" is correct in all discoveries on Mars and other planets. To consider life "as we know it" formation of mars outside the Goldilocks zone and the formation of a magnetic field so many Gya are factors not determinable or not correlated in the information I have read so far. I don't have a lot of time to read though. (This is a point of interest not an argument).
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Hi Malcolm;
Thanks for your comment. I'm not quite sure I understand your point however, you have raised the water/magnetic field issue, and its impact on life.
So the story goes that "geological observations", suggest 'rivers and seas' of liquid water dotted the martian surface about 3.5Gya. The amount of water has been equated to a planet-wide ocean half-a-kilometer deep or more. For the planet to have stayed warm enough for liquid water, scientists assume that Mars had a greenhouse "blanket" of carbon dioxide atmosphere at least 1000 times thicker than what Earth has now.
That carbon dioxide is now mostly gone. So is the water. They either went up (the ions or neutrals reached escape velocity), or they went down (subterranian), or the 'geological evidence' is actually evidence of something else other than liquid water, (possibly CO2 sublimation runoff). If we assume water and CO2, and they 'went up', then the conclusion is that Mars' dynamo effect (giving rise to a once strong planetary magnetic field), must have ceased between 3.5Gya, and present day. (If they went down .. we'll find evidence of evolved life).
Accurate measurements of the present-day rates of loss of martian atmosphere have not yet been accurately determined, so they've got another mission called MAVEN scheduled for 2013.
If Mars
did have 'big liquid water', it had it 3.5Gya, because this is what the geological observational evidence points to. This corresponds nicely with the right amount of time for life to have started, and thus supports finding life on Mars, from this era.
Once again .. if they
don't find evidence of this life, then something has to give.
Either way ... both outcome(s) will be big news !
Cheers