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NASA Says Mars Rocks Formed in a Salty Sea
NASA has made another announcement, live on NASA TV, regarding the discoveries of the Spirit and Opportunity rovers. They believe that the rocks examined by Opportunity were actually formed in water; that those rocks were actually sediments laid down in a shallow salty sea. They've already had outside scientists examine their data and those scientists concur with the conclusions. NASA has a story with explanations and some photos.
Acidophiles.
There is no environment on Earth too extreme for life, as long as there is liquid water.
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No, salt accumulates in the oceans from the erosion of surface soils and rocks, as the minerals wash into larger bodies of water. This may mean that Mars once had rain.
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It (probably) got there in the first place during Mars' formation, and perhaps later due to cometary bombardment.
As to why it was lost, crudely put: evaporation into outer space.
Molecules of volatile gasses, including water vapor, that waft into a planet's upper atmosphere occasionally reach escape velocity and are lost.
Why some gasses and not others? There are a bunch of factors at work:
Heavier gasses -- CO2, for example -- require more energy to get up to escape velocity. They statistically hang around longer.
Larger planets have higher escape velocities.
Planets farther from the Sun recieve less insolation, so there's less of a chance that a molecule will get kicked up to escape velocity.
Except they missed the 2/29 deadline.
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During the news conference the possibility was raised that this water was under a protective layer of ice. So this could have happened without a thick and warm atmopshere.
The huge volcanos make it pretty clear Mars was once geologically active, I think.
The loss of oceans on mars has nothing to do with a loss in mass.
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The magnetic field Mars current has is not capable of protecting it's atmosphere by deflecting solar wind (the solar wind has been eating away at the Martian atmosphere for some time now; I'm not sure if scientists believe mars ever had a magnetic field capable of doing do, but as it's core has cooled off/solidified the magnetic field on the planet today is what it will always have).
As Mars's atmosphere is stripped away/blown into space, the atmospheric pressure drops. At a certain point, the pressure drops to a point where water cannot exist in liquid form and evaporates -- creating more atmosphere, which then gets stripped away by the solar wind
The cycle continues until all surface water has evaporated or frozen.
1. What evidence supports or rules out the presence of liquids other than H2O on the surface of Mars, at one time, in large quantities?
No evidence supports any such thing. Nothing rules it out, however, see answer to question #2.
2. How much, if any, of the present evidence could be explained by flows of liquid CO2, nitrogen, methane, ammonia, or some other liquid?
None. The chloride and bromide salts found are soluble in water, not any of those other liquids. By definition, chemical compunds classified as salts require the presence of water.
3. Which evidence, if any, points most strongly to the presence of large amounts of H2O as the liquid in question?
The presence of chloride and bromide salt deposits. They can't be formed any other way, but by precipitation from solution in water. The presence of hematite by itself is less conclusive than that, but in the presence of the salts, it adds to the certainty that water was present.
I know there are currently thought to be large, polar caps of solid H2O, but how much of the current evidence precludes the existence of large seas of some other liquid in the distant geological past?
The salt evidence excludes the other liquids.
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