New minerals point to wetter Mars

[glenc]

http://news.bbc.co.uk/2/hi/science/nature/7696669.stm
A Nasa space probe has discovered a new category of minerals spread across large regions of Mars.
The find suggests liquid water remained on Mars' surface a billion years later than scientists had previously thought.
The US Mars Reconnaissance Orbiter (MRO) spacecraft found evidence of hydrated silica, better known as opal...

[Barrykgerdes]

What I want to know about Mars is. If Mars has a carbon dioxide atmosphere why hasn't it got a run away green house effect to make it too hot like the so called experts are telling us about Earth which only has a minute amount of Carbon dioxide in the atmosphere and that is part of the carbon cycle that keeps us alive?

The answer of course is Earth is in the habitable zone and our weather is 99.99 % controlled by the Sun.

Barry

[glenc]

Mars is currently 1.54 AU from the Sun, and the Sun is 2.37 times fainter than here (42% as bright), according to the inverse square law.

[AstralTraveller]

Firstly Mars only receives about 43% of the energy per square metre that falls on Earth. So the greenhouse effect would have to be much stronger before temperatures could 'run away'. To my mind the term 'run away' is only valid if there is a positive feedback involved (ie CO2 caused temperature increase releases more CO2 which causes a further increase).

Secondly although Mars' atmosphere contains 9 times more CO2 than Earth it only contains about 0.001 the amount of water vapour as Earth. On Earth the most important greenhouse gas, by a long long way, is water vapour. It accounts for the great majority (figures not at hand) of our 32 degree natural greenhouse effect. This is one reason (there are others) why a doubing of CO2 concentration can not result in a doubling of our greenhouse effect. A quick, nasty back-of-an-envelope calculation suggests that if CO2 were the only greenhouse gas and the response was linear then temperatures would have risen by 9 degrees since the industrial revolution! Clearly any effect is much much smaller.

BTW the greenhouse effect on Mars is 5 degrees.

[Ian Robinson]

If Mars was a wet planet for hundreds of millions of years longer , then the possibility that Mars developed some kind of biology too is now very much greater.

[Jen]

:screwy::screwy::screwy: still so many questions about this amazing planet :)

[Ian Robinson]

We might turn out to of marsian ancestry yet.

[Jen]

:P
:cool::cool::cool: