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O.B. Toon (University of Colorado)
Mars is an exciting planet to study in part because there is such clear evidence that its climate has not always been as it is now. While there are numerous theories for how, and why the Martian climate might have changed two ideas stand out as being especially interesting. First is the idea that variations in the Martian orbit may have led to higher pressure regimes in the past tens of millions of years. I show that the evidence seems to be against such high pressure climates. For instance, the lengths of Martian gullies implies that all of them formed under conditions in which water would boil as it does under the present atmospheric pressure. Likewise, studies of polar CO2 deposits suggest that there is not enough CO2 present to substantially raise the pressure relative to the current epoch. Secondly, it is exciting to envision an early wet mars, perhaps teeming with life. However, we have yet to find a mechanism that could produce a warmer Mars than the one we have now except for brief periods of time. The ancient features on mars that suggest flowing water can be explained by a global downpour resulting from the aftermath of impacts.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.