[X] My Assistant

[Guest_Myran_*]

With the stronger winds and larger dust devils noted by several ones here.
Anyone know what the atmospheric pressure are now on Mars, and more specifically in the Gusev area?

[dvandorn]

The amount of water vapor in the atmosphere is dependent on the air's temperature and pressure -- not vice-versa. If there was absolutely no water or ice on Mars, but everything else was the same, we would see the same air pressure patterns.

I think, instread of water, you meant to say that as frozen CO2 sublimates into the air, the air pressure rises. Since the process is always going on at both poles (sublimating in the summer hemisphere and freezing out in the winter hemisphere), Mars' overall air pressure doesn't rise commensurate with the amount of CO2 released at a given pole; but the air pressure across the entire planet does fluctuate between about 3 and 9 millibars, depending on where in the cycle you're looking.

Also, Mars' northern hemisphere is significantly lower than its southern, which means that the air pressure tends to be a little higher in the northern hemisphere. It's also easier for gaseous CO2 to migrate to the north pole as northern winter approaches than it is for the reverse to happen -- it's heading downhill when flowing towards the north pole. But that's a very minor effect. The north polar ice/CO2 cap grows larger than the south pole's, and maintains a larger remnant cap during its summer, because Mars is farthest from the Sun during northern summer and closest to the sun during southern summer. And its orbital eccentricity is far greater than that of the Earth, so the difference in insolation between aphelion and perihelion is far greater than that on Earth.

One interesting thing I read once -- Mars' night-time atmosphere is nearly always at 100% relative humidity. In other words, while the extremely thin air on Mars can only hold a tiny, tiny amount of water vapor, Mars' air holds all that it can hold at night. Which brings up interesting possibilities for barely-noticeable precipitation events.

-the other Doug