[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?

[RNeuhaus]

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?

The atmosphere presure is not related to DD but with the amount of water sublimited into the atmosphere from as low of 2 milibars to as high 9 milibars during the change of summer-winter sessions. The Dust Devil is mostly along with the increased of Tau is related with the temperature of atmosphere. According to the MOC pictures, I have noted that the most streaks of Dust Devil lays around the center of Gusev Crater, close to Columbia Hill.

Rodolfo

[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

[RNeuhaus]

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.

Yes, you are right, not only the temperature but also the pressure plays influence the amount of atmosphere pressure. I forgot it...It is nothing to feeling the atmosphere pressure of 1.2 kg/m3 at sea level.

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.

According to the paper: Journal of Geophysical Research-Planet (A climate database for Mars).
at Northern Hemipshere:
I 0-90 Spring
II 90-180 Summer
III 180-270 Fall
IV 270-0 Winter
- The highest atmosphere pressure at the Chryse Planitia (Viking 1 landing place 22 degree north) and at Utopia Plantia (Viking 2 landing place at 48 degree north) at the LS 265 which is the beginning of winter in the Northern Hemisphere.
- The second highest atmosphere presure is around LS 80 (spring in the Northern Hemisphere).
- The graphic shows like a sine wave starting 4.0 millbars as zero at LS 90 as reference. - The lowest atmosphere pressure occurs at LS 160 (summer in the Northern Hemisphere) and the second lowest atmosphere pressure occurs at 360 degree (winter at the Northern Hemisphere).
- It is evident that the atmosphere pressure is higher for the Viking's 2 place (most northern) than Viking's 1 place. There are daily minor fluctuations of pressure.
These fluctuations of atmosphere are caused by the sublimation and condensation of C02. However, with the general dust storms, the atmosphere pressure raises a little.
At the southern place, I expect that the atmosphere pressure will be the opposite to the northen place.

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

It is perfectly understandable. I think it so!. That is interesting.

To Myran, the wind speed varies with the surface temperature, air density and temperature and it is also sensitive to the landform. In the Gusev's crater there are lots of upwards winds due to its special geographic landform which is favourable to form Dust Devil at the center of Crater.

Rodolfo

[Guest_Myran_*]

Thank you Doug and Rodolfo.
Yes Gusev are indeed a dust devil engine, I had noted on exploratorium that the DD's have been considerably larger recently adding to that the report that the rover even have been rocked by a gust of wind, and wondered about the reason for that.
The answer seems to be that all factors boosts each other, with that including season & climate as well. Yes I cant help thinking that the overall climate read; the freezing of CO² at the pole are creating a tradewind between the hemispheres might be a factor to be reconed with for these winds. How large part that is, well we might not know until we have a set of netlanders.

[abalone]

The amount of water vapor in the atmosphere is dependent on the air's temperature and pressure --

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

The amount of water vapour in the atmosphere is not affected by atmospheric pressure. It is only influenced by two factors----- the temperature and the availability of water or ice to evaporate. The partial pressure of water at a given temperature is independant of any other gases or their partial pressure. So the partial pressure of water vapour would be the same if all the other gases disappeared into space but of course its % of the atmosphere would increase

The reason its 100% at night on Mars is for the same reason it is on Earth in lots of places, as it cools down at night maximum partial pressure decrease but the amount of water in the air does not. On Mars the temperature drop is much greater at night therefore more likely to be 100%.

[Guest_Myran_*]

The dust devils/whirlwinds get up in the hills also.

See upper left corner of this one: http://qt.exploratorium.edu/mars/spirit/na...DNP0630R0M1.JPG

[SigurRosFan]

Great finding!