Soil/Ground Temperature Options

[Guest_Maximus_*]

Q: Would the maximum temperature of the ground (near the surface) on mars be lower or higher than the maximum temperature of the atmosphere?

I would guess that it would be lower. Assuming high temperature fluctuations, the amount of time it takes for the ground to "warm" up is too long. Does anyone for for sure?

[Gsnorgathon]

Yes. (See figure 4.)

[marsbug]

I would have said no (ground is warmer) because the atmosphere absorbs at lot less of the suns radiation than the ground does. I only skimmed through the paper but it looks to me like the temperature graphs are air temperatures at different hights above the ground, not direct readings of ground temperatures. I believe viking did measure ground temperature directly and found it ten to fifteen kelvin warmer than the air, but I can't find the results. Could someone with more knowledge confirm this or set me straight?

[remcook]

Yes, I think temperature on the ground is hotter during day and colder during night.
Some google result of a model:
http://www.gfd-dennou.org/arch/odakker/wor...ish/1drisan.htm
(see lowest right plot)

[JRehling]

TES measurements of ground temperatures indicate a maximum ground temperature much higher than the highest temperature measured off-ground by Viking and Pathfinder.

Pathfinder measured temperatures at different altitudes and the lower the thermometer, the higher the maximum temperature. I don't think there's any conclusion other than that the ground is the *cause* of that, and is therefore warmer than the air a few centimeters above the ground.

I think the gist is that the cooling you would experience ascending from the surface of the Earth is greatly exaggerated on Mars. A few decimeters on Mars give you the same cooling-off that you would experience with a climb of a kilometer on Earth.

[ngunn]

A thin layer of warm air immediately above a sunbaked surface is commonplace on Earth as the cause of the mirage. Presumably the air is heated faster than convection can remove it upward. It would not be surprising if the same thing happened around midday on Mars. I would expect it to be a very near-surface effect, reversed at night, and more or less independent of the thermal structure of the atmosphere as a whole.

[dburt]

Don't forget dust devils that form during the day, owing to a warmer ground surface, and thermal inertia of solid rocks that, like concrete, stay warm long after sunset.

-- HDP Don

[Doc]

Don't forget dust devils that form during the day, owing to a warmer ground surface, and thermal inertia of solid rocks that, like concrete, stay warm long after sunset.

-- HDP Don

And that explains the reason why we probably dont see dust devils at Meridiani let alone extremely sandy areas I suppose.

You need rocky areas or sparsly rocky areas like Gusev where warmed rocks are ready to provide energy for dust devils to form.

[hendric]

Do dust devils not form on sand dunes? I would think that are the right time of the year or even day, depending on the sand dune direction relative to the sun, the sun-facing parts would be warmed, while the away-facing parts would be much cooler due to the this atmosphere, causing a convection that could lead to dust devils.