whether phoenix mission (which is arrive at the surface of mars most recently) has find anything about "raining on mars",? I think abundon mithane raining quite possible on mars !!

is there a cycle every year as far as rainy season on mars followed !

or mars is not having any "raining history".

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Cold as Mars is, it's still way, *way* too hot for methane rain. Not to mention that there's so little of it in the atmosphere to begin with.

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Mars has no rainy season. In fact, it has no rain at all. There is a lot of water on Earth, and the range of temperatures on the surface and in the atmosphere is such that water can change back & forth between solid, liquid & vapor. Indeed, this ability of water to experience a phase transition is the primary driver of what we normally call "weather" on Earth.

But on Mars, things are very different. The range of temperatures is far larger than is the case on Earth, but except for some few extremes, the temperature on the surface of Mars is almost always well below the freezing temperature for water, and is literally always below that temperature in the Martian atmosphere. And because the atmosphere of Mars is only about 1/1000 of the density of Earth's atmosphere, it could hold very little water vapor anyway, even if it were warm enough. Since there is no way to get water vapor to hang around in the atmosphere so it can condense into liquid, there is no way to get rain on Mars.

So far as I know there is nothing else that can rain on Mars either.

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Earth extreme temperatures have been recorded from -110 f to plus 140 f, a range of 240 degrees f. Likely Mars is never as warm as 40 degrees f, but I don't think Mars gets as cold as -210 degrees f. If it does occasionally get that cold, it could snow carbon dioxide = dry ice. Carbon dioxide does not have a liquid state at low pressure. The carbon dioxide partial pressure at the surface of Mars (lowest elevation) is 3 to 6 milibars depending on the season. Is one milibar of water vapor partial presure possible at 20 degrees f? The atmosphere of Mars averages 90%? carbon dioxide. Neil

The highest temperature I recall seeing for Mars was about 80 F, but according to Extreme Planet Takes Its Toll (12 June 2007) the temperature extremes measured by the Spirit Rover go from a low of about -130 F to +95 F, which is warmer than I expected. Those temperatures are measured at the rover, on the surface. Since the atmosphere is very thin, the temperature falls off fast with altitude. So it will not be warm enough even in the lower atmosphere for water to do the rain thing.

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Is there a possibility of CO2 snow during a polar winter? (around -110 deg F)

Wiki says the min temp is -125 deg F, so I would imagine it's possible, though there may be sublimation issues given the extremely low pressure.

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I don't know about "snow" but the polar caps get CO2 added to them in the winter.

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Oops, Bad Meteorology alert!
Air does not "hold" water vapor. Gas pressures (including water vapor pressure) are independent of other gases. This is true for water vapor whether on earth or mars.: The low water vapor pressure on mars is not caused or limited by low atmospheric pressure - but by limited water and temperatures.
http://www.ems.psu.edu/~fraser/Bad/BadClouds.html
http://fermi.jhuapl.edu/people/babin/vapor/index.html

The pervasive martian dust everywhere is a very strong contraindication to rain. The reason we don't have dust that fine everywhere on Earth and in our atmosphere, is because we have rain. If there were rain of any sort on Mars - it would clear the atmosphere, and the fluid erosion would rapidly wash away the layer of fines that falls from the atmosphere over everything.

Doug

Re Mugaliens:
IIRC, though it can theoretically get cold enough for dry ice on Earth (if not at the surface, then certainly at altitude), the partial pressure of CO2 in our atmosphere is too low for it to occur.

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"Call me old-fashioned, but I think fire is magic. And it scares me a lot."

--The State

Mars atmosphere is only I/100 of the density of Earth's atmosphere.

There is the possibility, yet, of an extraordinary rain on Mars, by passage of a supernova shock front. For a transitory period, gas and dust from a supernova shock from a distance as far as 10 light years away...such as the one evidenced in sediments by Fe-60 marine deposits on Earth by Fields et al, presumably from Sne blasts in the Local Bubble from OB stars from the Centaurus-Sco Association.
So it would be rare, but not inconceivable. A meteor shower of fine dust, rich in iron oxides,aluminum oxides, pyroxene, olivine followed by atmospheric occluding, and rain. What would look good for this scenario is isotopic analysis of Martian soils to find Sne isotopes by the Mars Science Laboratory.

see:http://www.journals.uchicago.edu/doi/abs/10.1086/427797


pete

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