Thanks, Astro0. I think too your filled version deserves APOD publication....

By the way, they (APOD) did a great job with the links... one of the links is to the Rub al Khali mosaic. The colors in the two images compare favorably, I think:

Dilo-colorized clouds image
Rub al Khali

It didn't quite register with me what all this "APOD" stuff was about until I made my nightly pilgrimage to Astronomy Picture of the Day -- and then I had to come back to UMSF and add my congrats! Well done, guys.

Hi everybody. This is my first post here, after lurking for a long while. I will not be posting here very much as I do not have any science background, and are not able to contribute much.

But I do have a question that google doesn't seem to answer. Is it clear what these clouds consist off? And if or how the substance off these clouds condense and "rain"?

All information indicates these clouds are cirrus-type water ice clouds. Atmosphere temperatures are generally too high for CO2 dry-ice clouds, and the atmosphereic water vapor levels when these clouds are present are high enough (though very low) that clouds are expected to for.

CO2 clouds probably form during the polar night and were observed by the topography-profiling laser on Mars Global Surveyor.

Viking Orbiters repeatedly saw an unusual cloud at very high altitude in a topographically fixed location they concluded was also probably CO2 ice. The cloud had very sharp, high contrast features indicating fast formation and sublimation and was at an altitude where temperatures marginally allowed CO2 ice. The topographic location was mid southern latitude where vertical oscillations of a "jet stream" was thought to be induced by big topographic features like the Hellas basin.

Zoost,
Just to elaborate a bit on edstrick's answer. Cirrus clouds are composed of tiny ice crystals. When the crystals start to fall they vaporize very rapidly in the dry martian atmosphere. They would never reach the surface, at least in the low and mid latitudes. Things might be somewhat different at the poles, but someone who knows more about the subject than I would have to explain that.

I did read somewhere that it could snow around the poles of mars. Which would be a GREAT thing to see (one day, with a future lander) or perhaps MRO can show the snow clouds seen from above one winter.

I try often to relate what we see on Mars to what we see on Earth.
Here is what I've seen 2 days ago from my home :
Click to view attachment

I feel the "stitch" add for a more Martian-like picture.
Enjoy

Snow in the form we (And Calvin of cartoon strip fame) know and love is highly improbable on Mars. There's a small likelihood though that microscopic ice crystals could precipitate out of the atmosphere, but they have a long long way to fall. Falling ice crystals would also be quite volatile in the low pressure of the Martian atmosphere and I doubt they'd stand a chance of actually making it to the ground. Still, I'd love to read anything suggesting it might be possible.

I was trying to look around for some references that would explain whether the "snow" that's mentioned for Mars actually fell from the sky or just precipitated in place (making it more what I'd call "frost" though it would be deeper). I always thought it precipitated in place but there are lots of researchers using the word "snow" so now I'm really confused. Anybody have any insight?

--Emily

I'm not trying to help on this, but I imagine that "your" frost, Emily, could be blown by the wind and become to look like "real" snow for a short period of time.
Welcome back to brain (snow) storm UMSF

The MCS guys would be the first port of call I would have thought - I'm not sure what they're measuring, how they measure it and what they already know about it- but I've heard mention of them looking for snow like things in the polar regions at night.

Doug

Well I dont have any real insight, but I have always thought that the 'snow' imagined by Viking actually was hoarfrost.

Hoarfrost implies saturated air at the surface. Clouds imply saturated air at altitude. Opponents of 'snow' seem to be saying there must always be an unsaturated layer in between where descending ice particles would sublime. I don't see why.

Yes - that assumption presumes that any ice particle that forms will automatically sublimate in unsaturated air, yet if it's cold enough, it will not.

Doug

Here's a link that provides one viewpoint.

http://www-mgcm.arc.nasa.gov/mgcm/HTML/FAQS/rain.html

If the current vapor pressure was equal to the saturation vapor pressure throughout the atmosphere you'd have very thick clouds (somthing like nimbostratus on Earth, at least you'd have more clouds than are observed at lower altitudes). And there aren't any, that is what we see. Thus, the water vapor pressure is lower than the saturation vapor pressure below the martian clouds. Therefore, any ice crystals that fall down would sublime long before they'd reach the surface.

On Earth there are situations where falling precipitation (snow) does not reach the surface, too, because the air layer below is very dry. As the falling snow evaporates/sublimes, the underlying air gets enriched with water vapor until the saturation vapor pressure is reached. So, consecutively, the snow can reach lower altitudes until the whole airmass below the clouds is very moist and the snow reaches the surface. That only works well if the dewpoint is below 0°C between the clouds and the surface (otherwise the air mass does not get cooled below 0°C and the snow melts). That just happened in Denver, CO. Yesterday they had 17°C, but the dewpoint was very low (<0°C) below the clouds. And today you have snow in Denver and temperatures around 0°C. That resulted from the process described above.
Such a process could not occur on Mars under current atmospheric conditions as you need *a lot of snow* = thick clouds to moisten the whole layer of air below the snow producing clouds. There simply isn't enough water vapor.

Michael

Thanks for this link -- just in time for me to cannibalize it for my Planetary Radio Q and A

--Emily

Sure, that's what we see in the daytime. But in the middle of a polar winter night?

Yes, that is certainly true.

I remember now that I read a publication by some french scientists who modelled clouds induced by orography over the north polar regions (observed through MOLA?). These clouds were made of dry ice particles (CO2). I think they wrote something about possible small amounts of precipitation from these clouds, but CO2-ice crystals, not water. Can't find that publication any more, unfortunately.

Michael

From the link provided by MarkL I borrowed the folloing quote: "But theoretical calculations seem to suggest that generally such snow would not tend to reach the surface."

And I tend to agree, look at this image from February 1979 and I think you will agree with me that this look quite more like frost than a result of actual snowfall. The white frost/snow dont cover the entire scene as after a snowfall.

Yet on the page where the image are found the word 'snow' are used again. So the word seems to have been repeated quite often t describe whats seen on those images.

As a sidenote, on that page we see that the martian sky might display colours quite different from the rusty red that seem to dominate the ones made by the excellent image manipulators of this forum.

That's a very early morning image, with the sun off to the right, and the image has been stretched quite a bit to get the detail of the ground to show well, so the sky has been saturated.

Some superb results from the PDS released Viking camera data - http://www.astrosurf.com/nunes/explor/explor_vik.htm

Particularly - http://www.astrosurf.com/nunes/explor/viki...03calstrech.jpg

Doug

Clouds and Snow from MOLA

Corrosive snow

Here is a serie of 2 VL2 images showing the gradual condensation of water frost on Mars and then its full cover on the surface. The 1st image was taken in summer. The 4th image was taken early spring and shows its sublimation.
Enjoy !

Hi,

I processed those images, based on the gain settings on the Viking cameras and the color filter wavelenghts.

The MER images here: http://www.lyle.org/~markoff/ provide a good idea of the general brightness and color tone of Mars. They are, as best as I know, the only proper calibrated Martian images, because they were based on a large number of filters, that cover all the visible spectrum (MER images generated by using the 6 filters with gamma correction).

The important thing is that, after applying my processing protocol, all Viking images look consistent with the MER and Pathfinder results. Even sunsets and sunrises.

One thing that I couldn't correct was the camera gradient in the upper part if the image. So the sky still looks as if it darkens a lot above the horizon...

I believe there is some kind of obstruction that causes the darkening. Another problem with Viking color, which I am sure you have encountered, is that since the images were 8-bit selectively cut down to 6-bit for transmission, there are a lot of washed-out skies.

Yes, very nice processing and an interesting set of data. When I was playing with the Viking data, I think that there were few panoramas that showed the distribution of the frost around the site. One interesting thing would be to create some vertical projections of those and chart the evolution of the frost patches. I don't know if that was done at the time, but I think it would be an interesting project, provided that there are enough images.

Yes... that's apparent when I corrected the images for gain. See this one for example: http://www.astrosurf.com/nunes/explor/explor_vik.htm

I didn't try to change the original look of the data much, but in some cases I Just filled the sky with a uniform "general Mars Sky color".

That is what I was referring to...I have done the same. But my work has always been focused more on super-resolution...which is why I was thrilled when you draped your color data over some of my black and white images.

http://www.astrosurf.com/nunes/explor/viking/21i093_cal.jpg
Sorry, I wanted to include a direct link to this image.

When I worked with that image, I didn't even try to mosaic it wit that very overexposed set. In this version, I did some color cloning near the left side of the image to get rid of color noise caused by "salt and pepper" in the raw data.

The Viking Lander cameras had a clear-glass dust-shield that vignetted the extreme top of the field of view (I think 40 deg above the horizon) The vignetting was different for each color channel (not filter.. the cameras used physically separate photodiodes for each color band. 3 vis, 3 infrared channels, 1 broadband, 1 high opacity sun channel, and 4 focus-steps for high resolution imaging. The vignetting proved somewhat useful as it let Viking image closer to the sun in the sky for atmosphere scattering properties that would have been otherwise possible.

During the extended mission, they jettisoned one or two of the dust shields but saw little effect: not much accumulated dust.

Thanks all for the answers..

Snow or no snow.. White Mars is as MAGICAL as is Earth in with a white (snow/ice) cover

First results from the new smart software...
This is animation from 10 NavCam frames from Sol956, published only today:
Click to view attachment
(I flattened a little the frames in order to make clouds more visible in the bright/dark areas).
Clouds seems to generate near the center.

Gorgeous!

Now, about that colourised version...


Bob Shaw

That is absolutely cool!

Now we need animation from a dust devil too. Capturing a landslide (as long as the rover is not involved) would be neat also--but would the images be made fast enough under that circumstance?. What is the time lapse for these images?

About 30 sec/per image. See http://www.lpl.arizona.edu/~lemmon/mer_dd.html.

Here is the colourised version of the clouds animation.

Taken on Sol 956.

jvandriel

Some details on the sol 956 sequence in this press image description. It turns out it wasn't captured using the new software.

and - nice to see it on such a well known website - BUT....
http://www.space.com/scienceastronomy/0702...ars_clouds.html

Not giving proper credit AT ALL. Not my place to correct them, but I hope the people who actually made that image get in touch wite Space.com and get them to correct that. Even if it were a NASA released image - the credit would be NASA/JPL or NASA/JPL/Cornell

Not good work there by Ker Than.

Doug

Man...That's so disrespectful...

EDITED: On the "cover" the credits is NASA and GRL...
What does GRL stands for?

EDITED...again: GRL = Geophysical Research Letters?

This is how is SHOULD be credited...
http://antwrp.gsfc.nasa.gov/apod/ap061017.html

Doug

Did you already give that information to space.com?
If you didn't...

I shot off a quick email to space.com. I don't particularly care about the attribution myself, but they might want to get it right. APOD did it properly, so I sent them that link.

P.S. I don't plan to pursue it further, so if anybody else wants to, go ahead.

Space.com must gathering all the information about the contributors of the image before publish it.
I'm agree with Michael, [edit]"it's disrespectfull" ©Micheal Howard.
I will email the author too.

Hey! See if you give the proper credit to that statement!

They've changed it - and still got it wrong.

Close enough, I guess.

You missed the point, Ant: I never called it 'disrepectful', ustrax did.

Wow.. 2 years later . I forgot about... but re-found this site... to reply to myself
and now.. I know that my wish came true.. great clouds have been seen ... (by Phoenix) recently over the Pole
I am an extremely happy man...

So glad that I can experience this all..