Ice image

JonClarke · Jun 16, 2005

I thought you might like this great image from last week’s Nature (Vol 435(9), p 723 June 5th 2005). It is a Mars Express HRSC image of a 35 km wide crater at 70 degrees N. It shows a 200 m thick water ice deposit and frost on the crater walls. The crater’s rim is 300 m above the plain, so there has been some vertical exaggeration. While there have been many awesome HRSC images, I think this is the most beautiful. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

silylene old · Jun 16, 2005

wow! <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center">- - - - - - - - - - - - - - - - - - - - - - </div><div class="Discussion_UserSignature" align="center">I really, really, really miss the "first unread post" function. </div> </div>

tom_hobbes · Jun 16, 2005

Like God's own oyster harbouring the mother of all pearls. <div class="Discussion_UserSignature"> I wish I could remember But my selective memory Won't let me - Mark Oliver Everett </div>

telfrow · Jun 16, 2005

An amazing image. Thanks for posting it Jon. <div class="Discussion_UserSignature"> Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild. - Tennyson </div>

tom_hobbes · Jun 16, 2005

Is there anywhere I can get a high-res of that Jon? Having trouble finding it. <div class="Discussion_UserSignature"> I wish I could remember But my selective memory Won't let me - Mark Oliver Everett </div>

grooble · Jun 16, 2005

Is this real? How much water could that become?

emho · Jun 16, 2005

I was wondering the same thing, how were they able to determine that it is water ice? I found this on their web site which is a PDF of the article: http://www.nature.com/nature/journal/v435/n7043/pdf/435723b.pdf

voyagerwsh · Jun 16, 2005

Great high resolution image of frosted crater by Mars Express, once MGS/MOC had older images of frosted craters with some frost deposit on the rims as well as crater floors.-- http://www.msss.com/mars_images/moc/nov_00_craters/ Viking 2 also had frost deposit images at Utopia Planitia.

igorsboss · Jun 16, 2005

Was this formed by a buildup of frost deposits from the atmosphere, or upwelling of liquid water from under the crater? Frost deposits would take a long time to form. Upwelling would take a short time to form.

tom_hobbes · Jun 16, 2005

Top right of those four does appear to be the same crater (I could be mistaken) though different angle of view and time of day. <div class="Discussion_UserSignature"> I wish I could remember But my selective memory Won't let me - Mark Oliver Everett </div>

voyagerwsh · Jun 16, 2005

Size wise they may not be same crater. Unnamed crater in MOC is about 48 KM across, while the crater in Nature measured at 35 KM wide.

yurkin · Jun 16, 2005

That’s an amazing picture. If you look at the MGS images The top right crater in image MOC2-258b appears to show the exact same crater seen in the Journal of Nature image. Looking straight down, rotated 90 degrees, with a lot more frost I think it’s the same crater. The MGS one is browner and a lot less vibrant but it may have just been the lighting at that time of day. The description says 70N and 35km across and in MGS it says 71N and 48km. I think the difference in diameters could easily be from how the crater is mearsured.

JonClarke · Jun 16, 2005

Logging in from work as my home computer has died... Thanks for someone providing a link to nature. I just assumed that people couldn't access the original as most nature stuff requires subscription (which I get from work). There was a lot of MOC images taken of this crater in the early images. The crater is easily located, as it is the only major feature at those coordinates of ~257W, 70.5N. The white patch and south crater wall frosting are visible in all but one image, suggesting that they are indeed a semi-permanant feature. Some examples: http://www.msss.com/moc_gallery/ab1_m04/images/M0202144.html http://www.msss.com/moc_gallery/ab1_m04/images/M0001895.html http://www.msss.com/moc_gallery/m19_m23/images/M23/M2301915.html http://www.msss.com/moc_gallery/e01_e06/images/E03/E0302478.html http://www.msss.com/moc_gallery/m13_m18/images/M15/M1501569.html (the only one where it appears absent, but it could also have been taken in winter when the whole region was covered in frost). The white material clearly blankets the surface, masking small scale underlying features such as ground patterning but not medium to large features like dunes. From this I would suggest than the white material is 10's of cm to metres thick, but not hundreds of m, as nature article suggests (could that be a typo?). Snow is the most likely explanation, as it is much thicker than the frosting on the walls. The concretic pattern seems to be a feature of the und <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

centsworth_II · Jun 16, 2005

I knocked the end period off your last link to get it to work. http://www.msss.com/moc_gallery/ab1_m04/images/FHA00768.html I was not aware of so many ice-covered crater bottoms. The one in Nature is so spectacular, but I wonder how much of that is due to the sylistic image treatment. I wonder how that frozen lake would look to MARSIS (200m thick!?). As I understand it, there is not a lot of difference between ice and rock to MARSIS, but it should still see the boundary between the bottom of the ice and the crater surface beneath it. <div class="Discussion_UserSignature"> </div>

JonClarke · Jun 16, 2005

Dunno! But it would be minor, I suspect that aspect is more important The thing to remember is that the crater floor will collect snow and frost because it is sheltered, much the same was as it will collect sand. The fact that it is shaded much of the time will mean that it is less likely to sublime as well. No too different to what controls the preservation of snow patches on earth well into summer at high latitudes and altitudes. Also don't forget that this still nameless crater is the most southernward example of such an ice filling. Korolev is only two degrees further north and has a much more extensive ice deposit. The freshness and whiteness must point toards this being a dynamic feature, renewed every year, just like the polar caps. There are some THEMIS images as well. Summer http://themis-data.asu.edu/img/V11755003.html Winter http://themis-data.asu.edu/img/V10844002.html All these images illustrate the complementarity of the different systems. MOC - very high resolution, panchromatic and narrow view. THEMIS - multispectral (false colour) regional coverage, medium resolution. HRSC - medium-high resolution, multispectral (near true colour), stereo coverage. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

silylene old · Jun 17, 2005

The white material clearly blankets the surface, masking small scale underlying features such as ground patterning but not medium to large features like dunes. From this I would suggest than the white material is 10's of cm to metres thick, but not hundreds of m, as nature article suggests (could that be a typo?). Snow is the most likely explanation, as it is much thicker than the frosting on the walls. Steve and Jon, I too had the very same distinct impression of thin ice and could not understand why the Nature article suggested the ice was hundreds of meters thick. I think the concentric rings could be formed by changes in the "shoreline" as the ice thickness grew or fell. The visible shoreline could be the result of windblown dust caking up against the ice deposit, and then perhaps being fixed in place due to the formation of a salt crust on the dust surface. If the ice later sublimes, this would leave a ring in the dust at the old shoreline, and a new shoreline could form at the new edge-of-the-ice location. I don't know the mechanism of the ice increasing in thickness. I really doubt liquid water ever existed, as some have suggested. I assume it is most likely that the ice increased in thickness due to slow accretion of water vapor from the atmosphere during colder times. Perhaps very careful examination could show that the formation of the concentric rings from ancient shorelines of ice is correlated to changes in Martian obliquity and the resultant different climatic conditions. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center">- - - - - - - - - - - - - - - - - - - - - - </div><div class="Discussion_UserSignature" align="center">I really, really, really miss the "first unread post" function. </div> </div>

JonClarke · Jun 17, 2005

Obviously the image is tweaked to get the best visual impression. remember "white rock" which was not that white? But the features is so white, so much more opaque than the frost, and even shows through the frost in the winter image, i think that it really is white. I would be interested in the evidence for it being 200 m thick. I can't see this being the case from the MOC and THEMIS data. But HRSC does give excellent topographic data. But it could also be a typo - 200 cm or 200 mm. Incidently, the THEMIS images I linked were daytime visible. Here is a day time thermal IR http://themis-data.asu.edu/img/I11755002.html Note the cooler (darker) appearance of the ice, and the clear underlying dune and concentric pattern. The only decent night thermal IR image is: http://themis-data.asu.edu/img/I05183035.html again the ice deposit is darker, showing that it is colder than the surrounding terrain. The fact that the ice is dark in both images shows that it has a very high thermal inertia, consistent with ice. I have never worked with radar but I know that airborne radar has been extensively used in Greenland and the Antarctic to map both the ice surface and the bedrock topography. Not sure how their frequncies compare to MARSIS though. I am really looking forward to the high resolution 3D image (the one in Nature would have been down sampled). Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

thalion · Jun 18, 2005

Thick ice or not, it's a fantastic image. Thanks for posting it!

tom_hobbes · Jul 30, 2005

ESA have now released the full size image Jon. And it's truly breathtaking: ESA: "The circular patch of bright material located at the centre of the crater is residual water ice." http://www.esa.int/SPECIALS/Mars_Express/SEMGKA808BE_1.html#subhead2 New Scientist article: "The ice is present all year round, as the temperature and pressure are not high enough to allow the sublimation of water ice, say ESA scientists. And it cannot be frozen carbon dioxide since carbon dioxide ice had already disappeared from the north polar cap by the time the image was taken - late Martian summer." http://www.newscientistspace.com/article/dn7755-frozen-lake-shines-bright-in-martian-crater.html <div class="Discussion_UserSignature"> I wish I could remember But my selective memory Won't let me - Mark Oliver Everett </div>

tom_hobbes · Jul 30, 2005

A nice reduced but sharp version. <div class="Discussion_UserSignature"> I wish I could remember But my selective memory Won't let me - Mark Oliver Everett </div>

grooble · Jul 30, 2005

I guess this would be the ideal site for a mars colony right?

cuddlyrocket · Jul 30, 2005

No, as it's too far north meaning the temperatures would be severely cold during the northern Martian winter (when the CO2 starts freezing out of the atmosphere). Also, there would be constant darkness for a fair portion of the year. A Mars base should be near the equator. However, you might want to mine it during the summer months. Send a planetary hopper. Melt the ice and electrolyse the water for LOX/LH2 fuel for the return trip. I suspect though, that we'll find a water supply nearer the equator before we're ready to send people.

aldo12xu · Jul 30, 2005

If anyone's interested I animated the original image released by Nature and created a video simulating a flyover the ice crater. I'd love to redo it with the recently released higher resolution version, but it would be a bit time consuming. So, anyways, you can watch the video by going to my video page and scrolling down a bit.

aldo12xu · Jul 31, 2005

I've enhanced a portion of the ice cap and it seems, as Jon and Steve have suggested, that the ice is far less than 200 metres thick. It looks like the white ice overlies a more dust covered lobe below it. http://www.marsgeo.com/Photos/Orbiters/Express/Ice-Crater2e.jpg

aldo12xu · Jul 31, 2005

Another perspective, showing the "ice" clinging to vertical cliff faces and how it generally follows topography. If it was a frozen lake, it would be confined to one topographic elevation and any high points rising above the ice level would be barren. But here we see that both high and low points are covered white. http://www.marsgeo.com/Photos/Orbiters/Express/Ice-Crater2ee.jpg

Ice image

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