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View Full Version : Ice deposits seen near surface in Mars northern plains.



RGClark
2009-Apr-01, 05:57 PM
Subsurface ice on Mars exposed by recent impacts.
19:22 30 March 2009 by Kelly Beatty, The Woodlands, SkyandTelescope.com
"Over the years spacecraft have glimpsed ever-finer features in the Martian landscape. These days, the HiRISE camera aboard NASA's Mars Reconnaissance Orbiter (MRO) can pick out objects only 0.3 metres in size; the High Resolution Stereo Camera on the European Space Agency's Mars Express is no slouch either, with a ground resolution of 2 metres.
"So HiRISE researchers were elated, but not particularly surprised, to discover some small, freshly gouged craters in images taken in 2008. Seen at five sites over a latitude range of 43 to 56 north, the excavations are typically 3 to 6 metres across and a third to two-thirds of a metre deep. One cluster must have appeared sometime between June and August, and a somewhat larger pit showed up between January and September.
"What did astound the team were splashes of white seen in and around a handful of these craterlets. Could it be water ice? Colleagues operating the spacecraft's CRISM instrument soon confirmed, for the one case large enough to yield a spectrum, that it was! Apparently fist-sized impactors had punched into a layer of ice hidden by a topping of dust about a third of a metre deep."
http://www.newscientist.com/article/dn16867-subsurface-ice-on-mars-exposed-by-recent-impacts.html

Here's the Lunar and Planetary Science Conference report referenced:

MODELING SUBLIMATION OF ICE EXPOSED BY RECENT IMPACTS IN THE MARTIAN MIDLATITUDES.
C. M. Dundas1, S. Byrne1, A. S. McEwen1 and the HiRISE Team. 1University of Arizona, Department of Planetary Sciences, Tucson, AZ, 85721 (e-mail: ****@lpl.arizona.edu).
http://www.lpi.usra.edu/meetings/lpsc2009/pdf/2168.pdf

At about a foot deep, this ice may be shallow enough to reach the subzero temperatures for melting ice with salt or perchlorate mixed in at least during Martian summer.


Bob Clark

JonClarke
2009-Apr-01, 09:14 PM
I was at the talk. The evidence was quite convincing. While some of the ice might be only a few 10s of cm down much of it is a metre of so, which is why it does not show up in the GRS/HEND data (which have pixels of several; 100 km).

Jon

marsbug
2009-Apr-02, 01:08 PM
Exposed ice so far south is very exciting! At the talk did they mention how many craters deep enough to churn up ice were forming per year?

JonClarke
2009-Apr-02, 07:50 PM
Exposed ice so far south is very exciting! At the talk did they mention how many craters deep enough to churn up ice were forming per year?

A question was asked about this, the short answer is they don't know. The craters loose their visible ice very quickly (over the period of observation) and become hard to distinguish from other small craters. The long answer is this is because craters small enough to turn up on a yearly rate are very small, and it is very tedious to look for them. Examples seen so far have turned up serendipitously. No doubt in a year or two there will be enough known to get a meaningful number. Especially if someone puts a slave (AKA grad student) onto it.

It also occurs to me that the presence of these craters and the frequency with which they form means that mission proposals like THOR (http://www.asu.edu/news/stories/200602/20060201_THOR.htm) may well be redundant.

CJSF
2009-Apr-03, 02:49 PM
Must....resist....too....strong...

The craters likely do not loose the ice. They lose it. I have noticed the use of loose instead of lose seems to be increasing. I know it isn't relevant to the heart of the discussion, but it makes my brain hurt!

CJSF

marsbug
2009-Apr-03, 05:40 PM
It also occurs to me that the presence of these craters and the frequency with which they form means that mission proposals like THOR (http://www.asu.edu/news/stories/200602/20060201_THOR.htm) may well be redundant.

THOR would give us control of the impact, and give us a 100% sure crater date, so we could watch the crater development from day 1. The THOR orbiter would also be able to look at naturally occuring craters, using the artificial one as a comparison. But if the cratering rate is high, and fresh craters easy to find, then the money spent on an impactor might be better spent on a better sensor suite for a THOR style orbiter. In either case a THOR type mission, using natural or artificial craters, looks like a great science opportunity.

JonClarke
2009-Apr-03, 10:25 PM
THOR would give us control of the impact, and give us a 100% sure crater date, so we could watch the crater development from day 1. The THOR orbiter would also be able to look at naturally occuring craters, using the artificial one as a comparison. But if the cratering rate is high, and fresh craters easy to find, then the money spent on an impactor might be better spent on a better sensor suite for a THOR style orbiter. In either case a THOR type mission, using natural or artificial craters, looks like a great science opportunity.

That's true, but mission opportunities are scarce and competition is fierce for them. I can see a good case for saying that we already have a great array of cameras, radars, spectrometers, etc. in orbit, more with MAVEN in a few years, with these craters being made all the time, we can get 90% of the data now, rather than waiting 10 years or more.

cheers

Jon

marsbug
2009-Apr-17, 12:15 PM
This is a fairly speculative observation, but is it likely, given the lattitude of these impacts, that any of the exposed ice could melt? I wouldn't expect a great deal of it, but over megayears occasional 'dampness' from ice exposed at low lattitudes by impacts like these could leave its mark on mars's rocks.

And it tempting to speculate that a rock from earth might land with just such an impact, leaving bits of itself mixed in with the exposed ice, and that some hardy cold loving microbe might find itself in an environment friendly enough for reproduction. Or that some crash landing space probe could do the same....

JonClarke
2009-Apr-17, 01:23 PM
This is a fairly speculative observation, but is it likely, given the lattitude of these impacts, that any of the exposed ice could melt? I wouldn't expect a great deal of it, but over megayears occasional 'dampness' from ice exposed at low lattitudes by impacts like these could leave its mark on mars's rocks.

And it tempting to speculate that a rock from earth might land with just such an impact, leaving bits of itself mixed in with the exposed ice, and that some hardy cold loving microbe might find itself in an environment friendly enough for reproduction. Or that some crash landing space probe could do the same....

I think it is possible, although the liquid water would be ephemeral. After all, there are concerns that a crash by an RTG equipped lander might well cause such melting in shallow ice, and a home for any hitch hiking microbes.

borman
2009-Apr-17, 05:30 PM
Albedo contrasts in polar dunes

Some time ago, some theorists brought up the possibility that south polar dune spots might be suggestive of a potential biological origin.

With the recent reports of “Blood Falls” in the Earth’s most southern region being associated with a special extremophile and the recent images from dune gullies from the MRO, I wonder if this will re-ignite a biological discussion regarding bacteria on Mars.

References:
Analysis of Dark Albedo Features on a Southern
Polar Dune Field of Mars
http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2007.0212

http://hirise.lpl.arizona.edu/ESP_011580_1255

Ancient Ecosystem Found in Ice Pocket
http://dsc.discovery.com/news/2009/04/16/glacier-microbes.html

http://www.nasa.gov/mission_pages/IPY/multimedia/ipyimg_20081009.html



Also, Jon, you might find this interesting:
An assessment of evidence for pingos on Mars using HiRISE
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-4VRX69P-1&_user=10&_coverDate=03%2F04%2F2009&_rdoc=49&_fmt=high&_orig=browse&_srch=doc-info(%23toc%236821%239999%23999999999%2399999%23FL A%23display%23Articles)&_cdi=6821&_sort=d&_docanchor=&_ct=101&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=2111efb4c83ac015bc03ee166e77dd7f

JonClarke
2009-Apr-17, 11:10 PM
Thanks!!!

marsbug
2009-Apr-18, 11:20 AM
This article (http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=384798) is also a good round up of the limits of ice and coldloving organisms. Most interesting is that there is some evidence for metabolism at temperatures as low as minus 40.

Edit: It has often been said that the problem with water on mars is that in areas where the conditions are right there is no ice and no mechanism for bringing ice there, in areas where there is ice the conditions are only favorable for vapour or ice, and by and large this seems to be true. The exposure of preserved ice to the surface in areas by meteorite impacts shows that there are to this day exceptional events that can leave ice exposed in an area where melting is possible. I kinda doubt it's common enough to sustain life but it could well impact our interpretation of martian geology.

marsbug
2009-May-07, 12:01 PM
With some more thought I wonder if areas of ice excavated by small impacts have been considered by NASA when they did their study on special zones (here) (http://mepag.jpl.nasa.gov/reports/MEPAG_SR-SAG_final1.pdf) that terrestrial life could propogate in? I had a skim through and I didn't see anything on the idea. I think it's worth them considering, as it seems possible that a crash landing probe could create it's own briefly lived special region based on the above discussion.

JonClarke
2009-May-07, 09:57 PM
With some more thought I wonder if areas of ice excavated by small impacts have been considered by NASA when they did their study on special zones (here) (http://mepag.jpl.nasa.gov/reports/MEPAG_SR-SAG_final1.pdf) that terrestrial life could propogate in? I had a skim through and I didn't see anything on the idea. I think it's worth them considering, as it seems possible that a crash landing probe could create it's own briefly lived special region based on the above discussion.

I don't think they were known about when the study was done. But they do show that the issues the study addressed have some basis in reality.

Jon

marsbug
2009-Jun-01, 11:42 AM
Some thread necromancy, but I thought I'd seen something like this article. (http://news.nationalgeographic.com/news/2007/05/070502-mars-ice.html) It suggests a very good reason why some craters turn up ice and some don't: the ice has been shown to be patchy even at high lattitudes.

samkent
2009-Jun-01, 04:31 PM
Maybe we should send a one shot lander to make sure it’s water/ice?

Oh been there, wasted that.

JonClarke
2009-Jun-01, 10:31 PM
Maybe we should send a one shot lander to make sure its water/ice?

Oh been there, wasted that.

What would it take to change your mind?

marsbug
2009-Jun-02, 10:58 AM
Maybe we should send a one shot lander to make sure its water/ice?

Oh been there, wasted that.

It's a good idea! As I suggested earlier exposed ice at those lattitudes could well produce ephemeral liquid, and that in turn might be having an impact on our understanding of martian geology and history.
Lots of little impacts producing trace water over billions of years = lots of evidence of trace water!