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Ice Lake on Mars
DecoDragon writes "The ESA's Mars Express discovered an ice lake on Mars. The ESA has a number of images and an explanation of what was found. The lake was found in an unnamed crater. The report says it can't be carbon dioxide, because carbon dioxide ice had already disappeared from the northern polar cap at the time the image was taken." Coverage from the BBC also available. From the article: "The team has also been able to detect faint traces of water ice along the rim of the crater and on the crater walls. Mars is covered with deep gorges, apparently carved out by rivers and glaciers, although most of the water vanished millions of years ago. "
Nice pictures. I think the article has one thing wrong, though. It should be possible for the ice to sublimate away above -103 F on Mars. Unless, of course this particular crater never gets that hot...
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Well, the only evidence of life is that which exists on Earth. On Earth, where there be water, there be life. The statement "All life needs water" is supported by the evidence. The evidences scope, however, is rather narrow.
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Not a joke, still from the Astronomy Picture of the Day site, is this picture, which according to the page text, was actually taken back in February, and reported in the June 2005 issue of Nature. So while it's news, it's not new news.
really. IANARS*, but how did previous missions miss that? haven't we already imaged most or all of the martian surface from orbit at a resolution high enough to see this glaringly obvious bullseye?
Well, this patch of ice looks like it has a surface area of what, 75 square km? All of Mars is about 145 million square km, so we're talking about 0.00005% of the surface -- I can kinda see how that might take a while to notice.
Basically, planets are big -- Mars may be smaller than the earth, but since there's no ocean, it has about the same land area.
Assuming that meteorites strike Mars fairly evenly, it should be possible to guess how old the ice lake is. It is certainly newer than the crater it is in (duh!) and from the lack of craters on the ice or in the crater the ice is in, there must be a very definite upper limit to how old it can be.
There are two possible sources for the water (an issue the ESA and NASA don't really discuss on their sites): We know there's an underground ice lake, for a start. It is possible that when the impact occured, it burst through to such a lake, melting the water temporarily. The water would reach the surface and re-freeze.
The second possibility is that the surface has indeed been warm enough for liquid water, despite evidence from those with martian meteorites. This is possible, as the meteorites may well have been from a cold part of Mars. It could well be that Mars couldn't -sustain- warm temperatures, so warm regions were geologically active regions. Water takes finite time to freeze, especially when flowing, allowing for water-formed features even outside regions that would have sustained liquid water.
The latter explanation would be great for those looking for life, but the ice-spray on the rim of the crater, along with the bulge of land under the ice, is more indicitive of the former. Rats!
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When you decrease the atmospheric pressure, you change the freezing and boiling point of water. Under pressure, water favors being a liquid. Without such pressure, the melting point and boiling point would come closer together.
For more info see this PDF (in particular, figure 5.1). It illustrates the triple point.
Except for the fact that the average surface temperature of Mars is -63 C, the atmospheric pressure is 100x lower than earth and the O2 composition of the atmoshpere is about 1,000,000x less.
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It's pretty clear that life requires a solvent of some kind to form the complex molecules needed for life. Try and imagine amino acids forming in ice or some other solid. Water is regarded as the universal solvent since virtually everything will dissolve in it. Add to that that water is pH neutral and it provides a very hospitable environment for these molcules.
Also, water has the unique property of being less dense in solid form than liquid form, hence ice floats. Thus, when bodies of water freeze, the ice settles on top of it. In other words, water freezes from the surface down, unlike other liquids. This action provides an insulating layer which allows life to flourish under the surface instead of being driven to the surface by ice forming from the bottom up.
Water also has strong surface tension due to the hydrogen bonding between water molucules. This allows for capillary action in which plant can pull water up against gravity. This isn't necessary for the formation of primitive life, but it's difficult to imagine higher forms of life without it.
No, all science points to water being the one molecule which is able to nurture and sustain life. It's an amazing compound despite the fact that it's so prevalent that we tend to take it for granted.
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