Islands of ice on Mars and Pluto


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Ice-filled craters near Martian south pole

In a paper published today in the Journal of Geophysical Research: Planets, scientists describe the identification of 31 ice-filled craters in the high southern latitudes of Mars. The map to the right, from their paper, shows the locations of these craters. The scientists also took a look at Pluto, and found five craters there that had similar features, though these were likely filled with frozen nitrogen, not water ice.

From their abstract:

These new 31 ice deposits represent an inventory of more than 10 trillion cubic meters of solid water, similar to but greater in number and volume than previously studied features near the north pole. Similar features of nitrogen ice may exist in craters on Pluto, suggesting that craters are a favorable location for the accumulation or preservation of ices throughout the Solar System. [emphasis mine]

These results are reinforced by the existence of glacial features found in numerous Martian craters at much lower latitudes, as well as the ice suspected to exist in the permanently shadowed craters on the Moon and Mercury. The processes that put the ice there on these different planets might be fundamentally different, but the results are the same: Ice accumulating within craters.

One aspect of these high latitude craters that remains somewhat unexplained is their asymmetrical distribution around the south pole, favoring the side of the planet south of Mars’ giant volcanoes. Moreover, in looking at the ice deposits within these craters the scientists found that the ice seemed to lie off-center within the craters, favoring a similar direction.

Based on the available data, the scientists theorize that the most likely cause of this asymmetric off-center pattern is wind. From their paper:

Basic physical arguments, mesoscale atmospheric models, and geomorphological observations predict deflection of winds emanating from the south pole by the Coriolis Force. Such deflection results in a general westward trend of winds (i.e., easterlies) in the south polar regions outside the [south pole cap], matching the [ice-filled crater] offsets we observe.

This correlation implies that wind is important in … formation and/or evolution [of craters with ice]. For the case where winds control [their] formation, katabatic winds may travel down the east side of crater walls and preferentially deposit ice on the west side of the crater via orographic precipitation as they flow up the west crater wall. This mechanism thus favors local accumulation of ice within craters.

I find it fascinating that the location of ice within craters on Mars might indirectly provide scientists with information about the planet’s global weather patterns. This unexpected connection highlights the need to dismiss no data or feature in trying to understand planetary formation. Unlikely things might answer our questions.

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7 comments

  • Lee S

    The thing that fascinates me is that I was taught back in the 80’s that life was impossible on anywhere else in our solar system… I argued the point, because black smokers had been discovered recently…
    I failed the module…and the “teacher” hated me.
    The same teacher told us it was futile to imagine we could ever discover if there were planets around other stars…
    My teacher was wrong, but he should have at least accepted that doctrine can change..
    I love this stuff!

  • With regard to the foregoing comment, back in approximately the 80’s Carl Sagan wrote his famous article “Life” for Encyclopaedia Britannica, wherein he argued that life — carbon-based life — from a purely chemical-bonds point of view, could possibly exist on any planet or moon extending from Mercury to Pluto. (Earthlike) life, as Sagan pointed out, requires carbon bonds which are not too strong (so they can be broken and reshaped when desired) but also not too weak (so compounds don’t just fall apart). Well, he said, such carbon bonds are available in all strengths from extremely strong to extremely weak at all those distances/temperatures from the sun.

  • With regard to the subject of this post, to compare these southern martian water-ice-inhabited craters with the already-recognized northern hemisphere high-latitude water-ice crater “mounds,” see this paper from Icarus: “Climate-driven deposition of water ice and the formation of mounds in craters in Mars’ north polar region,” Icarus 220 (2012) 174–193 [pdf].

    Concerning the asymmetrical distribution of the southern “icy” craters which you note, compare that with the distribution map of _northern_ craters bearing ice mounds — on p. 4 (p. 177) of the foregoing Icarus paper. Looking at that, I’d say their distribution is not particular symmetrical either — particularly when examined closely.

    Notice crater Korolov, for instance, choked with ice despite its low 70’s latitude — then there’s crater Louth, actually at 70 degrees latitude. Also, FYI, here’s a great shot (taken by Mars Express) of crater Korolov’s 3,848 cubic kilometers (according to the Icarus paper’s Table 1) of ice!

    One might additionally peruse the explanation(s) proffered for the existence of the sizable ice mounds placed within certain high-latitude northern-hemisphere craters, as laid out in section 4 — beginning on p. 10 (p. 183) of the Icarus paper. From the text, it appears that the only viable theory explaining the (northern martian crater) ice-mound phenomenon is (as described in section 4.5) martian “craters as cold traps.”

    See in particular the paper’s explanatory Fig. 15 — appearing on p. 17 (190).

  • Lee S

    @Michael…. I have no doubt whatsoever we will discover microbial life on Mars…. If it ever evolved to multicellular… That’s another question… ( I hope the answer/confirmation will be answered with the next generation of Mars Landers and rovers due for the next launch window.. )
    I see no reason why multicellular life could not have evolved under the ice of the Galilain moons… That will take longer to detect, and Enceladus emains an enigma.
    Titan is my favourite place so far kind of explored to find life, because it will be very different from anything that could survive on earth… But it has liquids, an energy gradient, and tides, ( big thanks to Ralph Lorenz, the go to scientist regarding Titan… He shared many of his papers with me… I love scientists that don’t mind sharing with us mortal folk!)
    I believe in my lifetime we will either find proof that life is inevitable, or that life is very rare indeed… Either result will be very thought provoking.. but I’m betting on the former option!

  • Lee S

    And to more address your comment… Carl Sagan is amongst my heroes… Cosmos instilled in me the wonder I have for space exploration, and when I grew older, his scientific work amazed me…. Especially his speculation that complex hydrocarbons could fall like rain on Titan ( I have a Titan fetish!) , Proven to be true….
    I never met the man, but she’d a tear when he passed away…

  • Lee S

    Bloody autocorrect… Excuse my typos above….

  • Lee: Ditto. E.g.: when I was a kid and young adult Sagan and Shklovsky’s Intelligent Life in the Universe was one of my absolutely favorite books.

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