The weird south pole of Mars

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Mars' south pole region

Cool image time (literally)! The photo above, cropped slightly to show here, was taken by Mars Reconnaissance Orbit (MRO) in August 2016 and was released today as part of the monthly release of captioned images. And though it looks like a fractal computer-generated animation still, it is instead real, showing the strange and quite alien terrain that routinely forms at the carbon dioxide ice cap there.

The polar cap is made from carbon dioxide (dry ice), which does not occur naturally on the Earth. The circular pits are holes in this dry ice layer that expand by a few meters each Martian year. New dry ice is constantly being added to this landscape by freezing directly out of the carbon dioxide atmosphere or falling as snow. Freezing out the atmosphere like this limits how cold the surface can get to the frost point at -130 degrees Celsius (-200 F). Nowhere on Mars can ever get any colder this, making this this coolest landscape on Earth and Mars combined!

This region is about 4 degrees north of the south pole itself.



  • Dale Martin

    I was wondering how it could be 4 deg south of the south pole ?? I could understand 4 deg north….

  • Dale: It can’t. I have corrected my post. Thanks.

  • Orion314

    I Don’t understand the cold temp limit, please elaborate…

  • Orion314: Their words, not mine. However, if I had to guess, what they are saying badly is that the poles of Mars are the coldest places on that planet, and will definitely be colder than anyplace on Earth. The limit I think has to do with the freezing and evaporation of the dry ice, which as it does so will also effect the temperature as well. Think about how the evaporation of sweat will cool you off. I guess they are saying that freezing will act to limit how cold things get.

  • wayne

    Orion314/ Mr Z.:

    The article is phrased awkwardly, but yes, Mr Z , that is the answer I would put forth, as well.
    There’s a better techie-phrase that describes this process, but I can’t think of it off-hand.

    I think they mean, “…when carbon-dioxide freezes out of the atmosphere in this manner, it limits how cold the surface can get…”

    (or, I could be totally wrong…)

  • wayne

    I’m thinking ….. along the lines of— water being sprayed on orange trees, to prevent them from freezing during cold-snaps.
    There’s a certain amount of heat-energy in all that dry-ice and when it phase-shifts back-n-forth, you get heat-transfer effects.

    (I only play at being a Scientist on the interweb, but I have stayed at Holiday Inn’s before. And… Stevie Wonder always stays at Holiday Inn’s– the floor plans are all identical across Properties. Think about it…)


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