astronomy
This is a color-enhanced photo of the plains near the south pole of Mars, in spring. Water ice and carbon dioxide ice - 'dry ice' - are both active in this landscape.
Water ice frozen in the soil splits the ground into polygons. In the spring, frozen carbon dioxide below the surface turns into gas and shoots out through vents here and there. The gas carries along fine particles that drop to the surface in dark fan-shaped deposits.
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astronomy
This picture was taken at latitude -85.044° and longitude 259.017° by the HiRISE satellite, and is available here in many formats, where you can read a bit more about it:
https://www.uahirise.org/ESP_073471_0950
It isn't natural color, as seen by normal human eyes, because the infrared, red, and blue-green channels are displayed in red, green, and blue colors.
In this article:
https://johncarlosbaez.wordpress.com/2012/11/11/wind-and-water-on-mars/
I explain the picture below, of vents on Martian dunes near the north pole.
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astronomy
@johncarlosbaez that blog post is a true joy to read and look at.
@imdef - thanks!
But we should really thank Mars for being such an interesting planet! I wanted to counteract the impression one sometimes gets that it's a dead world. Most spacecraft landing on the planet deliberately choose a flat, safe spot... not something like this: