Waiting for spring

A piece of Mars: These sharp-tipped hills are dunes near the north pole of Mars. At the height of summer they’re lovely dark dunes, but because it’s just barely spring here they’re still covered in white frost (mostly CO2 ice, but a little water ice). Like penguins who huddle in the dark of the polar

How sand forms on Mars

A piece of Mars: All that sand on Mars — where does it come from? It’s often hard to figure that out. Here is a rare case where we can see material shedding from a stack of bright layered rocks, moving downslope (toward the top of the frame). (PSP_003684_1730, NASA/JPL/Univ. of Arizona)

Martian sports

A piece of Mars: In the center are two dark dunes, racing one another to jump over hurdles formed of older, now inactive dunes (or maybe those bright things are ripples, we still don’t know for sure). The dune in the lead has been slowed by this barrier, but it is starting to crawl over