A Piece of Mars: Gray dunes have migrated over reddish rock, moving toward a narrowing cleft surrounded by tall tan cliffs. Bright lines on the dunes are exposed internal layers (bones of the dunes, really) that show you where the lee-side slopes once were (so you can tell they’ve moved to the left). The cliffs are made of layered rocks (extra points if you can find the fault), suggesting these are sedimentary layers, laid down long ago in Mars’ geologic past. The whole HiRISE image is worth a long look, it’s really amazing. (HiRISE ESP_049009_1520, NASA/JPL/Univ. of Arizona)

Comments (2)

  1. I am intrigued by those bright greenish-blue holes, scattered around the dunes (most are in the lower right side of the image). What are those?!!!!! I want to jump in! I counted a dozen.

    1. I think you might be seeing boulders, not holes. The sun is shining from the upper left, so thinks that poke up (like rocks) are lit on the left side, whereas things like holes would be lit on their right side. If I’m right, then those are rocks that have eroded out from the cliffs and rolled/fallen downhill, and one day those riding martian ATV signs there will have to heed signs saying “Watch for fallen rocks”.

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