Mars
Shades and textures
A Piece of Mars: This 480x270 m (0.3x0.17 mi) scene shows the contact between two very different terrains. On the left is a bright surface with polygonal cracks (characteristic of periglacial terrain - this is at a high latitude). On the right is a dark rippled sand sheet that superposes the polygonally-cracked surface. The long meandering furrows might be the beginnings of polygonal cracking in the sand, which might expand if wind doesn't erase them. (HiRISE PSP_006473_1125, NASA/JPL/Univ. of Arizona) read more ❯
Debunking Hoagland's "Glass Worms" with HiRISE
A piece of Mars: Several years ago, a guy named Richard Hoagland claimed that some parallel linear features on Mars looked like the ridges of a transparent earthworm, calling these things "glass worms". Phil Plait debunked it nicely, but Hoagland stood his ground. He hasn't said much about them lately, has he? Here's why. New images show that, as scientists originally thought, these are nothing more than windblown ripples in the floors of channels, just like the many thousands of ripples seen all over Mars. Go science! (HiRISE ESP_035634_2160, NASA/JPL/Univ. of Arizona) read more ❯
A mighty wind
A piece of Mars: I just adore that the wind can do this to a landscape. Over a long period of time, two different winds have scratched deep grooves in a rocky surface. Wind-carved rocks like this are called "yardangs". We have them in some deserts on Earth, too, but I've never seen two overlapping directions like this on Earth. Why are they more prominent on Mars? Mars has no oceans, no rivers, no beaches, no snowfall and no rain to change the surface, so the wind plays a stronger role in shaping the landscape. (HiRISE ESP_028200_1810) read more ❯
Oh, gravity, the things you can do
A piece of Mars: Steep slopes in some parts of Mars are prone to very thin landslides that leave behind dark tracks. The landslides may be triggered by the wind or nearby impacts. They always move downslope -- in this case from upper left to lower right, meandering around craters and lapping up against old, stabilized dunes. The darkest one here is brand new, having formed sometime between 2007 and 2012. (HiRISE ESP_028642_1800) read more ❯