Here are dunes on Mars... with stands of trees on top?!? No, that's an optical illusion. In fact what you're seeing are steep slopes with dark stuff slowly sliding down them! Earlier I showed you similar things on the barchans of Mars.
In 2010 astronomer Candy Hansen explained this photo, writing:
"There is a vast region of sand dunes at high northern latitudes on Mars. In the winter, a layer of carbon dioxide ice covers the dunes, and in the spring as the sun warms the ice it evaporates. This is a very active process, and sand dislodged from the crests of the dunes cascades down, forming dark streaks."
More recently, though, scientists have suggested that geysers are involved, which would make this a very active process indeed!
For a beautiful huge picture showing this region, go here:
• HiRISE (High Resolution Imaging Science Experiments), Falling material kicks up cloud of dust on dunes, http://hirise.lpl.arizona.edu/PSP_007962_2635
and check out the choices near the bottom. Or just go here:
http://math.ucr.edu/home/baez/007962_2635.jpg
#astronomy
In 2010 astronomer Candy Hansen explained this photo, writing:
"There is a vast region of sand dunes at high northern latitudes on Mars. In the winter, a layer of carbon dioxide ice covers the dunes, and in the spring as the sun warms the ice it evaporates. This is a very active process, and sand dislodged from the crests of the dunes cascades down, forming dark streaks."
More recently, though, scientists have suggested that geysers are involved, which would make this a very active process indeed!
For a beautiful huge picture showing this region, go here:
• HiRISE (High Resolution Imaging Science Experiments), Falling material kicks up cloud of dust on dunes, http://hirise.lpl.arizona.edu/PSP_007962_2635
and check out the choices near the bottom. Or just go here:
http://math.ucr.edu/home/baez/007962_2635.jpg
#astronomy
