Robby
03-03-2008, 03:42 PM
http://antwrp.gsfc.nasa.gov/apod/image/0803/dunes2_hirise.jpg (http://antwrp.gsfc.nasa.gov/apod/image/0803/dunes2_hirise_big.jpg)
Sand Dunes Thawing on Mars
Credit: HiRISE (http://hirise.lpl.arizona.edu/), MRO (http://mars.jpl.nasa.gov/mro/), LPL (U. Arizona) (http://wwwvims.lpl.arizona.edu/), NASA (http://www.nasa.gov/)
Explanation: What are these strange shapes on Mars? Defrosting sand dunes. As spring now dawns on the Northern Hemisphere of Mars, dunes of sand near the pole, as pictured above (http://hirise.lpl.arizona.edu/PSP_007043_2650), are beginning to thaw. The carbon dioxide (http://en.wikipedia.org/wiki/Carbon_dioxide) and water ice (http://antwrp.gsfc.nasa.gov/apod/ap050720.html) actually sublime (http://www.youtube.com/watch?v=J8mDGwf-5x0) in the thin atmosphere directly to gas. Thinner regions of ice typically defrost (http://www.ehow.com/how_2064543_defrost-freezer.html) first revealing sand whose darkness soaks in sunlight and accelerates the thaw (http://www.youtube.com/watch?v=q6YxRjqkqLY). The process might even involve sandy jets exploding (http://antwrp.gsfc.nasa.gov/apod/ap060823.html) through the thinning ice. By summer, spots (http://antwrp.gsfc.nasa.gov/apod/ap040831.html) will expand to encompass the entire dunes. The Martian North Pole (http://antwrp.gsfc.nasa.gov/apod/ap981216.html) is ringed by many similar fields of barchan sand dunes (http://en.wikipedia.org/wiki/Barchan), whose strange, smooth arcs are shaped by persistent Martian winds (http://antwrp.gsfc.nasa.gov/apod/ap990112.html).
(Via NASA (http://antwrp.gsfc.nasa.gov/apod/ap080303.html))
Sand Dunes Thawing on Mars
Credit: HiRISE (http://hirise.lpl.arizona.edu/), MRO (http://mars.jpl.nasa.gov/mro/), LPL (U. Arizona) (http://wwwvims.lpl.arizona.edu/), NASA (http://www.nasa.gov/)
Explanation: What are these strange shapes on Mars? Defrosting sand dunes. As spring now dawns on the Northern Hemisphere of Mars, dunes of sand near the pole, as pictured above (http://hirise.lpl.arizona.edu/PSP_007043_2650), are beginning to thaw. The carbon dioxide (http://en.wikipedia.org/wiki/Carbon_dioxide) and water ice (http://antwrp.gsfc.nasa.gov/apod/ap050720.html) actually sublime (http://www.youtube.com/watch?v=J8mDGwf-5x0) in the thin atmosphere directly to gas. Thinner regions of ice typically defrost (http://www.ehow.com/how_2064543_defrost-freezer.html) first revealing sand whose darkness soaks in sunlight and accelerates the thaw (http://www.youtube.com/watch?v=q6YxRjqkqLY). The process might even involve sandy jets exploding (http://antwrp.gsfc.nasa.gov/apod/ap060823.html) through the thinning ice. By summer, spots (http://antwrp.gsfc.nasa.gov/apod/ap040831.html) will expand to encompass the entire dunes. The Martian North Pole (http://antwrp.gsfc.nasa.gov/apod/ap981216.html) is ringed by many similar fields of barchan sand dunes (http://en.wikipedia.org/wiki/Barchan), whose strange, smooth arcs are shaped by persistent Martian winds (http://antwrp.gsfc.nasa.gov/apod/ap990112.html).
(Via NASA (http://antwrp.gsfc.nasa.gov/apod/ap080303.html))