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> Seasonal changes in Mars' North Polar Ice Cap

Seasonal changes in Mars' North Polar Ice Cap

author: Nasa/Novapix

reference: a-mar02-00002

Image Size 300 DPI: 22 * 13 cm

These images, which seem to have been taken while NASA's Hubble Space Telescope (HST) was looking directly down on the Martian North Pole, were actually created by assembling mosaics of three sets of images taken by HST in October, 1996 and in January and March, 1997 and projecting them to appear as they would if seen from above the pole. This series of pictures captures the seasonal retreat of Mars' north polar cap. October 1996 (early spring in the Northern hemisphere): in this map, assembled from images obtained between Oct. 8 and 15, the cap extends down to 60 degrees N latitude, nearly it's maximum winter extent. January 1997 (mid-spring): increased warming as spring progresses in the northern hemisphere has sublimated the carbon dioxide ice and frost below 70 degrees north latitude. The faint darker circle inside the cap boundary marks the location of circumpolar sand dunes; these dark dunes are warmed more by solar heating than are the brighter surroundings, so the surface frost sublimates from the dunes earlier than from the neighboring areas. Particularly evident is the marked hexagonal shape of the polar cap at this season. This map was assembled from WFPC2 images obtained between Dec. 30, 1996 and Jan. 4, 1997. March 30, 1997 (early summer): The cap has fully retreated to its remnant core of water-ice. This residual cap is actually almost cut into two by a large, horn-shaped canyon called Chasma Borealis which is cut deeply into the polar terrain. The HST images also reveal a curious layered terrain which is evidence of past climatic changes on Mars. The sublimation of all of the carbon dioxide has exposed the ring of dark sand dunes which encircle the North Polar Cap. Outliers of ice persist south of the polar sand sea (between the 3 o'clock and 9 o'clock positions). The bright circular features at 3, 6, and 9 o'clock are ice-filled craters.

Keywords for this photo:

1996 - 1997 - ASTRONOMY - HST - HUBBLE SPACE TELESCOPE - MARS - NORTH POLE - PLANET - POLE - SEASON -