12 April 2004
Today is April 12, 2004, the 43rd anniversary of the first human flight into space (Yuri Gagarin, 1961) and the 23rd anniversary of the first NASA Space Shuttle flight (Columbia, 1981). Meanwhile, on Mars, spring is in full swing in the martian northern hemisphere. With spring comes the annual defrosting of the north polar dunes. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, acquired on April 7, 2004, shows a field of small barchan (crescent-shaped) dunes covered with the remains of wintertime frost. The dark spots around the base of each dune mark the first signs of the spring thaw. The sand in these dunes is dark, like the black sand beaches of Hawaii or the dark, sandy soil of the rover, Opportunity, landing site, but in winter and spring their dark tone is obscured by bright carbon dioxide frost. This picture is located near 75.9°N, 45.3°W, and covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.