CHRYSE PLANITIA

Sunlit half of Mars, as seen by the Mars Global Surveyor spacecraft. The dark areas indicate 1/4 Chryse Planitia, Mars, seen from the Viking 1 lander. region of the planet Mars that includes the landing site of the U.S. Viking 1 planetary probe. The Viking 1 lander, which touched down at 22.48 N and 47.97 W in 1976, revealed that Chryse Planitia is a rolling, boulder-strewn plain, with scattered dusty dunes and outcrops of bedrock. The rocks are believed to be eroded remnants of basaltic lavas. Analysis of the dusty soil by Viking probe instruments showed the principal constituent materials by weight as silica (44 percent), ferric oxide (18 percent), magnesium oxide (8 percent), sulfur trioxide (8 percent), alumina (6 percent), and calcium oxide (6 percent). This composition is consistent with igneous rocks formed from magmas that interacted with subsurface ice. The rocks were later affected by weathering and leaching processes that stained their surfaces with reddish iron-oxide minerals and concentrated certain sulfates (and possibly carbonates) in the surface soil.