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On July 4, 1997, the Pathfinder spacecraft touched down in a northern lowland called Chryse Planitia carrying a small rover named Sojourner—as well as a large amount of stowaways in the form of earthly microbes.

The group zeroed in on a region on Mars where the highlands known as Arabia Terra bump up against the lowlands of Chryse Planitia — a place where the waters of an ancient ocean might have lapped at the shoreline.

The site, Oxia Planum, lies a few hundred kilometers southwest of Mawrth Vallis and east of the Chryse Planitia lowlands.

The surface of the planet is crossed with features that resemble old river channels, like the tributaries and canyons that lead into Chryse Planitia, the Plain of Gold, an ancient crater 1,000 miles wide and a mile-and-a-half deep.

Viking space probes arrived at the planet in 1976, Viking 1 landed in Chryse Planitia and Viking 2 in Utopia Planitia.