In early January 2005, on the 339th martian day (each day is a “sol”) of its mission, the Mars Exploration Rover (MER) Opportunity discovered a nickel-iron meteorite on the surface of Mars’ Meridiani Planum. It was the first meteorite found on another planet. Because the meteorite lies near the rover’s discarded heat shield, the MER team dubbed it Heat Shield Rock. (Its formal name is “Meridiani Planum,” but many scientists use its informal name.)
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