This graphic shows the projected paths into the moon by spacecraft Ebb and Flow. / AP
Twin NASA spacecraft smacked into a mountain on the moon Monday at 3,760 mph, ending a mission measuring lunar gravity. The space agency will name the mountainside landing spot for the probes after the late astronaut Sally Ride, who was part of the mission's science team.
The Gravity Recovery and Interior Laboratory (GRAIL) mission probes, called Ebb and Flow, flew in formation over the lunar surface to map its gravity from an altitude of 34 miles. The planned impact capped a mission that found hardened veins of magma buried in the moon's thinner-than-expected crust.
The $496 million probes provided the most exacting map of lunar gravity yet made, says Charles Elachi of NASA's Jet Propulsion Laboratory in Pasadena, Calif. The findings offer clues to the moon's composition and could aid future landing attempts.
Data from the impact will serve as an experimental check on engineers' estimates of flight times of lunar orbiters without fuel. With the fuel on the probes exhausted, mission controllers aimed the probes for impact on a mountain ridge near Goldschmidt crater, far from any of the 23 Russian and U.S. lunar landing sites. "We picked this landing site so we would not hit any historical sites," says GRAIL project manager Dave Lehman.
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