Science in Mind

A moon mission ends with a plume of dust

In December, scientists bid a fond farewell to the MIT-led GRAIL mission, which provided the highest-resolution gravity map yet of the moon—or any planetary body. The twin washing machine-sized spacecraft, called Ebb and Flow, had circled the moon in tandem, gathering data for months, before ending their mission by crash landing near the southern slope of an unnamed mountain.

Because the area where they crashed was in shadow, there was no video footage of Ebb and Flow’s final moments. Their legacy would be the data, which is still being analyzed. A first analysis has already revealed one surprise: the moon’s crust was more fractured than anyone had previously thought.

Now, NASA has posted a series of images that are the equivalent of the final resting spots of the “robotic twins,” as they’ve been called by MIT geoscientist Maria Zuber. The spacecraft crashed in an area that was in shadow, but the dust plume they ejected was carefully monitored by another spacecraft, called the Lunar Reconaissance Orbiter.

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Here, the camera shows the impact site of the Ebb spacecraft. The Lunar Reconaissance Orbiter’s instruments detected a chemical signature in the dust released by the crash, including mercury and atomic hydrogen. The observations are similar to what scientists observed when a different spacecraft, called LCROSS, smashed into the moon in 2009.

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