The twin GRAIL spacecraft will impact the moon’s surface on December 17, 2012

The two Gravity Recovery and Interior Laboratory (GRAIL) spacecrafts, Ebb and Flow, are running out of fuel after being in lunar orbit since January 2012. They will be commanded to crash into the rim of an unnamed crater near the Moon’s north pole at speed of 1.7 km/s (3,760 mph) on December 17 at 19:28 UTC. GRAIL spacecraft were originally tasked with 90-day science missions, which ran from March to May, but NASA extended mission, allowing the two probes to gather a trove of additional data.

Maps of Earth’s moon highlight the region where the twin spacecraft of NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission will impact  (Credit: NASA/GSFC)

Ebb spacecraft will undergo a controlled impact slamming into a 2 km high rim of a crater that has been buried in ejecta near north pole of the Moon and Flow spacecraft will impact about 30 seconds later, about 40 apart. About 54 minutes before impact, they’ll burn the remaining fuel to complete the last maneuver.

Unfortunately, the impact region will be shadowed at the time so there will be no imagery provided.

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