5. The Holy GRAIL of Lunar Gravity Mapping
The GRAIL mission comprised twin spacecraft – with two of the best names in recent memory, Ebb and Flow – tasked with mapping the Moon’s gravitational field and internal structure. The orbiters acquired data for nearly 12 months, producing beautiful detailed maps of surface and subsurface features. In the Bouguer gravity anomaly map above, contributions from surface features like mountains and valleys are removed; results indicate variations in crustal thickness or rock density. Based on this latest mine of data, the GRAIL team has shown that a very thin veneer of crust underlies some of the largest impact basins like Crisium and Moscoviense. On December 17th, Ebb and Flow enacted a kamikaze maneuver, crashing into the surface near the north Lunar pole and conducting a final experiment on the surface’s properties in the process.
Image: Maps of the moon's Bouguer gravity anomalies as measured by NASA's GRAIL mission. (Credit: NASA / JPL / GSFC / MIT)