Lunar Attraction

The twin spacecraft that compiled this map of the Moon's gravitational field will end their mission on December 17 by crashing into a lunar mountain. The GRAIL mission plotted tiny differences in the Moon's gravitational pull by precisely measuring the distance between the two craft as they were pulled by different parts of the lunar surface. In this map, which is centered on the lunar farside, red indicates regions with a slightly stronger gravitational pull (because the surface material is denser), while blue indicates regions with a weaker pull. The craft are being intentionally crashed into the Moon because they have completed their mission and their fuel is almost exhausted. A controlled crash will provide additional details on the lunar gravitational field. [NASA/GSFC]