Leonard David's INSIDE OUTER SPACE

This free-air gravity map shows deviations from the mean gravity that a cueball Moon would have.
Credit: NASA’s Scientific Visualization Studio/S. Goossens et al.

A “free-air” gravity map of the Moon’s southern latitudes has been developed from data returned by NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission.

The free-air gravity map shows deviations from the mean gravity that a cueball Moon would have.

The map extends from the south pole of the Moon up to 50°S and reveals the gravity for that region in even finer detail than the global gravity maps published previously.

The image illustrates the very good correlation between the gravity map and topographic features such as peaks and craters, as well as the mass concentration lying beneath the large Schrödinger basin in the center of the frame.

The terrain in the image is based on NASA’s Lunar Reconnaissance Orbiter (LRO) altimeter and camera data.

The view is south-up, with the south pole near the horizon in the upper left and the crescent Earth in the distance. The terminator crosses the eastern rim of the Schrödinger basin. Gravity is painted onto the areas that are in or near the night side. Red corresponds to mass excesses and blue to mass deficits.

Launched as GRAIL A and GRAIL B in September 2011, the probes — renamed Ebb and Flow — operated in a nearly circular orbit near the poles of the Moon at an altitude of about 34 miles (55 kilometers) until their mission ended in December 2012.

The distance between the twin probes changed slightly as they flew over areas of greater and lesser gravity caused by visible features, such as mountains and craters, and by masses hidden beneath the lunar surface.