GRAIL gravity map of the Moon, a new map of the moon shows its variations in gravity. If the Moon were a perfectly smooth sphere of uniform density, the gravity map would be a single, featureless color, indicating that the force of gravity at a given elevation was the same everywhere.
Images © NASA’s Goddard Goddard Space Flight Center Scientific Visualization Studio.
These print-resolution stills show the free-air gravity map developed by the Gravity Recovery and Interior Laboratory (GRAIL) mission.
Like other rocky bodies in the solar system, including Earth, the Moon has both a bumpy surface and a lumpy interior. Spacecraft in orbit around the Moon experience slight variations in gravity caused by both of these irregularities.
The free-air gravity map shows deviations from the mean, the gravity that a cue ball Moon would have. The deviations are measured in milliGals, a unit of acceleration. On the map, dark purple is at the low end of the range, at around -400 mGals, and red is at the high end near +400 mGals. Yellow denotes the mean.