GRAIL Primary Mission Gravity Maps (AGU 2012)
- Visualizations by:
- Ernie Wright
- View full credits
If the Moon were a perfectly smooth sphere of uniform density, the gravity experienced by the spacecraft would be exactly the same everywhere. But like other rocky bodies in the solar system, including the Earth, the Moon has both a bumpy surface and a lumpy interior. As the spacecraft fly in their orbits, they experience slight variations in gravity caused by both of these irregularities, variations which show up as small changes in the separation of the two spacecraft.
The free-air gravity map shows these variations directly. (
Free-airis a historical term; there is, of course, no air on the Moon.) The Bouguer gravity map subtracts the effect of the bumpy surface to show the lumpiness underneath. The elevation maps from the laser altimeter on Lunar Reconnaissance Orbiter (LRO) were used to create a model of what the gravity would be if the Moon were bumpy but not lumpy. This model was then subtracted from the free-air map to produce the Bouguer map. (Note: The Bouguer map shown here was filtered to emphasize smaller features; harmonic degrees 1 to 6 were excluded.)
The crustal thickness map is inferred from the Bouguer map: If the density of the crust is assumed to be uniform, then the gravity anomalies visible in the Bouguer gravity map can be explained by variations in the thickness of the crust. Highs in gravity indicate places where the denser mantle is closer to the surface, and hence where the crust is thinner.
While aiding navigation for future lunar missions, GRAIL's gravity measurements reveal information about the internal structure of the Moon, improving our understanding of the origin and development of not just the Moon, but also the Earth and the rest of the inner solar system.
Side-by-side rotating Moon globes showing LOLA elevation and GRAIL free-air gravity.
This video is also available on our YouTube channel.

Moon free-air gravity maps in a cylindrical projection suitable for spherical texture mapping. Centered at 0° longitude. Includes shaded relief of surface features. Versions of the map are provided which either include or omit lower harmonic degrees corresponding to large features in the gravity field.

Moon Bouguer gravity maps in a cylindrical projection suitable for spherical texture mapping. Centered at 0° longitude. Includes shaded relief of surface features. Versions of the map are provided which either include or omit lower harmonic degrees corresponding to large features in the gravity field.
For More Information
See http://www.nasa.gov/home/hqnews/2012/dec/HQ_12-417_GRAIL.html
Credits
Please give credit for this item to:
NASA's Goddard Space Flight Center Scientific Visualization Studio
Animator
- Ernie Wright (USRA) [Lead]
Scientists
- Erwan M. Mazarico (NASA/GSFC)
- Maria Zuber (Massachusetts Institute of Technology)
Papers
This visualization is based on the following papers:- M. T. Zuber et al., Gravity field of the Moon from the Gravity Recovery and Interior Laboratory (GRAIL), Science 10.1126/science.1231507 (Dec. 5, 2012)
Missions
This visualization is related to the following missions:Series
This visualization can be found in the following series:Datasets used in this visualization
GRAIL GRAIL Bouguer Gravity (A.K.A. Bouguer Gravity) (Collected with the Lunar Gravity Ranging System sensor)
GRAIL GRAIL Crustal Thickness (A.K.A. Crustal Thickness) (Collected with the Lunar Gravity Ranging System sensor)
LRO DEM (A.K.A. Digital Elevation Map) (Collected with the LOLA sensor)
GRAIL GRAIL Free-Air Gravity (A.K.A. Free-Air Gravity) (Collected with the Lunar Gravity Ranging System sensor)
Note: While we identify the data sets used in these visualizations, we do not store any further details nor the data sets themselves on our site.