Changes in Earth’s gravity field resulting from the earthquake that hit Japan on 11 March 2011 (mE=10-12s-2). A combination of data from ESA’s GOCE mission and the NASA–German Grace satellite, shows the ‘vertical gravity gradient change’. The 'beachball' marks the epicenter.
Variations in total water storage from normal, in millimeters, in the Tigris and Euphrates river basins, as measured by NASA's Gravity Recovery and Climate Experiment (GRACE) satellites, from January 2003 through December 2009. Reds represent drier conditions, while blues represent wetter conditions. The majority of the water lost was due to reductions in groundwater caused by human activities. By periodically measuring gravity regionally, GRACE tells scientists how much water storage changes over time.
Before the launch of NASA's Gravity Recovery and Climate Experiment (GRACE) in 2002, scientists' knowledge of Earth's gravity field was based upon decades of data from geodetic satellites (left image). GRACE has allowed monthly gravity measurements that are more than 100 times more accurate than these previous models, permitting scientists to characterize how Earth's gravity field varies over time and space, as illustrated by the map on the right, produced after just 13 months of GRACE data.
