Satellite measurements offer scientists a new view of our planet.
Of the terrestrial planets in the solar system, Earth is not only the largest body but also the most massive. A calculation of its weight puts it slightly over 6.58 sextillion tons (that's 6.58x10^21 or 6,580,000,000,000,000,000,000). It's heavy because everything on our planet has mass—from the land that covers the continents to the water that fills the oceans. Earth's mass, however, isn't distributed evenly. Varying surface topography and the continuous movement of water cause different parts of the globe to have more or less mass than other regions. Since 2002, NASA's twin GRACE satellites have mapped Earth's gravity (the attractive force exerted by its mass), enabling scientists to see these differences and monitor how they change over time. Watch the visualization for a tour of Earth's gravity field.