NASA tracks Earth’s shifting center
The center of mass shifts by several millimeters relative to Earth’s geometric center as enormous surface loads move between regions. Although tiny, these changes matter because the point serves as a reference for satellite navigation and measurements of surface elevation.
Researchers led by NASA’s Jet Propulsion Laboratory described their approach in a study published in Geophysical Journal International.
The method combines laser measurements from the LAGEOS satellites with GPS tracking and orbital data from satellites closer to Earth. It also accounts for the way water and ice deform the crust, moving the ground stations used to track spacecraft.
The team estimates that the annual movement is about half the size scientists believed eight years ago.
“Our findings suggest that the mass of Earth’s water and air moving between the hemisphere is smaller than previously thought,” lead researcher Donald Argus said in NASA’s report.
Snow accumulation across North America and Eurasia peaks in March, shifting the center of mass roughly 3 millimeters toward the North Pole. In April, rainwater in the Amazon basin reaches about 2,400 gigatons, pulling it 2.2 millimeters toward South America.
Between August and October, rainfall and meltwater increase ocean mass, shifting the balance toward the South Pacific. Dense winter air contributes further seasonal changes.
The findings agree with observations from the GRACE Follow-On mission, whose twin satellites measure changes in Earth’s gravity as water moves above and below ground.
“While these movements might appear tiny, our modern world relies on extremely accurate positioning measurements,” study coauthor Felix Landerer said.
Better tracking could improve mapping and navigation, with applications ranging from global shipping to precision agriculture.
Earlier, Qazinform News Agency reported that a section of eastern Africa has reached a more advanced stage of continental separation than previously thought, potentially paving the way for a new ocean in the distant future, according to a study published in Nature Communications.
