NASA researchers refine measurement of Earth's seasonal center-of-mass shift

By the Everything Space news desk · 16 Sep 2026 · written from the sources below

Image: Phys.org

A new satellite-tracking method shows Earth's mass center wobbles half as much as previously thought, improving precision for navigation and mapping systems.

Earth's center of mass moves slightly each year as water, ice and air redistribute across the seasons, and a team led by NASA's Jet Propulsion Laboratory has developed a more precise way to measure that motion. The findings, published in Geophysical Journal International, suggest the annual swing is about half as large as earlier estimates indicated.

Because satellites orbit around Earth's true center of mass rather than its geometric center, tracking subtle shifts in satellite-to-ground-station distances can reveal how that center moves over time. The new approach combines laser tracking from dedicated geodetic satellites with GPS data and orbital measurements from additional low-Earth-orbit satellites, while also accounting for how the weight of water and ice bends the crust beneath tracking stations.

Previous international estimates from 2017 and 2023 disagreed by an amount nearly as large as the motion being measured, underscoring how difficult it has been to pin down. The revised technique aims to narrow that uncertainty by drawing on a broader, more evenly distributed set of satellite targets.

Seasonal snow buildup across North America and Eurasia pulls Earth's center of mass toward the North Pole each March, while heavy rainfall in the Amazon basin shifts it toward South America the following month. Monsoon rains in Southeast Asia add to the pattern later in the year, and swelling oceans, especially the vast Pacific, pull the center toward the South Pacific in late summer and early autumn.

Atmospheric density changes also play a role, with cold winter air over regions such as Arabia, Asia and northern Africa around the December solstice, and over South America and southern Africa around the June solstice, contributing to the oscillation.

The team's calculations align with independent gravity measurements from the GRACE-FO satellite mission, which tracks monthly shifts in Earth's gravitational field caused by moving water. Researchers say better knowledge of these small shifts can support more accurate satellite positioning systems used in mapping, navigation, shipping and agriculture.

Written in Everything Space’s own words by our news-desk model from the sources above, and checked against them in code: every number in this report appears in its sources, and no sentence is copied from them.