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Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →NASA’s September 16, 2026 report describes a seasonal shift of a few millimeters in Earth’s center of mass, not movement of the solid core. Water, ice and air move around the planet, changing where its mass is concentrated relative to Earth’s geometric center. A new satellite-tracking method puts the annual back-and-forth motion at about half the size researchers estimated eight years earlier.
What NASA means by “Earth’s center”
Earth has more than one meaningful center. Its geometric center is the center of the planet’s shape; its center of mass, also called the geocenter, is the balance point of all its mass. As water, ice and air shift from place to place, the geocenter shifts slightly relative to the geometric center.
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NASA’s report concerns that millimeter-scale seasonal change. It does not describe the planet’s solid core moving, nor does it report a change in Earth’s orbit.
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Satellites orbit in response to Earth’s gravity, which reflects the distribution of mass on and within the planet. Changes in the distances between satellites and ground stations can therefore reveal changes in the geocenter. NASA says the new approach combines GPS tracking and orbital information from multiple low Earth orbit satellites with satellite laser ranging.
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The method also accounts for a complication in the measurements: water and ice loading deform Earth’s crust, carrying the ground stations used for observations with it. Earlier satellite laser-ranging estimates were limited by the uneven global distribution of ranging stations. NASA says broadening the satellite observations and modeling crustal deformation help reduce uncertainty.
The technique was developed by Donald Argus and colleagues at NASA’s Jet Propulsion Laboratory, the University of Nevada, the University of Montana and Germany’s Helmholtz Centre for Geosciences. NASA reports that its calculations agree with observations from GRACE-FO, whose twin satellites track monthly changes in Earth’s gravity, primarily as water moves above and below ground. Their separation changes slightly as they travel through variations in gravity. GRACE-FO is a partnership with Germany’s GFZ.
Why the estimate is smaller than earlier estimates
NASA says international estimates from 2017 and 2023 differed by 7 millimeters (0.27 inches)—nearly as large as the motion being estimated. Argus told NASA that the new estimate of the yearly movement is about half what researchers believed eight years earlier. The report does not give one headline amplitude for the annual motion.
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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minuteThe revision is not evidence that Earth’s mass suddenly changed. It reflects a new way of estimating the geocenter’s movement, designed to address limitations in earlier observations and account for motion of the crust beneath observing stations.
What shifts the geocenter through the year
NASA groups the drivers into continental water, oceans and atmosphere. Continental water includes snow and ice, lakes and rivers, soil moisture and groundwater. The seasonal pattern reflects mass moving among regions, not a single source acting alone.
| Seasonal example | NASA’s reported effect |
|---|---|
| March snow | Snow accumulation in North America and Eurasia is at a maximum and shifts the geocenter about 3 millimeters toward the North Pole. |
| April Amazon rainfall | Rainwater in the Amazon River basin peaks at 2,400 gigatons and shifts the geocenter 2.2 millimeters toward South America. |
| August–October ocean mass | Meltwater and rain increase ocean mass, shifting the geocenter toward the South Pacific. NASA says this large Pacific mass change outweighs changes in other oceans. |
| November Southeast Asian monsoon | Monsoon water reaches a maximum of 600 gigatons and contributes slightly to the annual oscillation. |
| Around December 21 and June 21 atmospheric mass | Cold, dense winter air affects the mass balance over Arabia, Asia and northern Africa around December 21, and over South America and South Africa around June 21. |
These are examples of how regional seasonal changes contribute to the overall movement; they are not a complete accounting of every component of the annual shift.
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Why a few millimeters matter
The geocenter is an important reference for satellite navigation and elevation measurements. When scientists and engineers measure positions or map elevations, they need a stable, precise reference system. Understanding how Earth’s mass changes that reference helps improve systems used in mapping and navigation. As JPL study coauthor Felix Landerer explained to NASA, precise positioning supports applications from global shipping logistics to precision agriculture.
NASA’s visualization accompanying the report shows geocenter motion from 1993 to 2017; that display period should not be confused with the observation interval of the new method.
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Sources
- NASA Jet Propulsion Laboratory, “NASA Watches Earth’s Weight, Finds Center of Mass” (September 16, 2026)
- NASA Goddard Space Flight Center, “Satellite Laser Ranging (SLR)” (updated September 30, 2026)
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