NASA shows unprecedented map of Earth's geoid

NASA has unveiled a striking three-dimensional map of Earth's gravitational field, a representation known as a geoid. This visualization, derived from extensive satellite observations, highlights the planet's uneven gravitational pull, a characteristic less symmetrical than commonly imagined.

The geoid illustrates equipotential surfaces, depicting the hypothetical sea level if oceans were still. It accounts for the mass of subterranean materials like rocks, magma, and water. Specialists clarified that the graphic is not a photograph of Earth's exterior but an illustration that exaggerates the vertical scale by 7,000 to 10,000 times to make subtle gravitational differences visible.

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Because the distribution of materials in the Earth's interior varies, its gravity field has hills and valleys.

"Because the distribution of materials in the Earth's interior varies, its gravity field has hills and valleys," explained Michael Watkins, a scientist at NASA's Jet Propulsion Laboratory (JPL), in a 2020 study. Areas with higher mass concentration, such as the Andes or Himalayas, exhibit stronger gravitational pull, depicted in red. Conversely, regions with lower density, like the Indian Ocean or Congo River basin, appear in blue.

To create this detailed map, technical teams processed over a billion observations collected over 15 years by 19 satellites. The global model GOCO06s integrated data from the European Space Agency's (ESA) GOCE mission and the GRACE program, a joint effort by NASA and the German Aerospace Center. The map also reveals geoid height variations, ranging from a maximum of 85 meters in Iceland to a minimum of 106 meters below mean sea level in southern India. This tool aids in analyzing the water cycle, groundwater resources for agriculture, and long-term sea-level rise.

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It is very difficult to measure how much water there is deep in the ground and how much it changes from year to year.