Researchers have used the Gravity Recovery and Climate Experiment (GRACE) satellite mission to study changes in mass on Earth, including the discovery of "gravity holes" - spots on the planet's surface with less gravity than others. GRACE, launched in 2002, mapped the planet's mass by measuring the distance between two satellites as they orbited the Earth. The mission not only revealed changes in gravity but also provided evidence of melting ice caps. The data collected by GRACE was so significant that NASA launched a follow-up mission, GRACE-FO, in 2018.
Gravity is not uniform across the Earth due to variations in mass caused by Earth's inner structure and topography. Scientists use advanced instruments and satellite data to measure these small abnormalities. The strongest gravitational forces are found in the eastern Pacific Ocean near Australia and Indonesia, resulting from plate tectonic movements. Gravity anomalies are also observed in regions such as the North American ice sheet depression and an unusual gravity hole in the Indian Ocean. Additionally, human activities, including melting polar ice caps and changes in water reservoirs, are affecting gravity. Understanding these variations is crucial for tracking climate change and water supplies.
