NASA will launch on Tuesday the newest GRACE (Gravity Recovery and Climate Experiment) satellites in order to measure changes in the Earth’s gravitational field with more sensitivity. They are to replace two satellites that have been unused after 16 years in orbit and provide information for understanding climate change and possibly predict earthquakes.
Why is this launch so important?
Felix Landerer, a geophysicist at NASA’s Jet Propulsion Laboratory, explained that water is the reason for the Earth’s unbalanced gravitational field. The states through which water goes along the seasons affect the soil and leaves a mark on the gravity field. This shift is only visible with the help of GRACE because the satellites will create a gravity map while flying across the field. It is stronger where there are mountains with water, snow or ice and it is weaker where the soil is drier.
Information gathered in the past few years
The gravitational field in Greenland has changed due to ice melting. The old GRACE satellites have gathered information about 4,000 gigatons of ice melted enough to flood the lower 48 states. Thus, the massive ice sheet exerts its own gravity field around the ocean by pulling the water toward itself and then diminishing when it melts or shrinks.
In late 2010, French scientists found data showing how gravitational fields around an underground rock near Japan had started to change. After a few months, the Tohoku earthquake took place and killed about 16,000 people. For eight years before Tohoku earthquake, everything was in order. It was only after the shift in gravity that it concerned the geologists.
David Jacobson, a quake geologist, said that the ability to observe such anomalies in time would have the potential to find out in advance whether a big earthquake will take place or not. However, geologists are waiting for more data from GRACE in order to decide if such signals will, in fact, predict earthquakes or not.