NASA scientists have found strong evidence of a saltwater ocean under the icy surface of Ganymede, Jupiter’s largest moon. The discovery suggests that Ganymede could potentially support life as we know it. Using data from the Hubble Space Telescope, NASA found that the subterranean ocean holds more water that all of the water on Earth’s surface.

Ganymede, Jupiter's Moon, Has Massive Ocean: NASA

Ganymede has long been suspected to contain water

John Grunsfeld, the assistant administrator of NASA’s Science Mission Directorate, said it was a “significant milestone.” He said the discovery of a deep ocean beneath the icy crust of Ganymede opens up “exciting possibilities for life beyond Earth.” Ganymede is the largest moon in our solar system. It is the only moon in the solar system that has its own magnetic field.

Jupiter’s largest moon has long been suspected to contain water. Researchers first suspected the presence of the ocean on Ganymede in 1970. In 2002, NASA’s Galileo mission provided the first evidence supporting these assumptions. Now, Hubble Space Telescope has found compelling evidence. Scientists believe that its ocean is buried under a 95-mile crust of ice. Ganymede’s saltwater ocean is 60 miles thick, almost 10 times deeper than the Earth’s oceans.

How NASA determined the presence of water

Ganymede’s magnetic field creates ribbons of glowing, hot electrified gas, called aurorae, in regions circling the north and south poles of the moon. The moon is pretty close to Jupiter, so it’s also embedded in Jupiter’s magnetic field. The aurorae on Ganymede change, rocking back and forth, when Jupiter’s magnetic field changes.

The changes in aurorae helped scientists determine that there was a massive saltwater ocean under Ganymede’s crust, affecting its magnetic field. In the presence of a saltwater ocean, Jupiter’s magnetic field creates a secondary magnetic field in the ocean that counter’s Jupiter’s magnetic field. This “magnetic friction” significantly suppresses the rocking of the aurorae.

Scientists said Ganymede’s ocean fights Jupiter’s magnetic field so strongly that the rocking of the aurorae is reduced to just 2 degrees, compared to 6 degrees if the saltwater ocean were not present.