NASA scientists have found that Jupiter's moon, Ganymede, holds an ocean beneath its icy crust that is deeper and has more water than all the water on Earth, leading to speculation that it could have harbored life.

Situated at a distance of 365 million to 588 million kilometers from Earth, Ganymede, the largest moon in the Solar System and one of the four Galilean moons of Jupiter, was discovered by astronomer Galileo in 1610. Following strong hints provided by the Galileo spacecraft during its exploration of Jupiter and its moons from 1995 to 2003, scientists have been suspecting the existence of water beneath Ganymede's surface.

According to results of the new study published on March 12 in the Journal of Geophysical Research: Space Physics, the scientists used NASA's Hubble Space Telescope to observe changes in the aurorae around the celestial body and uncover new evidence confirming the discovery of a massive subterranean ocean on Ganymede.

NASA describes aurorae as "ribbons of glowing, hot electrified gas" that is observed in regions around the north and south poles of Ganymede. Since aurorae are controlled by a moon or a planet's magnetic field, scientists can gain a better understanding of what exists under the crust by observing changes in their behavior.

In the latest study, the scientists discovered that Jupiter's own magnetic field interacted with that of Ganymede to create a rocking motion in the aurorae, and the motion was being reduced by magnetic friction due to the underground ocean on the moon. The scientists claim that this new technique of studying aurorae to look for signs of a liquid ocean could lead to more instances of water being discovered on bodies that exist deeper in our solar system.

Scientists have yet to learn about the exact temperature and depth of the hidden ocean found on Ganymede, but estimate it to be 100 kilometers deep, or ten times deeper than the oceans on Earth, and buried under a 150-kilometer crust comprised mainly of ice, sprinkled with rocks and dust.