Ganymede: oceans on Jupiter’s moon could have been home to alien life

While scientists have long suspected that there was water beneath the surface — ever since the Galileo spacecraft provided hints during its exploration of the planet and its moons from 1995 to 2003 — Nasa scientists have confirmed the theory using new data.

"It is one step further toward finding that habitable, water-rich environment in our solar system," said astronomer Heidi Hammel with the Washington-based Association of Universities for Research in Astronomy. It is the latest indication that many of the objects in our solar system have water and could support life — earlier this week, scientists confirmed that Saturn’s moon has hot springs underneath its crust.

To find the discovery, scientists had to work backwards from the visuals seen on the planet.

Like Earth, Ganymede has a liquid iron core that generates a magnetic field, though Ganymede's field is embedded within Jupiter's magnetic field. That sets up an interesting dynamic with telltale visuals - twin bands of glowing aurora around Ganymede's northern and southern polar regions.

As Jupiter rotates, its magnetic field shifts, causing Ganymede's aurora to rock. Scientists measured the motion and found it fell short. Using computer models, they realized that a salty, electrically conductive ocean beneath the moon's surface was counteracting Jupiter's magnetic pull.

Scientists used over 100 computer models to understand whether the aurora could be affected by anything else, and repeated many of the observations. After that, scientists were confident that what they had seen indicate the sub-ice water.

"They developed new approach to look inside a planetary body with a telescope," said NASA planetary science division director Jim Green

Additional reporting by Reuters