CANADA: Astronomers have found the most conclusive evidence yet that a large watery ocean lies beneath the surface of Jupiter’s moon Ganymede.
Scientists have suspected for decades that a subterranean ocean might slosh between the rocky mantle and icy crust of the largest moon in our solar system, but they had not been able to prove it definitively until now.
Using the Hubble Telescope, a team of researchers has detected slight fluctuations in two bands of glowing auroras in Ganymede’s atmosphere that they say could occur only if the moon contained a salty body of water.
“The Solar System is now looking like a pretty soggy place,” said Jim Green, director of planetary science at NASA. “The more we look at individual moons, the more we see that water is really in enormous abundance.”
Ganymede is the only moon in the Solar System that has its own magnetic field. However, it is also affected by the magnetic field of Jupiter, the giant planet next door.
The effect of Jupiter’s magnetic field on Ganymede changes every 10 hours, which is the length of time it takes the planet to make a full rotation on its axis. For five hours its magnetic field points toward Ganymede, then for another five hours it points away.
“It’s like a lighthouse,” said Joachim Saur of the University of Cologne in Germany, who led the research.
Saur figured that these regular shifts in Jupiter’s magnetic field would affect the position of the auroras in Ganymede’s atmosphere differently depending on whether or not the moon has a subsurface ocean.
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