Jupiter moon Ganymede could have ocean with more water than Earth
- March 25, 2015
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A moon of Jupiter may conceal under its icy surface an ocean with more water than all of that on Earth's surface, new findings suggest.
Scientists used NASA's Hubble Space Telescope to investigate Ganymede, the Solar System's largest moon-about one-and-a-half times wider than ours.
Ganymede is also the only moon with its own magnetic field. The magnetic field causes aurorae, which are ribbons of glowing, hot electrified gas, in areas circling the north and south poles.
But Ganymede is also embedded in Jupiter's magnetic field. When Jupiter's magnetic field changes, the aurorae on Ganymede also change, “rocking” back and forth, scientists explain.
The thinking behind the study is that if a saltwater ocean were there, Jupiter's magnetic field would create a secondary magnetic field in that ocean. This secondary field would counter Jupiter's own-and as a result, suppress the rocking of the aurorae.
This suppression indeed happens, and so strongly that it reduces the rocking of the aurorae by some two-thirds, the investigators calculated. As a result, they estimate the ocean is 60 miles (100 kilometers) thick - 10 times deeper than Earth's oceans - and is buried under a 95-mile (150-kilometer) crust of mostly ice.
Scientists led by Joachim Saur of the University of Cologne in Germany came up with the idea of using Hubble to learn more about the inside of the moon.
“I was always brainstorming how we could use a telescope in other ways,” said Saur. “Is there a way you could use a telescope to look inside a planetary body? Then I thought, the aurorae! Because aurorae are controlled by the magnetic field, if you observe the aurorae in an appropriate way, you learn something about the magnetic field. If you know the magnetic field, then you know something about the moon's interior.”
The findings were published online in the Journal of Geophysical Research: Space Physics on March 12.
Source : world-science.net