| dethalternate | Date: Friday, 20-March-2015, 4:48 PM | Message # 1 |
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An artist's impression showing Jupiter, and the moon Ganymede with its auroral lights
There is further, compelling evidence that Ganymede - the largest moon in the Solar System - has an ocean of water beneath its icy crust.
The new data comes from the Hubble Space Telescope, which has been studying how auroral lights dance around the satellite of Jupiter.
The presence of a sub-surface ocean would heighten interest in Ganymede as a potentially habitable world.
Europe's robotic Juice probe is being sent to orbit the moon in the 2030s.
Nasa's Galileo mission returned information in the early 2000s that suggested the 5,300km-wide moon had a hidden sea. The new insights from Hubble deepen that impression.
Damping effect
Ganymede's great distinction among moons - apart from its size - is that it has its own magnetic field.
Hubble has managed to track that field's behaviour by watching how it draws in and excites space particles, generating a glow of ultraviolet light around the satellite's north and south poles.
But this intrinsic magnetic field also interweaves with Jupiter's, and the aurora "rock" back and forth as a result of the interplay.
It is by modelling the expected rocking against what is observed by Hubble that scientists can infer something about the internal structure of the moon. And they now say a salty ocean at depth is the best explanation for what they see.
That is because Jupiter's field induces a secondary field in the salt water, and this tries to counterbalance the big planet's influence.
The end result is that the aurora rock only by two degrees over time when without the presence of the ocean, they should be rocking by six degrees
Read more/full article/source - http://www.bbc.com/news/science-environment-31855395
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