Evidence for ocean on Ganymede increases

[Brian G Turner]

The BBC reports that observations by the Hubble Telescope strongly suggest a deep ocean on Ganymede, one of the moons of Jupiter, and the largest moon in the solar system:
http://www.bbc.co.uk/news/science-environment-31855395

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.

 

[BAYLOR]

So life might be a possibility there?

 

[Mirannan]

So life might be a possibility there?

That would seem to follow, as with Europa and perhaps Enceladus. However, the energy source for any possible lifeforms in Ganymede's ocean would have to be volcanism; and there will probably be less of that on Ganymede than on Europa because Ganymede is further out and thus will have less tidal flexing.

It's also probable that the ocean on Ganymede will be a lot further down, for the same reason. It might be impossible, for the foreseeable future, to find out.

 

[Stephen Palmer]

Very interesting turn of events. Can't wait for 2030! I will be 68, if I get that far...

 

[Stephen Palmer]

Saturn news too.

 

[Mirannan]

Saturn news too.

Well, it was pretty obvious there was at least some liquid water under the crust of Enceladus - the cryovolcanism was evidence of that. Incidentally, there is also some, rather weaker, evidence of cryovolcanism on Titan - which raises the intriguing possibility of two entirely separate ecosystems, with completely different biologies and chemistries (water based and liquid methane based) on the same moon.

 

[BAYLOR]

That would seem to follow, as with Europa and perhaps Enceladus. However, the energy source for any possible lifeforms in Ganymede's ocean would have to be volcanism; and there will probably be less of that on Ganymede than on Europa because Ganymede is further out and thus will have less tidal flexing.

It's also probable that the ocean on Ganymede will be a lot further down, for the same reason. It might be impossible, for the foreseeable future, to find out.

Perhaps both an orbital probe above and unmanned probe on the surface could give us an idea of how far down the water is ?

 

[Mirannan]

Perhaps both an orbital probe above and unmanned probe on the surface could give us an idea of how far down the water is ?

Sorry, I should have been more specific. I meant finding out about life on (or in) Ganymede. One way of finding out about the depth of the ice might be seismometry?