Underground ocean discovered on Saturn moon

Add Enceladus, a small moon orbiting the giant ringed planet Saturn, to the growing list of places beyond Earth that have oceans – and prospects for hosting life, a study released on Thursday shows.

Situated some 1.3-billion kIlometres away in the outer solar system, icy Enceladus seems an unlikely place for liquid water.

But gravity measurements taken by Nasa's Saturn-orbiting Cassini spacecraft indicate the moon contains an underground ocean in its southern hemisphere. The ocean is believed to be at least as big as Lake Superior, according to research published this week in the journal Science.

Computer models indicate the ocean is likely sandwiched between the moon's rocky core and its ice-covered surface, said planetary scientist David Stevenson, with the California Institute of Technology.

It likely formed and is sustained by tidal heat from gravitational tugging by Saturn and sister moons on Enceladus.


Cassini previously discovered water plumes jetting out from hot spots in Enceladus's south pole. Analysis showed the plumes contain salts and organic molecules.

An underground ocean "provides one possible story to explain why water is gushing out of these fractures", Stevenson said in a statement.

'Place to look for life'
The prospect of liquid water, particularly water that comes close enough to rock to leach out minerals, raises the likelihood that Enceladus has chemistry suitable for life, planetary scientist Jonathan Lunine with Cornell University told reporters on a conference call on Wednesday.

"The interior of Enceladus is a very attractive potential place to look for life," Lunine said.

Enceladus, which is only about 500km in diameter, joins Saturn's large moon Titan and Jupiter's Europaand Ganymede as places beyond Earth that are likely to contain oceans.

Only Enceladus and Europa, however, show evidence that their oceans are in contact with rock.

To get Enceladus's gravity maps, scientists had to tease out signals in Cassini's radio transmissions that changed by just a fraction of a millimetre per second.

The measurements were made as Cassini flew close by Enceladus three times from 2010 to 2012. The flybys showed Enceladus had a different gravitational grip on Cassini depending on whether the spacecraft passed over the moon's northern or southern hemisphere.

Taking into account what materials are available in the outer solar system – namely rock and ice – the scientists then set about running computer models to assess the most likely cause of Enceladus's asymmetrical gravity.

Their answer: a large ocean about 10 kilometres deep that is covered by 30km to 40km of ice.

Follow-on missions
Cassini, which has been studying the Saturn system for a decade, has three more passes by Enceladus before its mission ends in September 2017. No more gravity measurements are slated during those flybys, however.

Scientists are working on follow-on missions proposed for both Enceladus and Europa.

"I don't know which of the two is going to be more likely to have life. It might be both. It could be neither. I think what this discovery tells us is that we just need to be more aggressive in getting the next generation of spacecraft both to Europaand to the Saturn system once the Cassini mission is over," Lunine said. – Reuters

These are unprecedented times, and the role of media to tell and record the story of South Africa as it develops is more important than ever. But it comes at a cost. Advertisers are cancelling campaigns, and our live events have come to an abrupt halt. Our income has been slashed.

The Mail & Guardian is a proud news publisher with roots stretching back 35 years. We’ve survived thanks to the support of our readers, we will need you to help us get through this.

To help us ensure another 35 future years of fiercely independent journalism, please subscribe.

Advertising

ANC wants pension funds to finance infrastructure build

The party released its plan for the reconstruction of the country’s post-coronavirus economy on Friday. This would involve changes to Regulation 28 of the Pension Funds Act

The case against Floyd Shivambu

The flow of money from VBS Bank would seem to suggest that the EFF’s second-in-command was an ultimate beneficiary of proceeds of a crime

Cabinet reshuffle rumours: Unlikely to happen any time soon, but…

Persistent rumours of a cabinet reshuffle may be jumping the gun, but they do reflect the political realignment taking place within the ANC

Nigeria’s anti-corruption boss arrested for corruption

Ibrahim Magu’s arrest by the secret police was a surprise — but also not surprising
Advertising

press releases

Loading latest Press Releases…

The best local and international journalism

handpicked and in your inbox every weekday