Enceladus’s oceans may be the right saltiness to sustain life

[Buster's Uncle]

Enceladus’s oceans may be the right saltiness to sustain life
Karmela Padavic-Callaghan - 2h ago
New Scientist



© Provided by New Scientist
Enceladus has oceans under its icy surface Science Photo Library/Alamy


The way ice covers the surface of Saturn’s moon Enceladus suggests that the oceans trapped beneath it may be only a little less salty than Earth’s oceans. The finding adds to the possibility of Enceladus's ability to sustain life.

The surface of Enceladus is encased in clean, bright ice. Wanying Kang at Massachusetts Institute of Technology and her colleagues wanted to determine what kind of an ocean must hide beneath it to maintain the thickness of this ice shell.

Samples taken by the Cassini spacecraft of geyser-like jets of water from Enceladus’s surface previously showed that there is some organic matter and some energy that could sustain potential life on the icy moon. Considering the waters under Enceladus’s ice was the logical next step for inferring its habitability, says Kang.

The team devised a theoretical model detailing how ocean salinity, ocean currents and ice geometry affect each other on a planet or a moon, then tweaked it to best reproduce the properties of Enceladus’s ice.

The researchers found that saltier subsurface oceans correspond to thicker ice on a planet’s poles than over its equator and vice versa for fresher water. On Enceladus, ice is thinner over its poles than its equator and its specific variation in thickness suggests that its salinity could be as high as 30 grams of salt in a kilogram of water compared to 35 grams in the Earth’s oceans.

The researchers also determined details of water circulation under the moon’s ice. These currents are related to temperature differences across the water so understanding them is also important for determining habitability, says Kang.

The team found that some heat emanates from the bottom of the Enceladus’s ocean, possibly indicating the existence of heat vents in the ocean floor. Kang says that some astrobiologists have previously suggested that, like on Earth, such hydrothermal vents could be where life is found in the future.

David Stevens at University of East Anglia, UK says that the behaviour of ice and water on other planets is directly related to their habitability. At the same time, salinity is only one factor, he says.

Kang and her team are currently working on applying the new model to Jupiter’s moon Europa which is thought to have a higher salinity than both Earth and Enceladus. Ultimately, they want to pin down the details of the oceans of all icy moons and planets observed by space missions as a step towards better determining how habitable they all are.

Journal reference: Science Advances, DOI: 10.1126/sciadv.abm4665


https://www.msn.com/en-us/news/technology/enceladus-s-oceans-may-be-the-right-saltiness-to-sustain-life/

[Geo]

I wonder if the team took into account the equatorial bulge of Enceladus because it orbits a massive gas giant.

[Buster's Uncle]

IS there one?

[Geo]

IS there one?

Good question, but gravity says: 'always'.

[Unorthodox]

Does salinity even matter? 

I mean looking into some of the extremophiles, it seems life figures that [poop] out fairly easily. 

[Buster's Uncle]

It does seem like we have salt in our bodies because that was roughly the salinity level of the oceans when our ancestors crawled out - not that I've ever heard that the salt actually does anything...

[Geo]

Well, rumour is that without it we eventually become sick and die...

[Buster's Uncle]

Yeah - but I'm not aware of anything to it than 'always been there'.

[Unorthodox]

My point is that since life has adapted to a VAST range of salinity here on earth, does the specific level of salinity really matter? 

Yes, there may not be any halophobic organism examples (not 100% sure on that), but given how ubiquitous salt is on earth, that's not exactly a surprise that none needed to evolve.  AFAIK we had already inferred that the oceans there were salty...I'm failing to see how a specific level of salinity really makes life more/less likely. 

[Geo]

I don't know. For all I care it connects with the level of energy required to maintain life. Something that would be less readily available on an evironment like the oceans of Enceladus.

[Buster's Uncle]

Eh, just - it seems likely they're assuming too much about life requirement, calculating salinity...