Pluto May Have A Secret Super Salty Liquid Ocean

Pluto may have a liquid ocean hidden beneath its surface, according to researchers, the evidence of which has been growing. NASA's New Horizons spacecraft has contributed toward that pool of evidence, and now researchers with Brown University have built upon it, developing models of the planet in order to estimate how thick this buried ocean may be. Based on their work, a newly published study estimates that Pluto could have an undersurface layer of salty liquid water that is more than 100 kilometers thick.

The models looked into impact dynamics to help estimate how much liquid may be beneath the surface. The study cites both surface-level 'tectonic evidence' as well as interior thermal models as factors in the estimates, both of which indicate that a liquid water ocean — with a very high salt level akin to the Dead Sea — may be buried within.

The work was led by Brandon Johnson, a geologist with Brown University. According to Johnson, "...it's not easy to infer [the ocean's] size or anything else about it. We've been able to put some constraints on its thickness and get some clues about composition."

The hints about Pluto's underground ocean revolve around the planet's 'heart' — that is, the Sputnik Planum, specifically the western side of it. This region is essentially a giant impact crater, and, based on observations, it sits at the tidal axis that links the planet with its biggest moon, Charon. Because of the way the two planets are locked together, researchers have estimated the Sputnik Planum region is a positive mass anomaly, something with a higher level of mass than elsewhere on the planet.

Given that an impact basin results from a large object slamming into the ground, ejecting material away, the researchers would expect a negative — rather than positive — mass anomaly. Nitrogen ice building up in the impact basin is part of the reason, but researchers say the ice isn't present in great enough quantities to be the sole explanation.

That spurred the notion that liquid may exist beneath the surface, an idea due to a geological phenomenon called isostatic compensation, which would result in basically a welling of water beneath the impact zone, returning that area to a neutral mass. The ice, then, would form on the top, causing the mass to tip the scales, resulting in the positive mass researchers have observed.

Both ocean thickness and salt content have a large effect on the resulting positive mass, though, based on the researchers' models. Using simulations, they estimated that the ocean is at least 100 kilometers thick and has a salt content of at least 30-percent salinity.

SOURCE: Brown University