New Horizons Finds Evidence Of Subsurface Ocean On Pluto

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New Horizons has allowed for simulations of Pluto’s geological evolution, and these simulations have suggested more evidence that a liquid ocean may lie beneath the planet’s young surface.

For a long time now there has been speculation that an ocean lies beneath Pluto’s frozen surface, but, until now, this observational evidence has been inconclusive. However, with the recent New Horizons mission, increased observation has created some clues as to what lies beneath.

Pluto’s secret

The most important discovery by NASA’s New Horizons mission, which flew by Pluto on July 14, 2015, is that the planet has an active geology. This came as a surprise to most scientists, as Pluto orbits the sun around 40 times further away than the Earth does. Since it it so far away, shouldn’t the dwarf planet be a barren, frozen wasteland? Thanks to new evidence, this is not the case.

In fact, Pluto has a very complex geology, composed of a very young surface composed of a rich assortment of chemicals, including water, ammonia, and methane ices. The planet’s youth was caused by a complex relationship between the surface ice sublimating into Pluto’s thin atmosphere. Internal motions of ice act somewhat like a lava lamp, slowly shifting chemicals from below.

This behavior, a dynamic one, seems somewhat odd and is in itself a strong pointer that Pluto has an ocean, though not an ocean like on Earth. In a new paper published by the journal Geophysical Research Letters, scientists have carried out a number of numerical simulations of Pluto’s geological evolution, and the conclusions are nothing short of fascinating.

“Thanks to the incredible data returned by New Horizons, we were able to observe tectonic features on Pluto’s surface, update out thermal evolution model with new data and infer that Pluto most likely has a subsurface ocean today,” said head author and graduate student Noah Hammond, of Brown University. “What New Horizons showed was that there are extensional tectonic features, which indicate that Pluto underwent a period of global expansion. A subsurface ocean that was slowly freezing over would cause this kind of expansion.”

Evidence shows subsurface ocean probable

As everyone knows, as water freezes, it expands. Pluto shows geological features that suggest it underwent expansion. However, how can one know that the dwarf planet’s subsurface ocean has not already frozen ages ago? If this was the case, then the freezing process would have caused the entire planet to shrink.

Pictures taken by New Horizons show no evidence of Pluto contracting. In fact, evidence shows signs that Pluto has been expanding.

“Our model shows that recent geological activity on Pluto can be driven just from phase changes in the ice – no tides or exotic materials or unusual processes are required,” said senior scientist and co-author of the study Amy Barr.

“If Pluto’s most recent tectonic episode is extensional, that means that Pluto may have an ocean at present. This lends support to the idea that oceans may be common among large Kuiper Belt objects, just as they are common among the satellites of the outer planets.”

This new model certainly bolsters the theory for an ocean environment in the furthest reaches of the solar system. “That’s amazing to me,” said Hammond. “The possibility that you could have cast liquid water ocean habitats so far from the sun on Pluto – and that the same could also be possible on other Kuiper Belt objects as well – is absolutely incredible.”

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