It is easy to feel unhappy for Pluto since it got demoted to non-planet rank back in 2006, but if anything, our favorite cosmic oddity has only gotten more exciting since it broke out on its own. Studies propose it’s got strange gravity waves, a beating heart, and the way it interacts with solar winds is not like anything researchers have seen in our Solar System. And now it looks like it’s like a flowing, underground ocean. If that makes you feel a little odd, yep, it’s super strange and weird. How can a planet that is nearly 6 billion kilometers (3.67 billion miles) away from the Sun not be freezing to the core?
That question has been irritating scientists since NASA’s New Horizons probe completed its flyby of Pluto last July and found signs of tectonic activity upsetting its frosty surface that could only really be described by an underground ocean. And now a new model approves what NASA researchers have assumed, by revealing how Pluto would generally dry out like an overripe peach if it did not have liquid water giving its frozen crust a bit of area to move.
As Maddie Stone describes over at Gizmodo, when New Horizons sent back the clearest pictures ever captured of Pluto’s surface, there was a weird lack of what researchers refer to as compressional tectonic features, which are likely to form if the internal layers of liquid had frozen into a thicker form called ice II.
The image that gave away Pluto's secret. Credit: NASA/New Horizons
One of the team members behind the model, Noah P. Hammond from Brown University, told the press, "The foundation of ice II would cause Pluto to experience size contraction and compressional tectonic features to form on the surface."
In short, Hammond’s models presented that if Pluto’s liquid ocean had frozen dense, it would have been crushed by the thick outer shell into a dense ice II shape. Ice II is weird in that it contracts as it freezes, rather than expanding like normal ice, so if Pluto had an ice II ocean underneath its icy crust, it would have affected the whole thing to contract from the inside, in ways that would have been observable on the surface.
Hammond says, "As the tectonic features on Pluto’s surface are all extensional and there are no obvious compressional features, it proposes that ice II has not formed and that so, Pluto’s sub-surface ocean has possibly survived the past."
So what’s keeping Pluto’s assumed underground ocean so wet? The scientists believe it’s likely to the dwarf planet’s simmering core, which creates a whole lot of heat from the decay of radioactive features inside the surface. While this means that Pluto appears to be more habitable, or maybe slightly less cold than we believed, there is still not much chance of life on the planet. But what’s important in this discovery is the fact that liquid oceans can exist on dwarf planets, moons, and even bigger planets, without the tidal forces researchers had assumed were essential for keeping things nice and flowing.
Conor Gearin describes for New Scientist:"The moons of gas giants, like Jupiter’s moon Ganymede, have sub-surface oceans because tidal forces from the planet keep them spilling around. In contrast, Pluto seems to have a liquid ocean despite not suffering a large planet’s tidal pull."
Francis Nimmo of the University of California at Santa Cruz says, "You don’t need tidal heating to have an ocean, which is the main lesson. It means that other big Kuiper Belt objects out there could have oceans, also."
Obviously, nothing’s confirmed until some robot drone jumps into the Pluto’s underground ocean, but the case is looking pretty strong for Pluto’s sloshy interior.