Surface temperatures on Pluto are around -230C, making the likelihood of a liquid ocean on the dwarf planet's surface more than a little unlikely. In fact, scientists have long assumed that Pluto's surface is covered mostly with ice. What goes on beneath that ice, however, is something of a mystery.
Now, scientists have calculated that Pluto could actually be hiding subsurface oceans beneath its icy exterior. Moreover, if these liquid oceans consist of the same nitrogen/water mixture as the dwarf planet's icy shell, they could very well be home to extraterrestrial life.
Scientists believe that the likelihood of Pluto harboring subsurface oceans largely depends on two factors. First, the planet core would have to be rich in potassium. The idea is that the radioactive decay of enough potassium over time would release sufficient heat to melt the frozen oceans encasing the planet's core.
Second, the flow of ice on the planet's surface would need to be sufficiently slow-moving. Too much tectonic activity at the planet's icy surface would simply release the heat being generated by the planet's core into space. By acting as an insulating barrier, slow-moving surface ice would allow for heat to become trapped between it and the planet's core, allowing for subsurface oceans to form.
In a paper recently published in the journal Icarus, UC Santa Cruz researchers Guillaume Robuchon and Francis Nimmo calculate that given the estimated potassium contents of Pluto's core (which are thought to far exceed the levels necessary for producing heat sufficient for ice-melt), ice sheet movement on the planet's surface need to be slower than the pace of the glacial movement we're familiar with here on Earth in order to sustain a subsurface ocean.
While there currently exists no way of measuring the movement of ice on Pluto's surface from Earth, the researchers say that future image analyses by NASA's New Horizons probe could shed light on the Planet's subsurface characteristics.
Astronomers have observed that Pluto's spin is in the process of slowing down. Because rotating spherical objects tend to bulge at their equators, the slowing of Pluto's spin will allow for it to return to a more spherical shape.
Just how much the dwarf planet's shape relaxes, however, depends on its composition; according to the authors, a planet without a subsurface ocean will have a more difficult time returning to a spherical shape, and will show evidence of "fossil rotational bulge." If Pluto harbors a subsurface ocean, however, the scientists predict that it will be able to relax into a more spherical form.