Pluto’s Hidden Ocean
When NASA’s New Horizons cruises by Pluto in 2015, the images it captures could help astronomers determine if an ocean is hiding under the frigid surface. New research has not only concluded such an ocean is likely, but also has highlighted features the spacecraft could identify that could help confirm an ocean’s existence.
Pluto’s outer surface is composed of a thin shell of nitrogen ice, covering a shell of water ice. Planetary scientists have wanted to find out whether or not an ocean could exist underneath this icy shell, and what visible signs such an ocean might produce on the surface.
As spherical bodies spin, their angular momentum tends to push material towards the equator, forming a bulge. If Pluto boasts a liquid layer, the ice would flow, reducing such a protrusion. But finding a “frozen-in” primordial bulge, left over from when Pluto spun more rapidly, would signify a lack of ocean.
As Pluto cooled over its lifetime, the temperature changes resulted in a change in volume, creating surface stresses. Icy water beneath the shell would result in tensional stresses as the ice was stretched, while a solid layer would have meant compressional stresses as the material was squeezed. Such fractures would likely span the globe, rather than being unique to specific areas.
This is ideal, since New Horizons will not map the entire surface of Pluto. Because of the complications involved in going into orbit, the craft will only fly past the icy dwarf planet. Only the hemisphere facing the spacecraft near the time of the flyby will be mapped at the highest resolution, revealing ridges and valleys with heights and depths of 80 meters and potential geysers similar to those found on Saturn’s moon Enceladus.