Pluto May Have a Subterranean Liquid Ocean Featuring Ice II

Pluto may no longer technically be a planet, but the dwarf planet continues to yield interesting insights and discoveries- most interestingly the possibility of a subsurface liquid ocean still swirling around within it.

After an arduous 10-year voyage, the New Horizons probe reached Pluto last year and documented its aberrant topography and cloudy atmosphere.

Brown University researchers Noah Hammond, Amy Barr and Marc Parmentier of the Planetary Science Institute have analyzed the data returned by New Horizons using a thermal evolution model. They believe that the formation of long, deep rifts that have expanded along Pluto’s surface are consistent with the activity of a large subsurface ocean expanding as it freezes. The tectonic activity evidenced on the planet’s surface suggests the presence of an ocean that is frozen or in the process of freezing.

They now believe that, taking into account information about Pluto’s density and size, the water freezing within Pluto has formed a rare type of compacted ice crystal known as ice II. Ice II, unlike normal ice which features hexagonal crystals, has a rhombohedral structure due to the extreme pressure under which it is formed.

Given the compacted nature of ice II, if the oceans under Pluto’s surface had completely frozen into ice II millions of years ago, the dwarf planet would have actually shrunk further, giving further justification for its diminutive classification. Interestingly, however, Pluto has not shrunk to the dimensions that the scientists’ model has predicted, suggesting that the ocean is not yet completely frozen.

Hammond, the lead author of the study, exclaimed that it was absolutely fascinating that a liquid ocean could exist in a planet so far from the Sun.