Being a hell of a long way from the sun and having a mean surface temperature of -380 degrees Fahrenheit, watery seas on Pluto might seem like a lofty claim, but the notion that a liquid ocean once existed under Pluto’s icy crust is an older idea than you might think. In 2011 (three years after its famous demotion to dwarf-hood), scientists suspected that Pluto could hold a liquid ocean under two conditions – if its core was potassium rich enough that water could be heated by radioactive decay AND the ice on the surface moves slowly enough that not too much of that heat would escape. More recently, a third factor has been constructed that suggests not only that there was an ocean, but that there could still be one. Geoffrey Collins (Brown University) and Amy Barr (Wheaton College) have proposed a theory in the journal Icarus that the possible accumulation of agents like ammonia and salts in the water on Pluto may have prevented all of it from freezing.
Pluto and its moons as seen from the Hubble Space Telescope. (NASA)
Billions of years back, a giant object smashed into Pluto and knocked a piece off of it that eventually formed into Pluto’s moon Charon. The heat released from this event may have melted the interior of Pluto and created an ocean. Most feel that this ocean didn’t last for long, but Collins and Barr argue that it could still be there. As water closer to the surface of these ancient oceans froze into a thicker and thicker ice sheet, ammonia and low-eutectic salts could have become so concentrated in the remaining liquid water that the mixture could have eventually taken on a composition similar to anti-freeze.
Some of these questions could be answered in July of next year when the New Horizons spacecraft makes a fly-by of Pluto and sends pictures back to Earth. Many scientists are hoping we’ll see cracks along the surface of the dwarf planet. These cracks would indicate there was once a liquid ocean underneath the crust – and even that there may still be one. It’s not a guarantee that we’ll get a clear glimpse of Pluto’s possible fault lines on the flyby, however, since the body’s elliptical orbit could have eroded the surface too greatly. When Pluto is farthest from the sun, its atmosphere freezes to its surface and then thaws out when it comes in closer. Years of this dramatic shift between freezing and thawing could mean signs of tectonic activity may have long since worn off.
Claims of watery worlds under the crusts of Enceladus and Europa have already been all but confirmed, but what other bodies do you think are hiding water under their icy surfaces? Call it first in the comment section below.