Cracks in Pluto’s Heart reveal presence of liquid water ocean beneath ice shell

Cracks in Pluto’s Heart reveal presence of liquid water ocean beneath ice shell

Researchers have used mathematical models and images captured by the New Horizons spacecraft to probe the global subsurface ocean that is likely to exist beneath Pluto. The distant dwarf planet has managed to retain sufficient heat for liquid water to exist beneath its surface. If humans somehow reached the subsurface ocean, they would effortlessly float in it.

Pluto, as captured by the New Horizons spacecraft. (Image Credit: NASA).

New Delhi: Researchers from Washington University have used mathematical models and images captured by the New Horizons spacecraft in 2015, to examine the subsurface ocean that is likely to exist on Pluto. The researchers estimate that the shell of frozen nitrogen, methane and water is between 40 and 80 kilometres thick.

This thick shell helps retain the heat necessary to maintain the subsurface liquid water ocean. For decades, scientists did not believe that Pluto supported a global subsurface ocean, as the planet is so distant from the Sun. The surface temperatures are about -220ºC, which is why the nitrogen and methane exist in solid form.

Pluto is also a small object, and basic calculations would indicate that it would be frozen all the way to the core, losing most of its heat shortly after it was formed. In recent years though, there are multiple lines of evidence hinting at a global subsurface ocean, including cryovolcanoes that spew ice and water vapour, as well as a lack of an equatorial bulge that only occurs if the world contains ice.

Floating in Pluto’s ocean

Billions of years ago, in the infancy of the Solar System, an impactor struck the dwarf planet, creating cracks and bulges in the ice in a region known as the Sputnik Platina Basin, which is also considered Pluto’s heart. Using mathematical models to explain the observed features, allowed the researchers to determine the existence of the global subsurface ocean, as well as its density.

The study indicates that Pluto’s ocean is about eight per cent denser than the seawater on Earth. The density explains the abundance of fractures seen on the surface. A less denser ocean would cause the ice shells to collapse, with many more fractures visible. A denser ocean would cause fewer fractures.

Pluto is a planet, at least for some scientists

A paper describing the findings has been published in Icarus. Lead author of the study, Alex Nguyen, says, “From my perspective, it’s a planet.” There is a raging scientific debate on whether Pluto should be considered a planet. The International Astronomical Union demoted Pluto in 2006, but Planetary Scientists, who actually study such worlds, want to reclassify it as a planet.

There are no plans to return to Pluto any time soon, so scientists will have to use the data from the New Horizons probe for at least a couple of decades into the future.