Pluto may have been downgraded to “dwarf planet,” but its potential significance is greater than ever. While Pluto may not seem close enough to the sun to contain water, researchers now think that it harbors a below-ground ocean.
Sputnik Planitia. Credit: NASA/JHUAPL/SwRI
The most distinct feature of Pluto’s surface is a large depression called Sputnik Planitia (often referred to as the “heart” of Pluto), which researchers believe has a direct impact on the planet’s rotation due to gravitational mechanics. Like Earth and the moon, Pluto has a gravitational relationship with its moon, Charon. Sputnik Planitia’s location on the planet happens to be about as far away from Charon as possible, which leads researchers to draw a few different conclusions. Sputnik Planitia covers a crater thought to have begun with an impact. Since then, there’s clearly a longstanding relationship between the three bodies.
Sputnik Planum in detail. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
The most likely explanation for Sputnik Planitia’s position opposite Charon is that the density of the basin is greater than that of other areas of Pluto, which raises another question: what exactly is Sputnik Planitia made of? Or more accurately, what’s under the ice?
Recent photos from NASA’s New Horizons mission show a 600-mile-wide ocean topped by nitrogen ice, which churns in an ongoing process that continually replaces older ice with newer ice. A recent study published in Nature suggests that remarkably, this subsurface ocean isn’t frozen. It has a viscous consistency and contains large amounts of ammonia, which prevents it from solidifying. This theory is consistent with New Horizons’ chemical analyses of Charon, and as well as another of Pluto’s smaller moon, both of which contain ammonia.
Elevation Map of Sputnik Planum. Credit: NASA
While marine animals on Earth wouldn’t be able to survive there, it’s possible that other life forms could. The finding also means that Pluto’s diminutive neighbors could also have their own oceans, each with the possibility of life. Such life would likely be quite primitive, but the mere possibility is exciting enough to put these dwarf planets in the spotlight usually reserved for their bigger counterparts.