Cold-hearted Pluto may harbor icy ocean

Researchers believe the slushy ocean is right below the “heart” of Pluto. NASA

The dwarf planet Pluto may hold a tantalizing secret in its “heart”: a slushy ocean of ice water.

NASA researchers, including a prominent MIT scientist, previously have said that a flyby of Pluto in July 2015 by the New Horizons spacecraft detected a heart-shaped spot on its surface, called the Sputnik Planitia. The possible ocean may lie beneath the left side of that spot, the New Horizons team said in an article Wednesday in the journal Nature.

The ocean is believed to be under the heart-shaped Sputnik Planitia. NASA

“So it begins with Pluto’s now-famous heart, the Sputnik Planitia,” Richard Binzel, the MIT scientist who has worked on the New Horizons project since its beginning, said by phone. “When we look at it carefully, it has an inner region that is almost perfectly circular, so we think it began as a giant impact crater, creating what we call a basin.”

The existence of a subsurface ocean may solve a longstanding puzzle: Why Pluto’s brightest region, Tombaugh Regio, aligns almost exactly from the dwarf planet’s moon, Charon. The subsurface ocean, the new data suggest, may have served as a “gravitational anomaly,” or weight, which would play a role in Pluto and Charon’s gravitational tug-of-war.

Binzel said when this basin was created, it allowed a flowing substance to poke through the mantle below the crust.

“Some kind of dense viscous material was able to push up and make a bulge in the bottom of that impact basin, and when we try to analyze all the different things that this viscous bulge could be, a slushy ocean of water is the best fit to our models,” he said.

Binzel said researchers have seen similar bodies of flowing substances on Earth. “In the Earth, the places where we see positive gravity anomalies are where the crust is thin and some of the molten mantle of the earth is able to push itself up,” he said. “So we understand these anomalies on Earth are from some viscous material that’s able to push its way up.”

He said this discovery proves that researchers still have a long way to go to understand Pluto.

“I think the big picture is that this is telling us that Pluto is much more complicated, much more fascinating than we ever imagined,” he said. “That’s the lesson of exploration, it’s why we explore because nature continuously surprises us.”