Artist's conception of clouds in Pluto's atmosphere. (Photo by: Photo 12/Universal Images Group via Getty Images)

869722242

Artist's conception of clouds in Pluto's atmosphere. (Photo by: Photo 12/Universal Images Group via Getty Images)

The Secret of Pluto’s Ocean

When we think of an ocean, we don't necessarily think of Pluto. If we can’t see the liquid water, why do astronomers think it’s there?

February 18, 2020

When we think of water on a planet, our minds go to certain images: waves lapping at a sandy beach, a thundering waterfall, and meandering brook. You know, the familiar liquid sites here on Earth, where water is abundant on the surface.

While our home planet is indeed the only known world to host liquid water on its surface, it’s not the only place in the solar system where you can slap on a swimsuit and take a dip.

And perhaps the most unlikely place to host an ocean of liquid water? Tiny little Pluto, a world not even as big as our Moon, clinging to the frozen fringes of our solar system like an unwanted runt of the litter.

Water? On Pluto? We have pictures of Pluto thanks to the historic New Horizons flyby in 2015. We saw many wondrous and mysterious things: nitrogen ice glaciers, water ice mountains, and a thin atmosphere. But we didn’t see any water. So where is it?

Pluto’s ocean, like the rest of the liquid water in the solar system, is hidden, a secret buried under miles of rock-hard ice. But if we can’t see it, why do astronomers think it’s there?

A scene on Pluto with Charon, its giant moon.

112716774

A scene on Pluto with Charon, its giant moon.

Photo by: Ron Miller

Ron Miller

For one, Pluto has a healthy fraction of radioactive elements inside of it. These elements decay over time, releasing heat. Similar elements inside the Earth generate enough heat to turn rock into magma. So out there on the edge of the solar system, it’s not a stretch to imagine the heat turning ice into water.

Second, the nitrogen glaciers. The surface of Pluto has a giant, gaping wound called the Sputnik Planitia, home to a network of slow-moving interlocking glaciers. Something is keeping those glaciers churning and the likely culprit is heat escaping the core – the same heat that might liquify water deeper down. And our best guess as to how it formed in the first place? Astronomers suspect something large smashed into Pluto long ago, causing water to gush out and seep over the surface – a lesion that never quite healed.

Lastly, there are curious features all over the face of Pluto, subtle cracks and fissures that are the telltale signs of tectonic activities. These are the same kinds of rifts and mountain chains you might find on the Earth. In the outer solar system, usually gravitational interactions are responsible for such shifts in a crust, but Pluto has nothing big enough nearby to cause that kind of stress.

But if it had a liquid water ocean that was slowly cooling – but not yet completely frozen – the expansion of that water as it turned to ice would pop and crack the crust, causing the features that we see.

It’s not a slam-dunk case. We’re not as confident about water inside Pluto as we are on, say, Europa or Enceladus. But it’s an intriguing set of clues that point to an ocean completely encircling the little world to a depth of over a hundred miles. In other words, more liquid water than the Earth has.

So on the next mission to Pluto, you better pack the scuba gear.

#TeamPluto premieres Tuesday, February 18th at 11pm ET/PT on Discovery and Discovery Go.

Paul M. Sutter

Paul M. Sutter is an astrophysicist at Stony Brook University and the Flatiron Institute, host of Ask a Spaceman and Space Radio, and author of How to Die in Space.

Next Up

The Perseid Meteor Shower Reaches its Peak

Stargazers rejoice! The annual Perseid meteor shower is upon us. Here's what you need to know...(updated August 11, 2022)

Scientists Have Discovered Enormous Balloon-Like Structures in the Center of Our Galaxy

There's something really, really big in the middle of our Milky Way galaxy — one of the largest structures ever observed in the region, in fact.

Astronomers May Have Found a Rare “Free-Floating” Black Hole

How do you see a perfectly black object in the middle of a pitch-dark night? It sounds like the start of an annoying riddle, but it’s really the question faced by astronomers when they want to search for black holes.

Saving Earth from Killer Asteroids

Only about 40% of an estimated 25,000 near-Earth asteroids with the potential to destroy the planet have been detected. Scientist Dr. Ed Lu, along with his nonprofit B612 are working to create a way to detect the other 60%.

How Do We Know How Old the Sun Is?

Scientists estimate that our Sun is about 4.57 billion years old. They’re surprisingly confident about that number, too, which opens up an immediate question: how do we know that? The short answer is “a lot of science and math”, but I have a feeling you’re not here for the short answer.

Scientists in China Discover Rare Moon Crystal that Could Power Earth

A rare lunar crystal found on the near side of the moon is giving scientists hope of providing limitless power for the world – forever.

How to Save Humanity from Extinction

Here are some goals we need to achieve if we want to reach our 500,000th birthday as a species.

The Densities Of The Planets

A planet's density tells us more information than its size.

The Butterfly Effect Is Why It's Impossible to Predict the Weather

This is a concept invented by the American meteorologist.

Rhnull, the Rarest Blood Type on Earth, Has Been Called the "Golden Blood"

The extremely rare blood type is shared by only a handful of people on Earth.

Related To: