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Colloquium Speaker: Moons with Hidden Oceans Could Harbor Life
November 13, 2014

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Read up on Kevin P. Hand’s travels and you might imagine him as a scientist-adventurer with exploits worthy of a Hollywood action movie.

He’s explored the Dry Valleys of Antarctica, the glaciers of Kilimanjaro and the eerie, ocean depths of the Mariana Trench.

But the journey that occupies his mind most often is one that, for now, is an unrealized dream: A deep dive into the strange, hidden oceans thought to be sloshing within moons of Jupiter and Saturn.

It’s possible that unimagined forms of life are swimming there.

“I hope that some 400 years from now our descendants will be able to look back at our time, these next few decades, and they will be able to say, ‘It was then, that time period when the scientists and engineers … built the spacecraft, built the instruments, flew the missions and did the experiments that discovered life beyond Earth and brought our universe to life,” he said.

Hand, the Jet Propulsion Laboratory’s deputy chief scientist for Solar System Exploration, visited NASA’s Langley Research Center in Hampton, Virginia, Nov. 4 to give a Colloquium series talk titled “Ocean Worlds of the Outer Solar System.”

In an enthusiastic presentation featuring everything from complex physics equations to video of a prototype robot crawling along the underside of an Alaskan ice sheet, he described worlds radically different from Earth, but similar to our home planet in one key respect.

Jupiter’s moon Europa and Saturn’s moon Enceladus both are thought to hold lots of liquid water. It’s believed to be undulating just beneath their icy surfaces.

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“Just about everywhere we’ve gone on Earth and found liquid water, we have found life,” Hand said. “So, water has long been at the center of NASA’s search for life beyond Earth. It’s part of our mantra: Follow the water.”

Europa and Enceladus are two of the best places in the solar system to do that, Hand said. “They could harbor a second, independent origin of life,” Hand said. “Their biochemistries could be quite different from what we know of life here on Earth.”

At one time, conventional wisdom said that only worlds blessed with thick atmospheres, an abundance of liquid water and Earth-like temperatures could give rise to life. Hand describes that as the Goldilocks scenario, meaning that some worlds were considered too cold, others were too hot and only those in a solar orbit similar to the Earth’s were just right.

“But what’s happening is there’s a new Goldilocks in town,” Hand said in an interview before his talk. “There’s a new Goldilocks scenario for habitability, where the availability of liquid water is maintained by a combination of radiogenic decay of heavy elements like uranium, thorium, potassium, things that are in the rocks, and perhaps more importantly, the tidal energy tug and pull as these moons move around their gas giant parent planets.”

Why do scientists believe that these particular moons are hiding vast oceans of liquid water? In the case of Enceladus, a NASA probe has already sniffed it out. The Cassini spacecraft is orbiting Saturn and has taken photos and made measurements of its composition based on reflected light and the moon’s gravitational pull. The spacecraft has also photographed jets or plumes that spray up from fractures on the icy surface.

“The Cassini spacecraft has actually taken a taste of those plumes with a mass spectrometer and figured out that the material is water, but it’s also got some carbon dioxide, some methane and some organic compounds in it. And, there’s even some salts in that plume material,” Hand said. “The salts and the organics and the other materials that are in those jets, really serve as a smoking gun for this subsurface sea.”

Ultimately, scientists are eager to shift from studying the worlds’ chemical and geological composition to answering the bigger question.

“Of course, what we want to do with a future mission, is actually detect life,” Hand said. He showed an animated video depicting how an imagined spacecraft could someday land on Europa’s surface and deploy a melt probe using heat to drill down through the thick layers of ice to reach the ocean below. There, an autonomous underwater vehicle could swim to the ocean floor in search of hydrothermal vents and the creatures that might live there.

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“We’re a long ways off from there, but we are taking some baby steps toward that,” Hand said.

Landing on the surface of these worlds may not be the next step in exploration. Using remote sensing techniques, NASA may be able to search for life with an orbiting spacecraft.

Many established remote sensing technologies measure factors related to photosynthesis. Presumably, those won’t be useful at Europa, so scientists are working on techniques that will help them search for a different set of chemical signatures or life signs. A device called the Multi Channel Spectrometer for Europa or MUSE is being built to do just that.

As for Enceladus, NASA continues to study and interpret the wealth of data gathered by Cassini.

Cassini is now in what Hand calls its “extended-extended mission,” meaning its twilight years. It will continue to orbit Saturn and harvest data until 2017. After making several more flybys of the Enceladus and its sister moon, Titan, the probe will prepare for its final assignment.

“The Cassini spacecraft will have a spectacular finale,” Hand said. In its final orbits, it will dive between Saturn’s rings, taking pictures and readings all the way.

“Eventually, on the last orbit the Cassini spacecraft will plunge into Saturn’s atmosphere and go to a stormy death within Saturn. So, stay tuned for that. It’s going to be a wonderful few years.”

Sam McDonald
NASA Langley Research Center

Kevin P. Hand of NASA's Jet Propulsion Laboratory says plumes of water seen shooting from the surface of Enceladus, a moon of Saturn, indicate a sub-surface ocean.
Kevin P. Hand of NASA's Jet Propulsion Laboratory says plumes of water seen shooting from the surface of Enceladus, a moon of Saturn, indicate a sub-surface ocean.
Image Credit: 
NASA/David C. Bowman
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Kevin P. Hand, deputy chief scientists for solar system exploration for NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Kevin P. Hand is deputy chief scientists for solar system exploration for NASA's Jet Propulsion Laboratory in Pasadena, Calif. He researches the origin, evolution, and distribution of life in the solar system with emphasis on moons of the outer solar system that likely have liquid water oceans.
Image Credit: 
NASA/David C. Bowman
Image Token: 
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This is an artist's conception depicting the surface of Jupiter's moon Europa.
This image is an artist's conception depicting the surface of Jupiter's moon Europa.
Image Credit: 
NASA
Image Token: 
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Page Last Updated: November 13th, 2014
Page Editor: Samuel McDonald