Life on Saturn moon? Discovery of hidden ocean on Titan tantalizes.

Scientists already knew Titan has the building blocks for organic life in abundance. Now, the discovery of a underground sea with liquid water adds another intriguing element. 

|
NASA/AP/File
This image from NASA's Cassini spacecraft shows Saturn's largest moon, Titan, passing in front of the planet and its rings. A new study released Thursday suggests there may be an ocean below Titan's frigid surface.

A global ocean appears to lurk miles beneath the surface of Saturn's moon Titan, adding to the allure of an object rich with the building blocks of organic life and often likened to Earth before life emerged.

Cassini has already found large lakes – most likely made of hydrocarbons such as liquid methane – on Titan's surface. But a team of scientists using NASA's Cassini spacecraft have now found indirect but telltale signs of a subsurface sea, perhaps of water as well as ammonia, which would act like antifreeze. 

The data suggest that the ocean, perhaps more than 15 miles deep, is sandwiched between two layers of ice, each less than 60 miles (100 kilometers) thick. It rides atop one layer of ice covering the moon's rocky core and appears to be capped with another ice layer that forms Titan's surface. 

Titan has captured the imagination of scientists hunting for potential habitats for simple forms of life for decades. The temperature at Titan's surface is unbearably cold, minus 290 degrees Fahrenheit. It is paved with the methane ices and other organic solids on which Cassini's Huygens probe landed on Jan. 14, 2005. Its atmosphere is thought to mirror the composition of Earth's atmosphere before the emergence of life some 3.8 billion years ago. 

As hostile as the surface seems to be, "liquids from below would enhance the possibility of life being on the surface" as well as enhancing the possibility of aquatic habitats deep beneath Titan's crust, says Dirk Schulze-Makuch, an astrobiologist at Washington State University in Pullman with a keen interest in Titan's potential habitability.

Thursday's report represents "a nice step forward" in establishing an ocean's presence on Titan, he says. 

The new finding adds Titan to the growing list of moons thought to have subsurface oceans. The icy surface of Jupiter's Europa is believed to hide a vast ocean, and data from Cassini suggest a large, if not global, region of water or slush under the icy sheath of Saturn's Enceladus. Neptune's moon Triton may also have a subsurface ocean, and Ganymede and Callisto, two more Jovian moons, also are though to have under-ice seas.

But Titan stands out because researchers know that organic compounds are abundant there. 

Researchers led by Luciano Iess, a scientist at the Universita La Sepienza in Rome, used radio signals from Cassini to track changes in the effect Titan's gravity has on the orbiter during flybys. These readings allow the team to measure the strength of Titan's gravity in the regions Cassini overflies.

This process allows researchers to "weigh the moon, basically," says Sami Asmar, a scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and a member of the team that reported its results on Sciencexpress, the web outlet of the journal Science.

If Titan was solid, its gravity field wouldn't change. Even when the moon comes closest to Saturn on its elliptical orbit – experiencing Saturn's strongest tug – its mass would remain fairly evenly distributed throughout the object. 

But Titan's gravity changes as it progresses along its orbit, the team found. The side of the moon that always faces Saturn bulged as Titan made its closest approach to the ringed planet.

"We caught Titan in the act of deforming," Mr. Asmar says.

This tidal bulge represents a redistribution of material within the moon's interior – a telltale sign that there is likely a fluid layer in the moon's interior.

It is as though Titan's rocky core with its icy cover was being drawn through the global subsurface ocean toward Jupiter as the moon made its closest approach, creating the bulge.

The friction of the moon's tidal interaction with Saturn generates heat, which could help sustain the ocean's liquid state – as is the case within Enceladus and Europa.

The observation of a global ocean beneath Titan's icy exterior is indirect, Asmar says, "But it's real evidence."

[Editor's note: This article has been updated to correct Sami Asmar's title.

You've read  of  free articles. Subscribe to continue.
Real news can be honest, hopeful, credible, constructive.
What is the Monitor difference? Tackling the tough headlines – with humanity. Listening to sources – with respect. Seeing the story that others are missing by reporting what so often gets overlooked: the values that connect us. That’s Monitor reporting – news that changes how you see the world.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.

QR Code to Life on Saturn moon? Discovery of hidden ocean on Titan tantalizes.
Read this article in
https://www.csmonitor.com/Science/2012/0628/Life-on-Saturn-moon-Discovery-of-hidden-ocean-on-Titan-tantalizes
QR Code to Subscription page
Start your subscription today
https://www.csmonitor.com/subscribe