Featured Research

from universities, journals, and other organizations

Saturn's Moon Titan May Have Subsurface Ocean Of Hydrocarbons

Date:
April 6, 2009
Source:
Stanford University
Summary:
Saturn's largest moon, Titan, may have a subterranean ocean of hydrocarbons and some topsy-turvy topography in which the summits of its mountains lie lower than its average surface elevation, according to new research. Titan is also more squashed in its overall shape -- like a rubber ball pressed down by a foot -- than researchers had expected.

A radar image of some of the lakes of hydrocarbons spread across one of the poles of Titan, the largest of Saturn's moons. Colors have been altered to accentuate the topographic features.
Credit: Photo courtesy of NASA/JPL and the Cassini Project Office

Saturn's largest moon, Titan, may have a subterranean ocean of hydrocarbons and some topsy-turvy topography in which the summits of its mountains lie lower than its average surface elevation, according to new research.

Titan is also more squashed in its overall shape—like a rubber ball pressed down by a foot—than researchers had expected, said Howard Zebker, a Stanford geophysicist and electrical engineer involved in the work. The new findings may help explain the presence of large lakes of hydrocarbons at both of Titan's poles, which have been puzzling researchers since being discovered in 2007.

"Since the poles are squished in with respect to the equator, if there is a hydrocarbon 'water table' that is more or less spherical in shape, then the poles would be closer down to that water table and depressions at the poles would fill up with liquid," Zebker said. The shape of the water table would be controlled by the gravitational field of Titan, which is still not fully understood.

Hydrocarbons are the only materials on Titan's surface that would remain liquid at minus180 degrees Celsius, the average temperature of the moon's surface. Any water would be frozen, making it plausible that instead of groundwater, Titan would have the equivalent in hydrocarbons.

The research will be published in a paper in the journal Science.

Zebker, the lead author, and a group of colleagues have been making radar measurements of Titan's surface over the last four years using an instrument aboard the Cassini spacecraft, which is orbiting Saturn. Whenever Cassini passes close enough, they sweep beams of cloud-penetrating radar through Titan's thick atmosphere and across the surface. Using the radar data, they can calculate the surface elevations along the tracks of the sweep.

Combining more than 40 tracks across the surface, the researchers were able to calculate the three-dimensional shape of Titan.

Zebker said that there were theoretical reasons to expect that Titan was not a perfect sphere, but instead probably slightly oblate, or flattened, due to the centrifugal force from its rotation while orbiting Saturn. But the degree to which Titan is flattened exceeds what would be expected, based upon how close it is to Saturn and its roughly 16-day orbit.

It also turns out that Titan is not flattened uniformly. By way of analogy, if you were to put your foot on a rubber ball and press down, the ball would bulge out equally on all sides in the directions perpendicular to the downward force from your foot.

But the bulge of Titan is asymmetrical. The longest axis is oriented so that it points toward Saturn, a result of tidal forces from the planet. The shortest axis runs through the poles. And the other axis, oriented in the direction in which Titan orbits Saturn, is intermediate in length.

"While some asymmetry is expected from Saturn's gravitational pull, there is obviously something going on that causes Titan to have a different shape than expected," Zebker said.

There are several possible explanations for Titan's deformity. It might be that when the shape of the moon was determined, it was in an orbit closer to Saturn. "Another is that there are active geophysical processes occurring inside Titan that further distort the shape," Zebker said. "There are probably many other explanations as well, but we don't have enough information from this one experiment to be able to distinguish those."

Active geophysical processes might help account for another of Titan's oddities.

Zebker said that if you look at images of the surface of Titan, you see surface features that look every bit like mountains on Earth but don't have the high elevations compared to the plains stretching out around them.

"One of the really surprising finds that we have from this, is that the largest apparent continent is lower than the average elevation on Titan, as opposed to higher than the average elevation, as we have on the Earth," Zebker said.

"My favorite explanation is that the material that forms the mountains is simply more dense than the material surrounding them," he said. That would result in the mountains pushing down the surrounding crust, effectively putting the mountains in a basin of their own creation.

On Earth, the situation is the reverse: The crust that lies under the oceans is denser than the material that makes up the continental crust, where mountain ranges are built up.

"The things that we would expect to exist on the surface of Titan would either be solid hydrocarbon materials, essentially frozen ethane and methane, and that is fairly light, and then frozen water ice, which is denser," Zebker said. "If the mountains are composed of water ice and the plain features in between are composed of these solid hydrocarbons, that could lead to this kind of a situation."

Zebker said that research currently being conducted by other scientists to decipher the gravity field of Titan should help resolve some of the questions raised by his team's latest work. But he's holding off making any predictions.

"All of it surprises me because you never know what you are going to see," he said.


Story Source:

The above story is based on materials provided by Stanford University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Howard A. Zebker, Bryan Stiles, Scott Hensley, Ralph Lorenz, Randolph L. Kirk, and Jonathan Lunine. Size and Shape of Saturn's Moon Titan. Science, 2009; DOI: 10.1126/science.1168905

Cite This Page:

Stanford University. "Saturn's Moon Titan May Have Subsurface Ocean Of Hydrocarbons." ScienceDaily. ScienceDaily, 6 April 2009. <www.sciencedaily.com/releases/2009/04/090406091234.htm>.
Stanford University. (2009, April 6). Saturn's Moon Titan May Have Subsurface Ocean Of Hydrocarbons. ScienceDaily. Retrieved August 23, 2014 from www.sciencedaily.com/releases/2009/04/090406091234.htm
Stanford University. "Saturn's Moon Titan May Have Subsurface Ocean Of Hydrocarbons." ScienceDaily. www.sciencedaily.com/releases/2009/04/090406091234.htm (accessed August 23, 2014).

Share This




More Space & Time News

Saturday, August 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Did Russia Really Find Plankton On The ISS? NASA Not So Sure

Did Russia Really Find Plankton On The ISS? NASA Not So Sure

Newsy (Aug. 21, 2014) Russian cosmonauts say they've found evidence of sea plankton on the International Space Station's windows. NASA is a little more skeptical. Video provided by Newsy
Powered by NewsLook.com
Space to Ground: Hello Georges

Space to Ground: Hello Georges

NASA (Aug. 18, 2014) Europe's ATV-5 delivers new science and the crew tests smart SPHERES. Questions or comments? Use #spacetoground to talk to us. Video provided by NASA
Powered by NewsLook.com
Tiny Satellites, Like The One Tossed From ISS, On The Rise

Tiny Satellites, Like The One Tossed From ISS, On The Rise

Newsy (Aug. 18, 2014) The Chasqui I, hand-delivered into orbit by a Russian cosmonaut, is one of hundreds of small satellites set to go up in the next few years. Video provided by Newsy
Powered by NewsLook.com
This Week @ NASA, August 15, 2014

This Week @ NASA, August 15, 2014

NASA (Aug. 15, 2014) Carbon Observatory’s First Data, ATV-5 Delivers Cargo, Cygnus Departs Station and more... Video provided by NASA
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins