Forecast for Titan: Wild weather could be ahead

May 22, 2013
Ligeia Mare, shown in here in data obtained by NASA's Cassini spacecraft, is the second largest known body of liquid on Saturn's moon Titan. It is filled with liquid hydrocarbons, such as ethane and methane, and is one of the many seas and lakes that bejewel Titan's north polar region. Cassini has yet to observe waves on Ligeia Mare and will look again during its next encounter on May 23, 2013. Credit: NASA/JPL-Caltech/ASI/Cornell

(Phys.org) —Saturn's moon Titan might be in for some wild weather as it heads into its spring and summer, if two new models are correct. Scientists think that as the seasons change in Titan's northern hemisphere, waves could ripple across the moon's hydrocarbon seas, and hurricanes could begin to swirl over these areas, too. The model predicting waves tries to explain data from the moon obtained so far by NASA's Cassini spacecraft. Both models help mission team members plan when and where to look for unusual atmospheric disturbances as Titan summer approaches.

"If you think being a on Earth is difficult, it can be even more challenging at Titan," said Scott Edgington, Cassini's deputy project scientist at 's Jet Propulsion Laboratory, Pasadena, Calif. "We know there are weather processes similar to Earth's at work on this strange world, but differences arise due to the presence of unfamiliar liquids like methane. We can't wait for Cassini to tell us whether our forecasts are right as it continues its tour through Titan spring into the start of northern summer."

Titan's north , which is bejeweled with sprawling hydrocarbon seas and lakes, was dark when Cassini first arrived at the in 2004. But sunlight has been creeping up Titan's since August 2009, when the sun's light crossed the equatorial plane at equinox. Titan's seasons take about seven Earth years to change. By 2017, the end of Cassini's mission, Titan will be approaching northern solstice, the height of summer.

Given the wind-sculpted dunes Cassini has seen on Titan, scientists were baffled about why they hadn't yet seen wind-driven waves on the lakes and seas. A team led by Alex Hayes, a member of Cassini's radar team who is based at Cornell University, Ithaca, N.Y., set out to look for how much wind would be required to generate waves. Their new model, just published in the journal Icarus, improves upon previous ones by simultaneously accounting for Titan's gravity; the viscosity and surface tension of the hydrocarbon liquid in the lakes; and the air-to-liquid density ratio.

This image shows the first flash of sunlight reflected off a hydrocarbon lake on Saturn's moon Titan. The glint off a mirror-like surface is known as a specular reflection. This kind of glint was detected by the visual and infrared mapping spectrometer (VIMS) on NASA's Cassini spacecraft on July 8, 2009. It confirmed the presence of liquid in the moon's northern hemisphere, where lakes are more numerous and larger than those in the southern hemisphere. Scientists using VIMS had confirmed the presence of liquid in Ontario Lacus, the largest lake in the southern hemisphere, in 2008. Credit: NASA/JPL/University of Arizona/DLR

"We now know that the wind speeds predicted during the times Cassini has observed Titan have been below the threshold necessary to generate waves," Hayes said. "What is exciting, however, is that the wind speeds predicted during northern spring and summer approach those necessary to generate wind waves in liquid ethane and/or methane. It may soon be possible to catch a wave in one of the solar system's most exotic locations."

The new model found that winds of 1 to 2 mph (2 to 3 kilometers per hour) are needed to generate waves on Titan lakes, a speed that has not yet been reached during Titan's currently calm period. But as Titan's northern hemisphere approaches spring and summer, other models predict the winds may increase to 2 mph (3 kilometers per hour) or faster. Depending on the composition of the lakes, winds of that speed could be enough to produce waves 0.5 foot (0.15 meter) high.

The other model about hurricanes, recently published in Icarus, predicts that the warming of the northern hemisphere could also bring hurricanes, also known as tropical cyclones. Tropical cyclones on Earth gain their energy from the build-up of heat from seawater evaporation and miniature versions have been seen over big lakes such as Lake Huron. The new modeling work, led by Tetsuya Tokano of the University of Cologne, Germany, shows that the same processes could be at work on Titan as well, except that it is methane rather than water that evaporates from the seas. The most likely season for these hurricanes would be Titan's northern summer solstice, when the sea surface gets warmer and the flow of the air near the surface becomes more turbulent. The humid air would swirl in a counterclockwise direction over the surface of one of the northern seas and increase the surface wind over the seas to possibly 45 mph (about 70 kilometers per hour).

"For these hurricanes to develop at Titan, there needs to be the right mix of hydrocarbons in these seas, and we still don't know their exact composition," Tokano said. "If we see hurricanes, that would be one good indicator that there is enough methane in these lakes to support this kind of activity. So far, scientists haven't yet been able to detect methane directly."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency. The mission is managed by JPL for NASA's Science Mission Directorate, Washington. JPL is a division of the California Institute of Technology in Pasadena, Calif.

Explore further: Cassini shapes first global topographic map of Titan

Related Stories

Titan's methane: Going, going, soon to be gone?

Apr 16, 2013

(Phys.org) —By tracking a part of the surface of Saturn's moon Titan over several years, NASA's Cassini mission has found a remarkable longevity to the hydrocarbon lakes on the moon's surface.

Cassini suggests icing on a Titan lake

Jan 08, 2013

(Phys.org)—It's not exactly icing on a cake, but it could be icing on a lake. A new paper by scientists on NASA's Cassini mission finds that blocks of hydrocarbon ice might decorate the surface of existing ...

Cassini spots mini Nile River on Saturn moon Titan

Dec 12, 2012

(Phys.org)—The international Cassini mission has spotted what appears to be a miniature extraterrestrial version of the Nile River: a river valley on Saturn's moon Titan that stretches more than 400 km ...

Cassini shapes first global topographic map of Titan

May 15, 2013

(Phys.org) —Scientists have created the first global topographic map of Saturn's moon Titan, giving researchers a valuable tool for learning more about one of the most Earth-like and interesting worlds ...

What's baking on Saturn's moon Titan?

Oct 16, 2012

(Phys.org)—Radar images from NASA's Cassini spacecraft reveal some new curiosities on the surface of Saturn's mysterious moon Titan, including a nearly circular feature that resembles a giant hot cross ...

Recommended for you

Another fireball explodes over Russia

1 hour ago

Why does Russia seem to get so many bright meteors? Well at 6.6 million square miles it's by far the largest country in the world plus, with dashboard-mounted cameras being so commonplace (partly to help ...

NASA's MMS observatories stacked for testing

2 hours ago

(Phys.org) —Engineers at NASA's Goddard Space Flight Center in Greenbelt, Md., accomplished another first. Using a large overhead crane, they mated two Magnetospheric Multiscale, or MMS, observatories – ...

ISEE-3 comes to visit Earth

3 hours ago

(Phys.org) —It launched in 1978. It was the first satellite to study the constant flow of solar wind streaming toward Earth from a stable orbit point between our planet and the sun known as the Lagrangian ...

Testing immune cells on the International Space Station

17 hours ago

The human body is fine-tuned to Earth's gravity. A team headed by Professor Oliver Ullrich from the University of Zurich's Institute of Anatomy is now conducting an experiment on the International Space Station ...

Easter morning delivery for space station

23 hours ago

Space station astronauts got a special Easter treat: a cargo ship full of supplies. The shipment arrived Sunday morning via the SpaceX company's Dragon cargo capsule.

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

orti
1 / 5 (10) May 22, 2013
OK. I'll take the cheap shot: Has man-made global warming reached even to there?
Sinister1811
1.5 / 5 (8) May 23, 2013
There's no doubt that if we were there, we'd be exploiting the large moon for its natural gas. I still wonder about the possibility of life on Titan, though.

More news stories

Another fireball explodes over Russia

Why does Russia seem to get so many bright meteors? Well at 6.6 million square miles it's by far the largest country in the world plus, with dashboard-mounted cameras being so commonplace (partly to help ...

ISEE-3 comes to visit Earth

(Phys.org) —It launched in 1978. It was the first satellite to study the constant flow of solar wind streaming toward Earth from a stable orbit point between our planet and the sun known as the Lagrangian ...

NASA's MMS observatories stacked for testing

(Phys.org) —Engineers at NASA's Goddard Space Flight Center in Greenbelt, Md., accomplished another first. Using a large overhead crane, they mated two Magnetospheric Multiscale, or MMS, observatories – ...

Easter morning delivery for space station

Space station astronauts got a special Easter treat: a cargo ship full of supplies. The shipment arrived Sunday morning via the SpaceX company's Dragon cargo capsule.