Titan’s Flyby

Titan’s Flyby

Preview of a New World View?

Huygens’ probe will enter Titan’s thick atmosphere around the first of next year.
Credit: NASA/ESA

Is next week’s planned flyby of Saturn’s mysterious moon, Titan, going to discover a liquid or solid surface?

That is one question that the 1200 kilometer approach will seek to answer. Using radar and images, the mission team hopes this preparatory flight will unveil enough of Titan to plan their Christmas descent to the surface.

The tiny probe called Huygens will detach from its mother ship, Cassini, and take a few weeks to try its descent through Titan’s thick atmosphere.

It will be the first spacecraft to attempt to land on a moon in our solar system since the Soviet Union’s Luna 24 touched down on Earth’s moon nearly three decades ago, in 1976.

Even if next week’s flyby reveals new details about the liquid seas that would startle the planetary science community, actual descent will still probably be about flying blind. If the probe survives, it will have weathered a blanket of hydrocarbon haze and methane clouds to reach a surface that could consist of seven-kilometer-high ice mountains and liquid methane seas.

While on-board infrared imaging cameras can pierce the cloud cover, they can only reveal bright and dark spots on the surface, which are difficult to interpret. What Huygens will encounter at Titan’s surface will remain a mystery until the probe plops into an ocean or parachutes to solid ground. The bright areas could be a mixture of rock and water ice, much like the other icy moons that orbit Saturn. But the dark areas are candidates for tar or hydrocarbon-rich lakes, much like one might imagine a sea of oil reflecting little light back towards the atmosphere.

Titan descent by Huygens probe leaving Cassini storage, Christmas 2004. Image Credit: JPL/Space Science Institute

One bright region called Xanadu is a particularly intriguing region which may be a bizarre ice mountain around 23,000 feet high and drenched in hydrocarbon rain and smog.

The tentative plan for Huygens is to target the best of the bright and dark regions–the actual site will be selected after next week’s flyby but is considered a good bet to aim towards the equator, near the boundary of a dark area next to a bright one. If scientists get their wish, the probe may land in a pool of butane, propane and methane.

That kind of targetting would set off a wave of celebration for mission scientists. From a mere 45 minutes of data downlinked while the probe was still able to float on any liquid surface, the science team would look to overturn the hypothesis that only Earth has the right constitution for maintaining liquid pools anywhere in our solar system.

The atmospheres of both Titan and the early Earth were dominated by nearly the same amount of nitrogen, and the chemistry discovered on Titan could provide clues to the origins of life on our planet. Recent calculations have suggested that methane concentrations may be as high as ten percent–a figure that would top the most hazardous smog encountered on Earth.

Related Web Pages

Saturn Edition, Astrobiology Magaz.
Saturn’s Rings in UV
Cassini Closes In on Saturn

Saturn– JPL Cassini Main Page
Lord of the Rings
Space Science Institute, Imaging Team Boulder, Colorado
Saturn: The Closest Pass