Titan Lifting Veil on Xanadu
The veils of Saturn’s most mysterious moon have begun to lift in Cassini’s eagerly awaited, first glimpse of the surface of Titan, a world where scientists believe organic matter rains from hazy skies and seas of liquid hydrocarbons dot a frigid surface.
|Scientists would like to know more about the origin of the ring ‘spokes’ imaged on Saturn by Voyager, but not so far by the current Cassini images. Image Credit: Cassini Imaging Team/Boulder/ ciclops.org|
Titan, a major target of interest for the Cassini orbiter, and the destination of its piggybacked, European-built Huygens probe, may hold clues to Earth’s hydrological cycle, its greenhouse effect, and even the origins of life.
Images returned in mid-April by NASA’s Saturn-bound Cassini spacecraft, showing features previously observed only in Earth-based telescopes, have imaging scientists excited and optimistic about the prospects for a successful upcoming exploration of the haze-enshrouded moon that has intrigued planet-watchers for decades. Titan, nearly the size of Mercury at 5,100 kilometers (3,200 miles) across, is the largest single expanse of unexplored terrain remaining in the solar system today.
The Titan-viewing geometry presently available to Cassini on its approach to Saturn is not optimal. Nonetheless, surface features on the moon several hundred kilometers (a couple of hundred miles) across are apparent. Over the next two months, features as small as 44 kilometers (28 miles) should become visible.
"This is our first moment of reckoning," said Dr. Carolyn Porco, leader of the imaging team and director of the Cassini Imaging Central Laboratory for Operations (CICLOPS) at the Space Science Institute in Boulder, Colo. "The mere fact that we can see the surface at all with just some rudimentary image processing, when the geometry for surface viewing is not the most favorable, says that in a very short time, we can rightfully expect to see sights on Titan that have never been seen before by anyone."
John Barbara, an imaging team associate and scientific analyst at NASA’s Goddard Institute for Space Studies in New York, is interested in detecting clouds in the lower Titan atmosphere and measuring their motions. Seeing near-surface clouds through the hazy Titan atmosphere carries the same challenges as seeing the surface. "At this stage in the game, to discern large-scale surface features is really quite exciting’, he said. ‘It’s a wonderful indication that, if there are large cloud systems near the Titan surface, we will likely see them."
|The large, continent-sized, red feature in the banner image extending from 60 degrees to 150 degrees West longitude is called Xanadu. It is unclear whether Xanadu is a mountain range, giant basin, smooth plain, or a combination of all three. It may be dotted with hydrocarbon lakes, but that is also unknown. All that is presently known is that in Earth-based images, it is the brightest region on Titan. . Image Credit: Cassini Imaging Team/Boulder/ ciclops.org|
The next test will come on July 2, when the spacecraft makes a 350,000 kilometer (217,500 mile) approach to Titan over its south pole, offering the possibility, but not the certainty, of seeing features as small as a few kilometers.
"Although we can see large-scale surface contrasts through even a thick haze, the small-scale features can only be seen if the haze is thin," said Dr. Robert West, Cassini imaging team member and an atmospheric scientist at JPL. "So we don’t yet know if or how well we will be able to see fine details on the surface. But we will know for sure on July 2, and if we are successful, a whole new world will be opened to us."
|Scientists would like to know the origin of the atmospheric patches imaged on Saturn’s moon, Titan, as imaged by Hubble. Image Credit: Hubble Space Telescope/UA Smith|
Titan may have familiar geological constructs like mountains, canyons, craters, rivers, lakes, cataracts, wind-blown waves, shorelines, snow fields and other terrestrial-like features. But because of the frozen temperatures and the very un-Earthlike materials on its icy surface and in its atmosphere, scientists are expecting the unexpected.
"The next few months will read like an episode from Star Trek," said Porco. "It will be exploration at its finest and is precisely why we came."
Cassini is scheduled to arrive in orbit around Saturn on June 30 PDT.
It is noteworthy that the surface is visible to Cassini from its present approach geometry, which is not the most favorable for surface viewing. The success of these early Cassini observations portends success for upcoming imaging sequences of Titan in which the resolution improves by a factor of five over the next two months. These results are also encouraging for future, in-orbit observations of Titan that will be acquired from lower, more favorable phase angles.
The first opportunity to view small-scale features (2 kilometers or 1.2 miles) on the surface comes during a 350,000 kilometer (217,500 mile) flyby over Titan’s south pole on July 2, 2004, only 30 hours after Cassini’s insertion into orbit around the ringed planet.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Office of Space Science, Washington. The imaging team is based at the Space Science Institute, Boulder, Colo. The Space Science Institute is a non-profit organization of scientists and educators engaged in research in the areas of astrophysics, planetary science and the earth sciences, and in integrating research with education and public outreach.