SPACE.com -- Titan Images Renew Excitement for Mysterious Moon

False-color map of the surface of Titan, made from images taken by the Hubble Space Telescope. Click to enlarge.

New images of Titan's surface, taken from the Canada-France-Hawaii Telescope. Click to enlarge.

New Images of Titan May Help Cassini Scientists

The Cassini Mission -- space.com's coverage


	Titan Images Renew Excitement for Mysterious Moon By Maia Weinstock Staff Writer posted: 07:21 pm ET 15 August 2000

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Astronomers working at the Canada-France-Hawaii Telescope in Hawaii have released several new images of Saturns moon Titan, re-igniting scientists excitement for the distant planet-like satellite.

Athena Coustenis and several colleagues from the Paris-Meudon Observatory presented the images at this weeks meeting of the International Astronomical Union in England. Already, the images have confirmed earlier observations of a brightly reflecting area near Titans equator, which many scientists say may be an indication of frozen methane on the moons surface.

Touted as some of the most detailed ground-based observations of Titan yet, the images will provide researchers with important information about the moon, in preparation for the arrival of the NASA/European Space Agency Cassini-Huygens probes, already en route to Saturn and Titan. Though a thick atmosphere obscures the moons surface, the Canada-France-Hawaii telescope was able to "see" infrared light coming from the surface.

Exploring Titan

Titan is the second-largest natural satellite in the solar system; only Jupiters moon Ganymede is larger. Planetary scientists say Titan is one of the solar systems most interesting moons because it is the only one known to have a substantial atmosphere. Yet although it was visited briefly by the Voyager 1 spacecraft, Titan remains largely unexplored.

Fortunately, a new set of science probes may turn that fact around. On October 15, 1997, NASA and the European Space Agency (ESA) launched the Cassini Oribter, a spacecraft that will study Saturn and several of its major satellites, including Titan, starting in 2004. Another probe, called Huygens, is getting a piggyback ride on Cassini, and will be plopped into Titans thick atmosphere, specifically for the purpose of analysis of this mysterious moon.

New images of Titans surface show its appearance at wavelengths of 1.3 (left) and 1.6 (right) microns.

Since it will be several years until these spacecraft get to their final destinations, planetary scientists must currently rely on Earth-based observations to study Titan. Though limited in scope, such observations made with both ground-based and space-based telescopes like the Hubble Space Telescope allow scientists to monitor several aspects of Titans surface and atmosphere.

Titanic ice mountains

One of the most difficult aspects of studying Titan lies in the fact that a dense layer of nitrogen obscures it. Because this atmosphere is so thick (its five times as dense as Earths nitrogen-rich atmosphere), direct observations of the moons surface are not easy to make.

In 1994, a group of scientists working with the Hubble Space Telescope first noticed the bright spot detected by Coustenis, a mysterious area roughly the size of Australia. After subsequent observations, some members of the team, including University of Arizona researcher Peter Smith, believed the bright spot might actually be a signature of a huge range of ice mountains.

"My favored picture of Titan's surface is an exotic place with methane-snow-covered mountains, a few hydrocarbon lakes, lots of water-ice chunks and some rocks."

"There is a lot of water ice on Titan, and at 90 degrees Kelvin (minus 298 degrees Fahrenheit), ice is as strong as granite so you can make big mountains out of it," said Smith. "I think what we see as the bright region is a very large range of ice mountains."

Others have suggested that the bright region may actually be the result of a large impact that carved away at Titans crust, uncovering a bright white layer of subsurface ice. But since detailed observations of the moon simply dont exist, a definitive explanation will have to wait until Cassini and Huygens arrive on the scene to gather more evidence.

Methane rain

Planetary scientists are also interested in Titan because a significant amount of methane is thought to be stored in the moons atmosphere and surface. In fact, some scientists think methane, which comprises about 10 percent of Titans atmosphere, may act like water on Earth, raining down on the moon, creating rivers, glaciers and even an ocean.

"My favored picture of Titan's surface is an exotic place with methane-snow-covered mountains, a few hydrocarbon lakes, lots of water-ice chunks and some rocks," said Coustenis.

Since Titan is 10 times further from the sun than Earth is (making it much, much colder), the question of life existing on this planet is theoretically impossible. But since organisms are known to exist at extremely cold temperatures on Earth, others say life is not out of the question. "Titan is very exciting because it has many similarities with our own planet," said Coustenis.

For now, researchers will have to keep guessing at what lies beneath Titans thick atmosphere until 2004, when Cassini and Huygens arrive.

"Theres good hope that we may be able to make a tremendous amount of progress both with the [Huygens] probe and with the Cassini orbiter," said Allison. "Theres no question that theyre going to represent an incredible quantitative and qualitative leap in what we know about the place."