The aptly named Titan has a handful of peers in the size department, but all orbit a different jovian planet.
| Scientists peer under Titan's
thick fog
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Europa Date of discovery: 1610
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CNN By Richard Stenger
(CNN) -- Taking a peek under the thick orange haze that enshrouds Titan, astronomers found a second, mysterious bright spot on the planet-sized moon.
Space and ground telescopes had earlier detected a large, vivid feature on the surface of the moon, which scientists speculated was a massive continent in an ocean of hydrocarbons.
Advanced optical techniques have allowed astronomers to take a closer look, revealing another such peculiarity, the European Space Agency announced this week.
"Another bright feature at Titan's Western limb was noticed for the first time," said Athena Coustenis, an astronomer at a Paris observatory.
The contrast between the bright spot and the darker areas around it "are compatible with a combination of organic deposits and ice extents, possibly related to topography," Coustenis added.
In other words, the finding gives a boost to the theory that Titan possesses landforms, possibly mountains, composed of frozen organic compounds.
The Saturn moon, larger in diameter than Mercury and Pluto, is thought to contain a rich soup of complex organic compounds like the primordial Earth.
What really lies underneath the opaque atmosphere could remain a mystery until an ESA robot craft plunges through the hydrocarbon smog in three years.
The Huygens probe is hitching a ride aboard NASA's Cassini spacecraft, which should arrive in orbit around Saturn in 2004 after an almost seven-year journey.
Months later, the Saturn orbiter will release Huygens, a suite of instruments packed in what resembles a large automobile hubcap, which will then parachute through the atmosphere and presumably land several hours later.
During the descent, the half-ton probe will study the organic makeup of the chemical fog, take photographs and keep an eye out for lightning. Huygens was designed to withstand such electrical outbursts, which are thought to take place on the moon.
Titan boasts an atmosphere, composed mostly of nitrogen and methane, ten times thicker than that on Earth. Scientists theorize that hydrocarbon rain and snow drizzle down to the surface.
The new Titan images were taken by the Canada-France-Hawaii observatory,
located on top of Mauna Kea, a dormant volcano on the island of Hawaii.
