Thaindian News

Washington, July 31 (IANS) Scientists have discovered a lake-like feature on Saturn’s satellite Titan, the second body in the solar system to posses a liquid surface, apart from the Earth. Astronomers detected the presence of the ethane lake with the help of the visual and infrared mapping spectrometer or VIMS, on board NASA’s Cassini orbiter.

The instrument, run by Arizona University (AU), identifies the chemical composition of objects by the way matter reflects light.

When VIMS observed the lake, named Ontario Lacus, it detected ethane, a simple hydrocarbon that Titan experts have long been searching for. The ethane is in liquid solution with methane, nitrogen and other low-molecular weight hydrocarbons.

“This is the first observation that really pins down that Titan has a surface lake filled with liquid,” VIMS principal investigator Robert H. Brown of AU’s Lunar and Planetary Lab said.

“Detection of liquid ethane in Ontario Lacus confirms a long-held idea that lakes and seas filled with methane and ethane exist on Titan,” said Larry Soderblom of the US Geological Survey.

The fact that the VIMS could detect the spectral signatures of ethane on the satellite’s dimly lit surface while viewing at a highly slanted angle through Titan’s thick atmosphere “raises expectations for exciting future lake discoveries by the infrared spectrometer”, said Soderblom, an interdisciplinary Cassini scientist.

The ubiquitous hydrocarbon haze in Titan’s atmosphere hinders the view to its surface. But there are transparent atmospheric “windows” at certain infrared light wavelengths through which Cassini’s VIMS can see the ground. VIMS observed Ontario Lacus on Cassini’s 38th close flyby of Titan in December 2007.

Infrared spectroscopy doesn’t tell the researchers how deep the lake is, other than it must be at least a centimetre or two deep, said Brown.

Brown and his team report their results in the July 31 issue of the journal Nature.