June 14, 2012
Saturnian Moon Titan Has Tropical Lakes, Cassini Finds
Lee Rannals for redOrbit.com
NASA's Cassini spacecraft has discovered tropical lakes on Saturn's moon Titan, one of which is about half the size of Utah's Great Salt Lake.
Previous models had assumed the long-standing bodies of liquid only existed at the poles on the moon, but the latest findings published in this week's issue of the journal Nature shows the methane lakes in the "tropics" of Titan.
Caitlin Griffith, the paper's lead author, said that the liquid for these lakes likely came from an underground aquifer.
"In essence, Titan may have oases," Griffith, the Cassini team associated at the University of Arizona, Tucson, said in a press release.
Titan has a "methane" cycle, similar to Earth's hydrological cycle, and understanding this could help scientists learn more about the moon's weather. During the Saturn moon's cycle, ultraviolet light breaks apart methane, initiating a chain of organic chemical reactions.
However, scientists have been unable to account for how much methane is showing up on Titan.
"An aquifer could explain one of the puzzling questions about the existence of methane, which is continually depleted," Griffith said. "Methane is a progenitor of Titan's organic chemistry, which likely produces interesting molecules like amino acids, the building blocks of life."
When liquid methane falls to the surface on Titan, it forms the polar lakes. This is similar to Earth, where water is similarly transported by the circulation, but the oceans on our planet also transport water, helping to counter the atmospheric effects.
The latest results by Cassini detected the dark areas in the tropical region known as Shangri-La, which is close to the spot where the European Space Agency's Huygens probe landed in 2005.
When Huygens landed, the probe's lamp vaporized some methane from the ground, indicating it had landed in a damp area.
The areas appear dark to the visual and infrared mapping spectrometer on Cassini when liquid ethane or methane are present, according to NASA.
The tropical lakes detected by Cassini's visual and infrared spectrometer have remained in place since 2004. NASA said scientists have detected rain falling and evaporating in the equatorial regions, leaving them to believe the lakes could not be substantially replenished by rain.
"We had thought that Titan simply had extensive dunes at the equator and lakes at the poles, but now we know that Titan is more complex than we previously thought," Linda Spilker, the Cassini project scientist based at NASA's Jet Propulsion Laboratory, Pasadena, California, said in a press release. "Cassini still has multiple opportunities to fly by this moon going forward, so we can't wait to see how the details of this story fill out."