NASA's Cassini spacecraft has spotted methane lakes in the so-called "tropics" of Saturn's moon, Titan. (Where temperatures reach a balmy −179 °C, or −290 °F.) The lakes were a bit of a surprise to researchers who had assumed that the long-standing liquid bodies would only exist at the poles. The discovery also raises the unique possibility that life could exist in this bizarre environment.


Top image: Ron Miller, who wants to call this "Lake Bonestell" after famous Titan artist Chesley Bonestell.

To make this discovery, researchers used Cassini's visual and infrared mapping spectrometer, which detected the dark areas in the tropical region known as Shangri-La — an area very close to the spot where the European Space Agency's Huygens probe landed in 2005. After Huygens had landed, the heat from its lamp vaporized some methane from the ground, giving researchers a good idea that it settled in moist area.


One of the tropical lakes appears to be the size of Utah's Great Salt Lake, and features a depth of at least three feet (one meter). NASA made the announcement of the liquid lakes, as part of their ongoing Cassini mission.

The question now facing the researchers is, where did the liquid for these lakes come from? Caitlin Griffith, a Cassini team associate at the University of Arizona, speculates that the lake is being fed from an underground aquifer. "In essence," she says, "Titan may have oases."

It's important that scientists study these lakes, so that they can get a better handle on Titan's weather. While the Earth has a "hydrological cycle," Titan has a "methane" cycle, with methane rather than water circulating. Ultraviolet light is able to pierce through Titan's atmosphere, causing it to break the methane apart on contact. This results in a complicated chain of organic chemical reactions.

It's the aquifer theory, therefore, that supports the idea that there's a subterranean source for the continuous replenishment of methane. And because it rains so infrequently on Titan, there's no way that precipitation could account for the large, waist-deep lakes of continually evaporating methane.


What's of particular interest to the researchers are the organic chemical reactions that are likely producing interesting molecules such as amino acids, the building blocks of life. As a result of this finding, astrobiologists cannot rule out the possibility that Titan might be able to spark and harbour primitive lifeforms.

NASA's findings will appear in an upcoming issue of the journal Nature.

Image via NASA.