Washington, Dec 19 (IANS) Saturn’s largest moon, Titan, looks to be the only place in the solar system - aside from our planet, with copious quantities of liquid, largely liquid methane and ethane, on its surface.
Earth and Titan share yet another feature, which is inextricably linked with that surface liquid - common fog.

According to planetary astronomer Mike Brown of the California Institute of Technology (Caltech), the presence of fog provides the first direct evidence for the exchange of material between the surface and the atmosphere, and thus of an active hydrological cycle, which previously had only been known to exist on earth.

Brown, professor of planetary astronomy at Caltech, details evidence that Titan’s south pole is spotted “more or less everywhere” with puddles of methane that give rise to sporadic layers of fog. Technically, fog is just a cloud or bank of clouds that touch the ground.

The researchers made their discovery using data from the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft, which has been observing Saturn’s system for the past five years.

“Fog - or clouds, or dew, or condensation in general - can form whenever air reaches about 100 percent humidity,” Brown says, according to a Caltech release.

These findings were presented Friday at the American Geophysical Union’s 2009 Fall Meeting in San Francisco and also published in The Astrophysical Journal Letters.