Fog discovered on Saturn's moon Titan

Washington, December 19 (ANI): Scientists have found evidence for the presence of fog on Saturn's moon Titan.

Planetary astronomer Mike Brown of the California Institute of Technology, 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.

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.

The VIMS instrument provides "hyperspectral" imaging, covering a large swath of the visible and infrared spectrum.

Brown and his colleagues, including Caltech undergraduate students Alex Smith and Clare Chen, who were working with Brown as part of a Summer Undergraduate Research Fellowship (SURF) project, searched public online archives to find all Cassini data collected over the moon's south pole from October 2006 through March 2007.

They filtered the data to separate out features occurring at different depths in the atmosphere, ranging from 20 kilometers (12.4 miles) to .25 kilometers (820 feet) above the surface.

Using other filters, they homed in on "bright" features caused by the scattering of light off small particles, such as the methane droplets present in clouds.

In this way, they isolated clouds located about 750 meters (less than a half-mile) above the ground.

These clouds did not extend into the higher altitudes-into the moon's troposphere, where regular clouds form.

In other words, according to Brown, they had found fog.

"Fog-or clouds, or dew, or condensation in general-can form whenever air reaches about 100 percent humidity," Brown said.

"There are two ways to get there. The first is obvious: add water (on Earth) or methane (on Titan) to the surrounding air. The second is much more common: make the air colder so it can hold less water (or liquid methane), and all of that excess needs to condense," he added.

The only possible way to make Titanian fog is to add humidity to the air, and the only way to do that, according to Brown, is by evaporating liquid-in this case, methane, the most common hydrocarbon on the moon, which exists in solid, liquid, and gaseous forms.

Brown notes that evaporating methane on Titan "means it must have rained, and rain means streams and pools and erosion and geology.

The presence of fog on Titan proves, for the first time, that the moon has a currently active methane hydrological cycle." (ANI)