NASA's Cassini spacecraft sent back images from Saturn's giant moon and scientists are almost sure the black patches near the pole are lakes. They think the dark patches could have been caused by Cassini's radar beam hitting very smooth surfaces, most probably liquid methane or ethane, on Titan's surface.

If the scientists are right, Titan is only the second body known to have liquid surfaces. The lakes are thought to be filled by rainfall and even seasonal storms, which are part of Titan's methane cycle.

The largest lakes are around 62 miles (100 km) across, although there is also a network of smaller, interconnected lakes said to resemble parts of Finland and Canada. Some appear to be deposits left behind as the methane lake evaporated. The lakes are more common near the pole probably because the temperature is cooler and the methane is less likely to evaporate. But since the temperature differences are small, lakes may exist at lower latitudes.

"When we have more coverage of the equator, we could see lakes there, too. We've only covered a few per cent of the surface so far," says Enrico Flamini of the Italian Space Agency in Rome.

"We could hope to see sea-surface textures due to waves diffracting around islands, or vortices in the wake of islands," says Cassini radar scientist Ralph Lorenz of the University of Arizona, US. "These sort of dynamic features would make liquids 'come alive'." While evidence of lakes is strong, the patches could turn out to be areas of soot, or dry lake beds. Imaging the areas again could show if the lakes grow or shrink or have waves.

Recent images taken by the Cassini spacecraft indicates that the highlands of Saturn's moon Titan may be riddled with caves.

The  Xanadu region of Titan is about 4000 kilometers (about 2500 miles) wide. While already though to be a highland area, Cassini's haze-penetrating radar shows that  the interior of the region is crossed by mountain ranges rising to a height of 1,000 meters (about 3,000 feet)  This contrasts with most of Titan's surface, which appears relatively flat.

"These are the highest mountains measured on Titan so far," says Cassini team member Ralph Lorenz of the University of Arizona in Tucson.

Radio waves bouncing off Xanadu indicate these mountains are not solid. They appear to have strange electrical properties – specifically a low "dielectric constant," which means they shouldn't be solid enough to stand.

"The only reasonable material makeup that could have a very low dielectric constant and still hold together enough to form the structures that we see would be some sort of porous stuff – most likely porous water ice," says another team member, Steve Wall of the NASA JPL in  Pasadena, California.

One theory is that the region is filled with caverns, possible carved out by the methane rain that is believed to fall on Titan.

Erosion from that rain would also form the long river valleys along the Xanadu region's edge. Cassini scientists theorize that these rivers carry ice grains down to the plains to form the dunes seen on much of Titan's surface.

There are also small, dark patches in this region. These may be methane lakes, although there little evidence of liquid still present on the surface. Evidence of liquid may be forthcoming, however.  This weekend, Cassini will take pictures of Titan's north pole, where lakes or seas to would be likely to exist, since the extreme cold would keep methane from evaporating into gaseous form.

You can view a Quicktime video of the the Cassini images here.

NASA's Earth Observing-1 spacecraft was designed to test imaging technology and collect large amounts of data, also filtering the information it collects to discard those that need not be downlinked to earth. The Autonomous Sciencecraft software ensures that scientists on Earth only receive the important data.

According to Steve Chien, principal investigator at NASA's Jet Propulsion Laboratory, ever since the decision-making software has been used on EO-1 last year, scientists are 100 times more likely to receive data that actually has valuable information for flood monitoring and for looking at freezing and thawing patterns.

Another benefit of the software is that it has reduced mission costs from $3.6M per year to $1.6M per year.

Because of the benefits the implementation of the Autonomous Sciencecraft has rendered, Onboard Autonomous Science Investigation System principle investigator Rebecca Castano hopes the software can also filter data being collected by the Mars rovers and Mars Odyssey missions.

The same software may help home in on rare and seasonal Mars events such as dust devils and cloud dusts. It will also increase to 90% the rover's success rate of finding a rock worthy of study.

Autonomous Sciencecraft can also aid future study of Saturn's moon Titan. According to Ralph Lorenz, an assistant research scientist at the Lunar and Planetary Laboratory at the University of Arizona, since Titan is so far away from Earth, communications with an aircraft will be extremely difficult. But the software "could help position whatever aircraft would be used, such as some sort of hot air balloon-type device, in an area likely to produce profitable samples."