The largest body may be about the size of the Caspian Sea. Before now, Cassini had only caught glimpses of smaller lakes on Titan, which is about 50 percent larger than Earth’s moon. But scientists had suspected that Titan might contain larger bodies of liquid methane, because of evidence of methane in the moon’s atmosphere.
Methane is a gas on Earth, but a liquid on Titan because of the moon’s cold temperatures — its surface temperature is around -290 degrees Fahrenheit — and atmospheric pressure.
“We’ve long hypothesized about oceans on Titan and now with multiple instruments we have a first indication of seas that dwarf the lakes seen previously,” said Cassini scientist Jonathan Lunine of the University of Arizona in a press statement.
Cassini’s radar imaged several dark areas near Titan’s North Pole. Although no definitive proof exists that those areas are indeed liquid, their shape, smooth surface and other properties suggest that they are. The radar has glimpsed only a portion of each of the areas, so it’s impossible to know their full size, but the largest feature is at least 39,000 square miles.
Meanwhile, Cassini’s visual imaging cameras, which photograph the entire surface of Titan, have captured pictures of a much larger dark feature, the northern end of which corresponds to the radar images that suggest liquid. If the entire area captured in the pictures is a sea, Cassini scientists said, it would be about the size of Earth’s Caspian Sea.
In order to find out, scientists are repositioning Cassini’s radar instruments so that, in May, they will pass directly over the larger dark areas seen in the visual images.
Cassini — a joint project of NASA, the European Space Agency and the Italian Space Agency to study Saturn and its moons — launched in 1997 and reached Saturn in 2004.