WASHINGTON — Saturn's largest moon is the only body in the solar system besides Earth with lakes, leading scientists to compare it to this planet before life evolved.
A study in the current issue of the journal Nature said radar images from a NASA craft show the moon Titan has lakes of liquid methane and ethane. That suggests Titan, with a dense atmosphere like that of primordial Earth, also shares Earth's hydrological cycle of rainfall, formation of lakes and rivers, and evaporation, the study said.
Titan, which is bigger than the planet Mercury, has a thick atmosphere with thin nitrogen and methane cloud layers and is extremely cold: minus 290 degrees Fahrenheit. Even with the cold and the lack of life-sustaining oxygen, Titan resembles Earth before life developed here, study author Ellen R. Stofan said.
"It's too cold for water to be liquid on the surface of Titan, so I'm not convinced there was ever life there," said Stofan, a planetary geologist with Proxemy Research in Laytonsville, Md.
"But we know there was probably methane in the Earth's early atmosphere, so we have all the building blocks that were present when life evolved. This could help us understand ... the evolution of Earth."
Scientists had long suspected the presence of lakes or even seas of methane on Titan. This was confirmed with radar images that NASA's Cassini spacecraft sent from Titan on July 22.
Stofan said she hopes NASA will send a space vehicle to land on the shores of Titan's lakes to collect data and chemical samples.
"Here we are in the coldest reaches of the solar system, and we're looking at a landscape that looks like the lakes in Minnesota," Stofan said.
"I'm not predicting we'll find life. But we may find the chemical reactions that are the precursors of life."