There's no argument: there are lakes filled with liquid methane on Saturn's moon Titan. But does that mean there's life in Titan's darkness and cold?
Scientists say the lakes seen in Cassini's July 2006 range from 3 to 70 km. (2 to 45 miles) in diameter. They are believed to be part of a "methane cycle" of evaporation, condensation, and precipitation, much like the water cycle on Earth.
Does this suggest there's life there?
Apart from Earth, Titan isn't the only place you'll find methane. You'll find it on Mars as well. Since methane has a relatively short life of a few hundred years, scientists are wondering what could be generating new supplies of it.
Some of the methane in Earth's atmosphere is produced by volcanic or tectonic activity, but most is created as a waste by-product of living things. So far, there's no evidence of recent volcanic or tectonic activity on either Titan or Mars.
Could underground microbial life be creating the methane?
We used to think life was only possible within a narrow range of temperature and chemicals. Now we know there are organisms extremophiles - living in extreme temperatures and in the total darkness of caves or deep waters, and living off simple inorganic compounds like iron and sulfur. Forms of anaerobic life - life that does not depend on oxygen exist deep within the Earth and even within "solid" rock. Scientists believe the mass of life, mainly bacteria, inside the Earth is much larger than the mass of life in and on and above the planet's crust.
Some of the most spectacular extremophiles are the more than 300 lifeforms thriving in scalding, acidic water around hydrothermal vents, fissures in the ocean floor. These lifeforms include thickets of giant tube worms, some more than a meter tall planted on the ocean floor, as well as bizarre species of mussels, shrimp, clams, and crabs. Some fissures even discharge white, flaky bacteria which obtain energy from hydrogen sulphide, not sunlight, along with water heated to as much as 400 degrees Celsius.. .
The methane lakes on Titan are especially intriguing because ice worms discovered on the floor of the Gulf of Mexico in 1997 ingest bacteria feeding off methane hydrate deposits in deep, dark, cold ocean depths.
"Dark" and "cold" sounds strangely like Titan.