From The National Geographic:
Instead of thriving on water, extraterrestrial organisms might live in a sea of liquid methane. Or instead of getting energy from the sun, they might thrive on hydrochloric acid. These possibilities could revolutionize future space missions in search of life elsewhere in the solar system, says the report, issued today by the National Academy of Sciences (NAS). The report concludes that scientists need to consider an expanded list of characteristics that define life, including so-called “weird” life-forms that may thrive where Earth organisms couldn’t.
Instead of dispatching spacecraft to dig into the subsurface of Mars, considered a prime candidate for primitive life because of its watery past, the report says the probes may have better luck on Saturn’s moon Titan, which has seas of liquid methane and ethane. In fact, the report concluded that Titan is the most likely candidate in the solar system for weird life. “It’s a carbon world, so there’s plenty of different kinds of carbon compounds there, and the possibility is that there may be the carbon compounds that make up life,” said John Baross, an oceanographer at Seattle’s University of Washington, who lead the report team.
More here.