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In the not-too-distant future, a spacecraft could deliver samples from an alien ocean to Earth, where scientists would scrutinize the material for signs of life.Scientists are developing a mission concept that would send a probe flying through the plume created by the 100-odd geysers erupting from the south polar region of Saturn's ice-covered moon Enceladus.These geysers blast water, salts and organic compounds from the satellite's subsurface ocean far out into space. The mission, known as Life Investigation for Enceladus (LIFE), would collect samples of this stuff, then send it winging back to Earth in a return capsule. [ Inside Enceladus, Icy Moon of Saturn (Infographic)] "Getting a sample from Enceladus would be phenomenal," said LIFE leader Peter Tsou, of Sample Exploration Systems in La Canada, California. "This 'are we alone' question — potentially we can shed tremendous light on it in a single mission."LIFE is not on NASA's books; it remains a concept at the moment. Tsou estimates the sample-return effort could be mounted for $700 million or so — about 30 percent the cost of NASA's Mars rover Curiositymission.Many astrobiologists regard the 310-mile-wide (500 kilometers) Enceladus and the much larger Jupiter moon Europaas the solar system's best bets to host life beyond Earth.Enceladus and Europa appear to possess subsurface oceans of liquid water that are in contact with their rocky mantles, making possible many complex chemical reactions. And recent studies suggest that, while both moons' oceans are beyond the reach of sunlight, they may still harbor energy sources sufficient to sustain microbial life.NASA is already working on a flyby mission to Europa, which the agency hopes to launch in the early to mid-2020s. But many scientists are also pushing for a dedicated Enceladus effort, in large part because of the satellite's dramatic geysers, which NASA's Saturn-orbiting Cassini spacecraft discovered in 2005.These powerful jets, which emanate from fractures near Enceladus' south pole, merge to form a plume — a frigid cloud of ocean particles that extends many miles into space, just waiting to be snagged and studied. [ See Enceladus' Geysers in Action (Video)]"It's free samples," Jonathan Lunine, of Cornell University, told Space.com. "We don't need to land, drill, melt or do anything like that."Cassini has flown through the plume on multiple occasions, finding evidence of carbon-containing organic compounds with its mass spectrometer instrument. But Cassini is not equipped to look for signs of life.The argument for sample return.Lunine is principal investigator of another mission concept called Enceladus Life Finder(ELF), which aims to search for signs of life in plume particles. But the ELF probe would do all this work onboard in the Saturn system, rather than send the samples back to Earth for analysis.Tsou thinks sample-return is a better way to go, saying that it may be tough for a robotic spacecraft millions of miles from its handlers to make a definitive detection of alien life."Right now, no biologist or astrobiologist has a generally agreed-upon definition of life," Tsou said. "So, in order for us to determine that there's life on Enceladus, it's not going to be a simple, binary, 1-or-0 answer," Tsou said. "You'll have to do many, many studies."As an example, Tsou and his team cite the protracted analysis of pieces of Comet Wild 2, which were delivered to Earth by NASA's Stardust missionin 2006. (Tsou served as Stardust's deputy principal investigator.)"Final confirmation of the cometary origin of the amino acid glycine from Comet Wild 2 was obtained over 3 years after the samples were returned to Earth," the LIFE team wrotein a paper presented at the 45th Lunar and Planetary Science Conference, which was held last year in The Woodlands, Texas."Significant advancement in assessing the biological potential of Enceladus can be made on returned samples in terrestrial laboratories, where the full power of state-of-the-art laboratory instrumentation and procedures can be utilized, without serious limits on power, mass or cost," they added. "Terrestrial laboratories provide the ultimate in analytical capability, adaptability, reproducibility, reliability and synergy amongst scientists." [ 5 Bold Claims of Alien Life] The LIFE probe would launch to Saturn orbit, which it could reach after 5 years if orbital dynamics allowed a speed-boosting flyby of Jupiter, Tsou said. The journey would take 7 or 8 years without such a gravity-assist maneuver, he added. (The trip would be much shorter, however, if NASA's in-development Space Launch System megarocket were used.)