Sen— A daring mission to swoop through ice-geysers erupting from one of Saturn's moons in a bid to look for life is being proposed to NASA.
The probe would be sent to capture samples of the spray from Enceladus and to bring them back to Earth frozen and intact so that they can be examined by astrobiologists.
Scientists say the mission, dubbed LIFE (Life Investigation For Enceladus), would be a low-cost one, but needs to be sent by 2019 to allow Jupiter's gravity to help speed the probe on its way with a slingshot effect.
Thanks to NASA's Cassini probe orbiting Saturn, the plumes of icy particles are known to contain water, organic compounds and dust which constantly feed into one of the planet's spectacular system of rings, the E ring.
Cassini's cosmic dust analyser found that the geysers are bursting from fissures known as tiger stripes that run across the 505 km wide (314 miles) moon and that they have a composition rather like sea water.
Enceladus has been established by NASA as one of three prime targets to examine for life, along with Saturn's largest moon Titan and one of Jupiter's big four moons, Europa.
A team led by Peter Tsou, has spent some years planning LIFE. He appealed for the sample return mission to get the green light from NASA at the annual autumn meeting of the American Geophysical Union in San Francisco this week.
The "tiger stripes" fissures of Enceladus imaged from Cassini. Credit: NASA/JPL/Space Science Institute
He says it could operate in a similar way to NASA's STARDUST mission which flew through the jets from Comet Wild 2, capturing samples with an aerogel screen that it then returned to Earth in 2006 for analysis along with interstellar dust that it had collected on the way.
Cassini found that the ice spray from Enceladus is likely to come from an underground saltwater lake or ocean of water that is kept liquid by the gravitational forces in Saturn's moon system. Planetary scientists are intrigued to discover whether that liquid water could contain simple aquatic life.
Astrobiologist Dr Lewis Dartnell, of the Centre for Planetary Sciences at University College London/Birkbeck, told Sen: "The tiny snowball moon Enceladus, with it’s watery underground environment, is a very exciting prospect for the potential for life beyond our Earth.
"And with Enceladus spurting it’s subsurface water into outer space it’s almost like we get a sample for free – all of the science with none of the hassle of needing to land or drill through kilometers of ice.”
Tsou says that although the Saturn E ring has been generated and sustained by the jets from Enceladus for at least 300 years, it cannot be known how long the eruption will continue, making a mission urgent. He proposes it be part of NASA's Discovery programme with mission costs capped at around $425 million.
It is far cheaper than a proposal for a $2.5 billion mission to explore Saturn, Enceladus and Titan that had been proposed by NASA and ESA but which was passed over in 2009 in favour of another mission to Jupiter.
Tsou's paper proposing the mission says: "Sample return missions are missions that continually yield results long after the design efforts have ceased and the samples have been returned. LIFE can make similarly important findings and profound scientific contributions to astrobiology in the outer planets as STARDUST did in Kuiper belt objects and the Solar System formational process."