The search for extraterrestrial life outside our own planet has been a long one, with still no definite results. There have been a few possible positives, such as the ALH84001 Meteorite, which has magnetite structures suggesting there was biological activity on Mars sometime in the distant past, and may also be the host to several fossils of micro-organisms (though that’s disputed). However, thus far there’s been nothing definite.

That’s really to be expected, however. We’ve probed only a tiny corner of our own solar system, much less our galaxy. As a species, we’ve only managed to send humans to the moon a few times, and have only sent robots and probes to do superficial examinations of a few other planets, and occasionally their moons.

The Cassini is one such probe, launched in 1997 with a specific destination: the moons of Saturn. It arrived in 2004 after a long and somewhat roundabout journey, and has been used to make observations of the Saturn system ever since. Thanks to Cassini and its attached lander Huygens, we know much more about Saturn and its moons than we did even ten years ago.

Cassini has already made remarkable progress, being the instrument for the discovery of three new moons, the depositing of a lander on Titan (Saturn’s largest moon), and what may ultimately turn out to be its most important discovery: the Plumes of Enceladus.

Enceladus is one of Saturn’s smaller moons, and is completely covered in ice. It was previously assumed that the ice was solid, but Cassini discovered that there were massive liquid geysers shooting up from beneath the ice, jettisoning water away from the surface and into the depths of space. This showed that there was a liquid ocean somewhere beneath that thick icy crust, and brought new excitement over the strange little moon--that it might be the host to extraterrestrial life.When Cassini did a close flyby of the moon in 2008, it passed directly through one of these plumes, collecting samples. It was discovered that they weren’t just water; they also contained hydrocarbons necessary for life on earth, as well as what may well be biological compounds.

Unfortunately, Cassini’s mission is set to end late next year, with the probe entering into Saturn’s atmosphere for destruction. With the loss of our greatest source of information in the Saturn system imminent, some scientists are scrambling for another probe to be sent to closer study Enceladus specifically.

“It would be a test of one of the ideas about the origin of life,” said Carolyn Porco, the head of the imaging team for the Cassini mission, and one of the greatest proponents for a second mission to focus on searching for life on Saturn’s moons, and on Enceladus in particular.

However, just getting the spacecraft funded and off the ground isn’t necessarily the hard part. It’s an enormously complicated problem, and scientists are still in debate over how exactly to search for life with the limited resources available. More probes could pass through the plumes and do a finer chemical analysis, but it’d be difficult for them to differentiate between true life and naturally-formed biological molecules (such as amino acids).

But if such a mission were successful, it would mean so much for us. It would be a huge leap forward in terms of space exploration, and it would answer so many questions we have about the nature of biological life and how it arose.