Enceladus has fast progressed from being simply another little Saturnian moon to prime ground for answering the fundamental question: are we alone in the universe? No one believes Enceladus could harbour intelligent life, but if it does, it would provide compelling proof that life is abundant and that, given the chance, it will "find a way."
A large range of elements are required to keep a human alive, yet only five are required by all living things on Earth: hydrogen, oxygen, carbon, nitrogen, and phosphorus. The fact that Enceladus possesses an ocean of liquid water, some of which is escaping into space, is what first drew astrobiologists' attention to the small moon, so we know the first two elements on the list are plenty.
The presence of ammonia and methane ices in the moon's plumes confirms the presence of nitrogen and carbon in Enceladus' interior ocean, while the availability of biologically accessible energy is indicated by molecular hydrogen. However, there have been concerns raised concerning phosphorus. Although alternate routes to life may exist, the odds for self-replicating organisms would be significantly reduced in the absence of phosphorus. However, according to a report published in the Proceedings of the National Academy of Sciences, phosphorus insufficiency is unlikely to be a concern.
"In the years since NASA's Cassini spacecraft visited the Saturn system, we have been repeatedly blown away by the discoveries made possible by the collected data," Southwest Research Institute's Dr. Christopher Glein stated in a statement.
Although we've known about Europa's interior ocean for considerably longer than Enceladus', we know more about Saturn's moon's composition than Jupiter's. This is because we've had the opportunity to study the plume emitted by Enceladus' geysers.
"What we've discovered is that the plume contains practically all of the fundamental prerequisites of life as we know it," Glein explained. The exception is phosphorus, which has no direct evidence of its presence.
Because future missions with the sensitivity to test for the existence of phosphorus are still a long way off, Glein and co-authors found a less direct route to establish its presence.
Enceladus is not completely submerged. We know from its density that it has a solid core that nearly definitely contains all of the plentiful elements in the cosmos, including phosphorus. The article simulates the interactions between the core and the ocean above to see if phosphate minerals in the rocks are released into the ocean. They discovered that the temperature, pressure, and acidity were optimal for making phosphates especially soluble, primarily in the form of orthophosphate (PO43).
Enceladus' core phosphorus should dissolve in its ocean to support life. Southwest Research Institute is the source of this image.
"The underlying geochemistry has an elegant simplicity that makes the presence of dissolved phosphorus unavoidable," Glein remarked.
This does not necessarily imply that Enceladus is populated, but it is likely habitable; we could probably seed it if we so desired. An absence, then, signifies that life isn't as easy to appear, and its presence isn't unavoidable on suitable worlds.
"We need to get back to Enceladus to see if a habitable ocean is indeed populated," Glein says unequivocally.
The paper appears in the Proceedings of the National Academy of Sciences.