Saturn may officially be the best planet to search for life beyond Earth after NASA’s Cassini spacecraft discovered hot fluid vents on the Enceladean seafloor. Clouds of gas have erupted from Enceladus containing hydrogen, which has excited scientists as there are similar hydrothermal chemical reactions that occur at the ocean bottoms of the Earth.
Hydrothermal vents are filled with microbial life, suggesting that these icy moons away from Earth could be habitable. The evidence of hydrothermal systems does not prove the existence of life on Saturn, seeing as its environment could still be sterile. However, the findings are encouraging enough to re-examine the planet with superior instrumentation: technology that can sample the ejected water for evidence that biology does exist.
This is the most recent discovery made by Cassini, which is nearing the end of its mission after spending 13 years exploring Saturn, its rings and moons. On 22nd April, the spacecraft will begin a journey where it will travel between the planet and its rings for 22 orbits before it crashes into Saturn’s atmosphere in September.
“We’re pretty darn sure that the internal ocean of Enceladus is habitable and we need to go back and investigate it further,” commented Cassini scientist Dr Hunter Waite from the Southwest Research Institute in San Antonio, Texas.
“If there is no life there, why not? And if there is, all the better. But you certainly want to ask the question because it’s almost as equally as interesting if there is no life there, given the conditions,” he informed BBC News.
Cassini’s data also reveals levels of carbon dioxide, hydrogen and methane measured in the Enceladus plume were unbalanced. This could offer an energy source that organisms could rely on for food, according to a paper published on 13th April in the journal of Science.
“It indicates there is chemical potential to support microbial systems,” stated J. Hunter Waite Jr., program director for the space science and engineering division at the Southwest Research Institute in San Antonio – lead author of the Science paper.
In a different paper published on 13th April in the Astrophysical Journal Letters, another team of researchers successfully spotted what seems to be a similar plume rising from Europa, one of Jupiter’s large moons that also has an ocean beneath its icy exterior.
“The Cassini mission has really brought Enceladus to the fore in terms of the search for life elsewhere in the Solar System,” said British Cassini scientist Dr Andrew Coates.
“The top three now I would say are about equal. There’s Mars, which may have had life 3.8 billion years ago when conditions were very different to what they are now. There’s Europa, which has a subsurface ocean; and now Enceladus. Those three may have, or had, the right conditions for life.”
Dr Waite concluded: “For life, you need liquid water, organics, and the CHNOPS elements (carbon, hydrogen, nitrogen, oxygen, phosphorus, sulphur). OK, we haven’t yet measured phosphorus and sulphur at Enceladus. But you also need some kind of metabolic energy source, and the new Cassini results are an important contribution in that regard.”