(Inside Science) -- Enceladus, the sixth largest moon of Saturn, has a surface area about the size of Mexico and is mostly covered with ice. During a flyby mission in 2015, the Cassini spacecraft dove into a plume of spray shooting out of cracks near the moon's south polar region. Scientists have now analyzed the contents of the plume and found molecules that are a signature of deep-sea habitats on Earth that support microbes.

The group reports the results in a paper in the April 14 issue of the journal Science. They claim that the only plausible source for the particles detected in Enceladus' plume is hydrothermal reactions between hot rocks and water at the bottom of the moon's ocean. They detected the presence of molecular hydrogen and carbon dioxide, which together provide the ingredients necessary for methanogenesis -- a biochemical reaction crucial for the survival of microbes that live in the deep-sea regions on Earth. However, according to a commentary by Jeffrey Seewald, a geochemist at Woods Hole Oceanographic Institution in Massachusetts, scientists still have a long way to go before fully understanding the possibility for life underneath the ice of Enceladus.

The Cassini spacecraft, which launched in 1997, reached Saturn's orbit in 2004. It is now undertaking the final phase of a mission that started in December 2016 to explore Saturn's rings. The last flyby of the planet is scheduled for April 19. The project will end when the spacecraft falls into Saturn's atmosphere, probably around September of this year.