Scientists believe life could exist on Saturn’s moon Enceladus around hydrothermal vents which are similar to those found at the bottom of the Earth’s ocean.
The “exciting” discovery was made after the space probe Cassini flew through spray bursting from the moon’s cracked icy surface.
Chemical analysis of the plume suggested conditions favourable for methanogenesis – the generation of methane by microbes that use hydrogen and carbon dioxide to obtain energy.
Here on Earth, methane-making bugs flourish in the vicinity of hydrothermal vents, fissures in the ocean floor that gush water heated by volcanic activity.
The levels of hydrogen on Enceladus were high enough to imply a continual source, and were consistent with hydrothermal activity.
The moon, which is 502 kilometres (312 miles) across, is one of many orbiting Saturn. It has a rocky interior and icy surface with what is believed to be a salty ocean sandwiched between the two. Tidal heating caused by the moon’s interaction with Saturn’s powerful gravity prevents the ocean from freezing.
Writing in the journal Science, the US team led by Dr Hunter Waite, from the Southwest Research Institute in San Antonio, Texas, concluded: “Our analysis supports the feasibility of methanogenesis as an energy-releasing process that can occur over a wide range of geochemical conditions plausible for Enceladus’ ocean.”
Leading British expert Professor Andrew Coates, from University College London, said: “This is an exciting and remarkable result which shows that Enceladus may actually be habitable.
“We know that the four requirements for life as we know it are liquid water, the right chemistry, a source of energy and enough time for life to develop.
“But now, we know that three of the four conditions are there on Enceladus – and this distant moon now joins Mars and Europa as the best potential locations for life beyond Earth in our solar system.”
However the scientists did point out that just because Enceladus has conditions suitable for methanogenesis, that does not prove anything is actually living there.