An environment that some scientists believe led to life on Earth has been found on Saturn’s ocean-bearing moon Enceladus, NASA scientists have said.
A discovery of molecular hydrogen was made in October 2015 – but has only now come to light – when NASA’s Cassini spacecraft took samples as it passed 30 miles (49 km) above the moon’s southern pole.
Hydrogen molecules were detected in vapour plumes emerging from cracks in Enceladus’ surface.
Such conditions occur when hot rocks meet ocean water, and may have led to the beginning of microbial life on Earth more than four billion years ago.
They are said to make Enceladus the only place apart from Earth where a potential energy source for life has been found.
Enceladus is high on the list in the solar system for showing habitable conditions, said lead author Hunter Waite.
The findings, published in the journal Science, indicate there is chemical potential to support microbial systems, he added.
We’re pushing the frontiers. We’re finding new environments, said NASA’s Planetary Science Division director, James Green.
We’re looking in a way that we never thought possible before for environments in our solar system which may harbour life today.
Previous discoveries include geysers which shoot hundreds of miles into space from Enceladus – some of the material falling back onto the surface as a coat of ice.
A vast ocean – believed to be the source of the geysers – is said to be buried between 19 and 25 miles (30-40 km) beneath Enceladus’ icy shell.
Cassini will end a 13-year mission exploring Saturn and its moons in September.