Scientists at NASA have discovered further evidence suggesting conditions for life as we know it may exist on Saturn's ocean-bearing moon Enceladus.
The moon has captured the imagination of astronomers ever since NASA’s Cassini spacecraft delivered images showing massive plumes of vapour erupting from cracks on its icy surface.
Scientists believe there is an ocean of tidally heated liquid water beneath Enceladus' surface - making it a prime target in the search for extra-terrestrial life.
Cassini has been orbiting Saturn for nearly 13 years and will come to the end of its mission in September this year.
Latest findings
On its last deep dive past the moon in October 2015, the spacecraft measured the chemical composition of one of the vapour plumes using its Mass Spectrometer (INMS) instrument - which sniffs gases to determine their make-up.
In an article published this week in the Journal Science, NASA revealed that the plume was found to contain molecular hydrogen – a potential energy source for life.
The researchers believe the gas is pouring into the moon’s subsurface ocean through hydrothermal activity on the seafloor.
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.
The discovery means that microbes – if any exist there – could obtain energy by combining the hydrogen with carbon dioxide dissolved in the water.
“This is the closest we've come, so far, to identifying a place with some of the ingredients needed for a habitable environment,” said NASA administrator Thomas Zurbuchen.
Earth’s hydrothermal vents are thriving with microbial life – leading scientists to believe that the icy ocean world could be habitable.
The discovery makes Enceladus the only place - apart from Earth - where a local energy source for life has been discovered.
Candy store for microbes
"Enceladus is high on the list in the solar system for showing habitable conditions," said Hunter Waite, the lead author of the study."There is chemical potential to support microbial systems."
"Although we can't detect life, we've found that there's a food source there for it. It would be like a candy store for microbes."
Later this month, Cassini will begin a journey that will place it between Saturn and its rings for 22 orbits before its mission finally ends.
In September, the spacecraft will plunge into Saturn’s upper atmosphere, delivering its last images before it disintegrates on its final descent.
