One of Saturn‘s moons could harbour alient life, scientists say – but don’t expect a call from ET any time soon.
Life in this case means micro-organisms in oceans deep beneath Enceladus’s frozen surface.
Scientists discovered that certain types of micro-organisms can not only survive but thrive in the inhospitable conditions of the planet’s sixth-largest moon.
In a laboratory, researchers recreated the conditions of Enceladus’ subsurface oceans and introduced bacteria that normally live on deep-sea hydrothermal vents.
They thought that with almost no oxygen, high concentrations of dissolved carbon dioxide and an extremely alkaline pH, the ocean would be hostile to life.
However, they were shocked to find that these hardy microbes tolerated the alien conditions far better than previously thought possible.
According to the researchers, this raises the probability that life will one day be found on Saturn’s moon.
Dr Nozair Khawaja, of the Freie Universitat Berlin and co-author of the study, said: ‘This was really a surprise to us. This was an experiment for which we did not expect such a successful outcome.’
Saturn’s moon Enceladus (artist’s impression) could harbour alien life in oceans deep beneath its frozen surface, according to a new studyÂ
Scientists found that a type of bacteria that normally lives in deep–ocean hydrothermal vents can not only survive, but thrive in a laboratory simulation of Enceladus’ oceanÂ
Enceladus has a diameter of around 310 miles (500km) – about as wide as Arizona.
On the surface, conditions are exceptionally cold, with temperatures as low as –201°C (–330°F).
But despite its barren, icy surface, scientists believe that it is one of the most promising places in our solar system to look for extraterrestrial life.
This is because geothermal processes deep near its rocky core produce enough heat to maintain large oceans of liquid water beneath the surface.
Near the south pole, plumes of ocean water erupt through cracks in the crust, shooting ice particles hundreds of miles out into space.
NASA’s Cassini probe flew through these plumes on multiple occasions, gathering samples and analysing their chemical composition.
This revealed signs of hydrothermal processes on the seafloor, which could be key to sustaining life, alongside the organic chemicals that could provide the building blocks of amino acids and proteins.
Now, scientists have the first concrete evidence that life can thrive in these hostile oceans.
Although surface temperatures can be as low as –201°C (–330°F), geothermal activity near the rocky core maintains a vast ocean of liquid water where life could developÂ
In the laboratory simulation, scientists tested a type of bacteria called Methanothermococcus okinawensis, which has an incredible natural ability to survive without oxygen.
Instead, its metabolism runs on carbon dioxide and hydrogen released by the geologically active rocks of deep ocean vents.
Co–author Professor Frank Postberg, a planetary scientist at Freie Universität Berlin, told the Daily Mail: ‘On early Earth there was no oxygen either, and these ancient microbes have developed under these conditions.’
Previously, scientists had thought that the high pH of Enceladus’ ocean was unsuitable for them, but the laboratory tests showed that they are more than happy to grow in these tough conditions.
In the laboratory tests, they were even able to adapt their metabolism to the low amounts of carbon dioxide.
Professor Postberg said this shows that life ‘could’ survive on Enceladus, but added ‘it is by no means certain that it actually does!’
The good news is that, in a separate paper also published today, Professor Postberg shows that signs of life may be much easier to find than previously thought.
Droplets of the ocean are ejected from Enceladus’ south pole when bubbles filled with gas rise to the surface and pop.
Scientists have been able to directly sample water from Enceladus’ sub–-surface oceans by collecting particles of ice ejected into space through cracks in the South Pole (pictured)
Researchers say the fact that these droplets freeze slowly means that some chemicals are concentrated into a few locations (shown in red). This would make it easier for spacecraft to detect any chemical signs of lifeÂ
Water vapour then carries these droplets through cracks in the ice shell and out into space at speeds up to 620 miles per hour (1,000km/h), where scientists assumed they would instantly freeze.
However, new modelling and laboratory tests show that these droplets actually freeze quite slowly.
During this gradual process, most components in the water are separated, concentrating salts and other minerals into different locations inside the droplet.
If one of these frozen drops shatters on its way out, the result will be tiny fragments containing a highly concentrated sample of just one substance.
That natural process will be particularly helpful if scientists want to hunt for the subtle chemical signatures of life beneath the ocean.
‘Enceladus actually does a lot of the work for us in preparing samples for analysis that usually take a lot of effort in chemical labs on Earth,’ said Dr Postberg.
If a droplet did contain the chemical ‘biosignature of life’, the freezing and shattering process could create tiny ice particles with a high concentration of these chemicals in a relatively pure form.
That would make any biosignatures significantly easier to spot, even with the level of technology currently available.
None of this means that Enceladus does harbour life, but if there is life, Professor Postberg said ‘we now have a good chance to detect it’.
He added: ‘We should go back there and find out.’
