Incredible discovery on Saturn’s moon Enceladus
Researchers have made a discovery about Saturn’s moon that could end up changing everything we know about the universe.
If finding aliens in our Solar System was based on the roll of a dice, it just got a +1.
Researchers have found Saturn’s moon Enceladus has heat circulating beneath its icy crust, meaning the chemistry of biology is sustainable.
The space probe Cassini died a fiery death when it plunged into Saturn’s atmosphere in 2017. But its 13-year mission had gathered far more data than scientists could instantly analyse.
Oxford University, the Southwest Research Institute and the Planetary Science Institute have been sifting through the numbers to find statistical anomalies and significant patterns.
What they’ve found has prompted them to label Enceladus “a top contender for extraterrestrial life”.
It’s about heat. It’s about turning ice into water.
It’s about reacting minerals and molecules into the building blocks of life.
The study, published in the journal Science Advances, adds sustainability to the growing odds that Enceladus has a subsurface ocean filled with the complex hydrocarbons and phosphorus that sustain biology on Earth.
We know it can lead to life. Similar conditions to Enceladus can be found in deep ocean trenches, where the ‘hot soup’ surrounding volcanic vents is brimming with weird and extreme creatures.
Enceladus is about 150 million kilometres from the Sun. So the star’s rays are insufficient to warm its icy surface.
But the prevailing theory is that the gravity and magnetic fields of nearby Saturn are stressing Enceladus to the core.
Rock is being crunched into lava and that has melted the ice from beneath.
We know Enceladus has heat. It’s a highly active moon.
In 2005, Cassini detected dramatic plumes of ice being jetted off its surface and into orbit to create Saturn’s bright E-ring.
It was previously thought that this heat was patchy. Most had only been detected around the south pole.
Now, researchers have confirmed it is also in the north.
“Enceladus is a key target in the search for life outside the Earth, and understanding the long-term availability of its energy is key to determining whether it can support life,” says the study’s lead author, Dr Georgina Miles.
Life in the balance
Heat is important. Dissolved minerals are necessary. Organic chemistry is essential.
But it cannot add up to life without consistency.
Put simply, primordial goop needs to percolate for millions of years before the right combinations of stuff start to combine.
And just as life on Earth is dependent on the moods of the Sun, so too is life on Enceladus bound to Saturn and its other moons.
Earth must sit in a “Goldilocks Zone” where it is neither too hot nor too cold for liquid water to pool on the planet’s surface.
Enceladus must sit in a “Goldilocks Zone” where the spin-cycle stretching and squeezing of gravity from Saturn and the other moons creates the right amount of friction to sustain vast tracts of water beneath its icy surface. Too little, and the water will eventually freeze.
Too much, and the 500km diameter moon will turn into a hellscape – like Jupiter’s Io.
Researchers examined several years’ worth of surface temperature data collected by Cassini’s Composite InfraRed Spectrometer (CIRS). Then, they compared this to detailed modelling of what should be expected under various scenarios.
The upshot is that they found Enceladus’ North Pole to be seven times warmer than previously assessed – and the only available explanation for this is if heat is seeping upwards from a sub-surface ocean.
“This finding confirms that the icy moon is emitting far more heat than would be expected if it were simply a passive body, strengthening the case that it could support life,” the researchers write.
“The measured heat flow (46 ± 4 milliwatts per square metre) may sound small, but this is about two-thirds of the heat loss (per unit area) through the Earth’s continental crusts.”
And consistent heat is conducive to life.
One such example was revealed by a study from the University of Bremen, released last week.
It found unexpected biosignatures in a bright-blue volcanic sludge pulled from mud volcanoes near the Pacific Ocean’s Mariana Trench. The ooze was highly acidic – enough to burn skin on contact.
“It is simply exciting to obtain insights into such a microbial habitat because we suspect that primordial life could have originated at precisely such sites,” says University of Bremen geochemist Florence Schubotz.
“What is fascinating about these findings is that life under these extreme conditions, such as high pH and low organic carbon concentrations, is even possible.”
Building blocks assembled
The age of Saturn’s rings and moons is a mystery. It’s not a scientific failing. It’s because of the forensic challenge presented by icy surfaces that are constantly refreshing themselves.
Enceladus could be 150 million years young. Or 1 billion years old.
The Earth is approximately 4.5 billion years old.
So the more mature Enceladus is, having sustained subsurface heat helps the odds of something living being cooked up.
“This sub-surface ocean can only support life if it has a stable environment, with its energy losses and gains in balance,” the researchers say in a statement.
So, if life hasn’t yet evolved, chances are it still can. In the coming aeons.
“Understanding how much heat Enceladus is losing on a global level is crucial to knowing whether it can support life,” says study co-author Dr Carly Howett.
“It is really exciting that this new result supports Enceladus’ long-term sustainability, a crucial component for life to develop.”
The next challenge for researchers is to determine the actual age of the moon. And what lies beneath the surface.
The study estimates the ice sheet to be an average of 25 to 28km thick, thinning to about 20-23km at the north pole. Boring through the ice that far to collect samples would be an extremely challenging task.
So far, the best evidence has been collected by “sniffing” organic molecules in ice ejected from Enceladus’ ice shell.
Some of these sand-sized particles fall back to coat the moon’s surface. Others stay in orbit.
“Cassini was detecting samples from Enceladus all the time as it flew through Saturn’s E ring,” says Freie Universität Berlin researcher Dr Nozair Khawaja.
He was the lead researcher on another study, this time published by Nature Astronomy, released last month.
“We had already found many organic molecules in these ice grains, including precursors for amino acids,” he adds.
Assembling the data from Cassini’s many fly-bys in one place and deciphering its meaning has taken years of effort. But the pay-off is proof of fresh organic molecules in the ice grains.
These include aliphatic, (hetero)cyclic ester/alkenes, ethers/ethyl and, tentatively, nitrogen- and oxygen-bearing compounds.
That means these molecules are almost certainly from within Enceladus’ ocean, and not the result of different space-based chemistry.
Jamie Seidel is a freelance writer | @jamieseidel.bsky.social
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Originally published as Incredible discovery on Saturn’s moon Enceladus
