Incredible discovery on Saturn’s moon Enceladus may support life

In humanity’s search for proof of life in our solar system, the odds have just slightly improved, after researchers found Saturn’s moon Enceladus has heat circulating beneath its icy crust.

The space probe Cassini was destroyed in 2017, but its 13-year mission yielded masses of data before it plunged into Saturn’s atmosphere.

Since then, Oxford University, the Southwest Research Institute and the Planetary Science Institute have been analysing the data and what they’ve found prompted them to label Enceladus “a top contender for extraterrestrial* life”.

The study, published in the journal Science Advances, argues that Enceladus could have a sub-surface ocean filled with the complex hydrocarbons* and phosphorus* that sustain biology* on Earth.

Similar conditions to Enceladus can be found in Earth’s deep ocean trenches, where the “hot soup” surrounding volcanic vents brims with weird and wonderful creatures, some stranger than any science fiction.

Enceladus is about 150 million km from the sun, so the sun’s rays are insufficient to warm the icy surface of Saturn’s moon.

But the emerging theory is that the gravity and magnetic fields of Saturn are stressing Enceladus at the core, crunching rock into lava and melting the ice from beneath.

We know Enceladus has heat because it is a highly active moon.

In 2005, Cassini detected dramatic plumes of ice bursting off its surface and into orbit to create Saturn’s bright E-ring.

It was previously thought that this heat was patchy, as most plumes had only been detected around the planet’s south pole.

Now, researchers have confirmed sufficient heat 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,” said study lead author Dr Georgina Miles.

LIFE IN THE BALANCE
Heat is important, dissolved minerals are necessary and organic chemistry is essential – but none of that adds up to life without millions of years of consistency.

And just as life on Earth depends on 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 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 fire up like Jupiter’s Io, “the most volcanically active world in the solar system”, according to NASA.

Researchers examined several years’ worth of surface temperature data collected by Cassini’s Composite InfraRed Spectrometer (CIRS). They then compared the insights to detailed modelling of what would be expected under various scenarios.

They found Enceladus’ north pole was seven times warmer than previously assessed – and the only available hypothesis* was heat 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 measured heat flow … may sound small, but this is about two-thirds of the heat loss (per unit area) through the Earth’s continental crusts,” ,” the researchers said.

And consistent heat is conducive* to life, as confirmed by a study from the University of Bremen, released earlier this month.

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 Dr 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.”

ASSEMBLING BUILDING BLOCKS
The age of Saturn’s rings and moons remains a mystery – Enceladus could be 150 million years young or a billion years old.

The Earth is approximately 4.5 billion years old.

“This sub-surface ocean can only support life if it has a stable environment, with its energy losses and gains in balance,” the researchers said in a statement.

But even if life hasn’t yet evolved, it still could in the coming eons*.

“Understanding how much heat Enceladus is losing on a global level is crucial to knowing whether it can support life,” said 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 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 using organic molecules* in ice ejected from Enceladus’ ice shell.

Some of these sand-sized particles fall back to coat the moon’s surface, while others stay in orbit.

“Cassini was detecting samples from Enceladus all the time as it flew through Saturn’s E-ring,” said Free University of Berlin researcher Dr Nozair Khawaja, lead researcher of a separate study published by Nature Astronomy last month.

“We had already found many organic molecules in these ice grains, including precursors* for amino acids*,” he said.

POLL

GLOSSARY

• extraterrestrial: from outside Earth and its atmosphere, alien
• hydrocarbons: chemical combination of hydrogen and carbon, such as in oil or petrol
• phosphorus: poisonous chemical element that is usually yellowish-white or sometimes red or black in colour, shines in the dark and burns when in the air
• biology: scientific study of the natural processes of living things
• biosignatures: any substance or phenomenon that provides evidence for the existence of life.
• hypothesis: theory, an idea or explanation for something that is based on known facts but has not yet been proved
• primordial: existing at or since the beginning of the world or the universe
• microbial: relating to microbes
• habitat: the natural environment in which an animal or plant usually lives
• conducive: providing the right conditions for something to happen or exist
• molecules: the simplest unit of a chemical compound that can exist, consisting of two or more atoms held together by chemical bonds
• precursors: things happened or existed before other things, especially if had an influence on them
• amino acid: any of the chemical substances found in plants and animals that combine to make protein

EXTRA READING

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Black hole find challenges history

Force awakens beneath Saturn’s Death Star

QUICK QUIZ

1. How long was space probe Cassini’s mission before it was destroyed?
2. What’s special about Jupiter’s moon Io?
3. Approximately how old is Earth?
4. Enceladus is how many kilometres from the sun?
5. How many times warmer than previous assessments was Enceladus’ north pole found to be?

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CLASSROOM ACTIVITIES
1. Life on Saturn
What needs to exist for life to be habitable on another planet like Saturn?

Draw and label an informative scientific diagram on what scientifically needs to exist to sustain life.

Could Saturn meet these requirements?

Time: allow 20 minutes to complete this activity
Curriculum Links: English, Science, Personal and Social, Critical and Creative Thinking

2. Extension
Do you think we will in our lifetime see any living thing surviving on another planet?

If not in our lifetime, do you think sometime in the future? Explain your reasoning.

Time: allow 10 minutes to complete this activity
Curriculum Links: English, Science, Personal and Social, Critical and Creative Thinking

VCOP ACTIVITY
Grammar and VCOP
The glossary of terms helps you to understand and learn the ambitious vocabulary being used in the article. Can you use the words outlined in the glossary to create new sentences? Challenge yourself to include other VCOP (vocabulary, connectives, openers and punctuation) elements in your sentence/s. Have another look through the article, can you find any other Wow Words not outlined in the glossary?