We can find life on Enceladus without even landing

(ORDO NEWS) — Enceladus, a moon of Saturn, is one of the main extraterrestrial places in the solar system where life thrives.

It harbors a global salty ocean, where internal heating theoretically keeps the temperature acceptable for an alien marine ecosystem.

However, discovering this life is not so easy. The moon is surrounded by an icy shell that is estimated to be 5 kilometers (3.1 miles) thick at its thinnest point, and the ocean below it is 10 kilometers deep.

Here on Earth, that would be a pretty big problem, not to mention the moon, which is half the solar system away from us.

But we may not have to go to great lengths to drill into Enceladus’ shell.

A new study has found that we should be able to detect life on an icy moon in the plumes of salt water that erupt from its surface, even if there isn’t much life there.

“Obviously, sending a robot crawling through cracks in the ice and sinking deep into the seafloor will not be easy,” says evolutionary biologist Regis Ferrier at the University of Arizona.

“By simulating data that a more trained and advanced orbiting spacecraft would collect from plumes alone, our team has now shown that this approach will be sufficient to determine with certainty whether there is life in Enceladus’s ocean, even though there is actually no need to explore depths. the moon. It’s an exciting prospect.”

Enceladus is very different from Earth; it is unlikely to be teeming with cows and butterflies. But deep under the earth’s ocean, far from the life-giving sunlight, another type of ecosystem has arisen.

Life, clustered around vents at the bottom of the ocean that spewing heat and chemicals, does not depend on photosynthesis, but on harnessing the energy of chemical reactions.

What we know about Enceladus suggests that similar ecosystems may be lurking on its seafloor. It orbits Saturn every 32.9 hours, traveling on an elliptical path that curves the Moon‘s interior, generating enough heat to keep the water closest to the core liquid.

It’s not just a theory: at the south pole, where the icy shell is thinnest, gigantic pillars of water hundreds of kilometers high have been seen erupting from under the ice, spewing water that scientists believe contributes to the formation of ice on Saturn’s surface. rings.

When Saturn’s Cassini probe flew through these plumes more than a decade ago, it detected several curious molecules, including a high concentration of a compound associated with Earth’s hydrothermal vents: methane and smaller amounts of dihydrogen and carbon dioxide.

They may be related to the methane-producing archaea here on Earth.

“On our planet, hydrothermal vents are teeming with life, big and small, despite the darkness and insane pressure,” Ferrier said. “The simplest living things are microbes called methanogens, which feed on energy even in the absence of sunlight.”

Methanogens metabolize dihydrogen and carbon dioxide, releasing methane as a by-product. Ferrier and colleagues modeled the methanogenic biomass that we might expect to find on Enceladus if biomass existed around hydrothermal vents like those on Earth.

They then modeled the likelihood that cells and other biological molecules would be ejected through the vents and how much of these materials we were likely to find.

“We were surprised to find that a hypothetical number of cells would equal the biomass of just one whale in the global ocean of Enceladus,” says evolutionary biologist Antonin Affholder, who is now at the University of Arizona but at the time of the study worked at the Paris University of Science and Letters in France. .

“The biosphere of Enceladus can be very sparse. Yet our models show that it would be productive to feed the plumes with enough organic molecules or cells to be detected by instruments aboard future spacecraft.”

Equipped with the expected abundance of these compounds, an orbiting spacecraft may be able to detect them – if it could make several passes of the plume to collect enough material.

Even then, there may not be enough biological material, and the likelihood of a cell being able to survive the journey through the ice and be ejected into space is probably quite small.

In the absence of such a smoking gun, the team suggests that amino acids such as glycine will serve as an alternative, indirect signature if the amount exceeds a certain threshold.

“Given that, according to calculations, any life on Enceladus will be extremely rare, there is still a good chance that we will never find enough organic molecules in the plumes to definitively conclude that it is there,” Ferrier says.

“So instead of focusing on the question of how much is enough to prove the existence of life, we asked, ‘What is the maximum amount of organic material that can be present in the absence of life?’

These numbers, the researchers say, could help develop future missions in the coming years. In the meantime, we’ll just be here on Earth wondering what an ecosystem deep under the ocean might be like on a moon orbiting Saturn.


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