Finding life on Saturn’s moon Enceladus may be easier than we thought

By | December 21, 2023

New research suggests there are locations on the surface of Saturn’s moon, Enceladus, where spacecraft could land to scoop up pristine traces of the key ingredients for life. These biosignatures are believed to originate from subsurface oceans in the icy shell of the world.

Enceladus It has long been known to harbor organic molecules – compounds made up of carbon, oxygen and nitrogen – in its subsurface oceans. Before it crashed to the surface Saturn in 2017, the Cassini spacecraft flew through plumes of material erupting through fissures in the surface of Enceladus, detecting organic molecules such as methane and ethane, as well as other complex compounds reaching enormous heights.

About 90% of the larger grains in this material, launched thousands of miles above Enceladus, don’t actually escape the Saturnian system. Instead, they fall back to the surface of Saturn’s moon, scientists now say, where they could theoretically be collected and examined by spacecraft.

‘We can learn a lot about potential biosignatures in Enceladus’ ocean by sending a mission to the surface of Enceladus. It was previously thought that to sample the freshest material from the Enceladus ocean, you had to fly through the plume and take measurements. plume grains and gases,” Amanda R. Hendrix, a senior scientist at the Planetary Science Institute and research leader, said in a statement. “But now we know that you can land on the surface and be confident that your instruments can measure relatively pristine plume organic matter – sourced from the ocean.”

Related: Signs of life shooting from Saturn’s moon Enceladus could be detectable by spacecraft, scientists say

However, some organic molecules in Enceladus’ plumes, which could be the fingerprints of biological life, can be destroyed by ultraviolet (UV) from the sun. That means there is a desire to reach these molecules while keeping them pristine.

‘We know that Enceladus’ ocean is habitable thanks to Cassini measurements. We know that liquid water, energy and the chemicals carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur exist. These are the ingredients necessary for life as we know it. ‘ said Hendrik. “If we want to know whether ocean-derived biosignatures are present in the plume grains, these grains need to be as pristine as possible and not exposed to UV.”

Hunting for pristine material on Enceladus

To find a spot on Enceladus where such pristine material would be available, Hendrix and the team analyzed data from the Hubble Space Telescope and Cassini spacecraft to see how deeply photons of UV light can penetrate the surface the moon.

“What we find in this study is that there are places on the surface of Enceladus where we could land a spacecraft and take a sample — and we would measure relatively pristine organics,” Hendrix said. “That’s because the sun’s ultraviolet (UV) photons don’t penetrate very deeply into the icy surface.”

The team found that harmful UV photons only penetrate about 100 micrometers into Enceladus’ icy surface, which is only the width of a few human hairs.

“So that upper part of the surface is exposed to those harmful UV photons, but only a percentage of the organics are chemically transformed, and then that material is quickly covered by fresher plume material,” Hendrix explains. “And the deeper grains no longer undergo transformation – because the UV photons cannot interact with the deeper material. The freshly deposited plume grains act as a shield for the underlying material. They act like a sunscreen!”

An illustration shows how UV light affects grains of material on Enceladus' surface, but not deeper material.

An illustration shows how UV light affects grains of material on Enceladus’ surface, but not deeper material.

The results collected by the team are useful because they tell scientists that missions to Enceladus will have an abundance of organics to sample without having to dig too deep.

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– Detecting life on Saturn’s moon Enceladus would require flying past the geyser plume 100 times, study suggests

“Because UV light easily changes organic molecules, the depth at which such light travels to the surface of an ice-covered world really matters. With the short UV penetration depths found, our results ensure that sufficient organic material is trapped and preserved in the ice of Enceladus that can be traced back to the ocean,” said Christopher House, co-author of the study and a scientist at Penn State University, in the statement. “It’s awe-inspiring to think that with known technology we can easily could access a lot of organic material from a habitable alien ocean.”

The team’s research was published in the journal on December 18 Communication Earth & Environment.

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