by New research suggests that there are places on the surface of Saturn’s moon Enceladus where spacecraft could land to find amazing traces of the key ingredients of life. These biosignals are believed to come from subsurface oceans within the earth’s icy shell.
Enceladus Subsurface oceans have long been known to contain organic molecules – compounds made up of carbon, oxygen and nitrogen. Before he plunged to the surface of it Saturn in 2017, the Cassini spacecraft flew through plumes of material erupting through fissures in the surface of Enceladus, finding organic molecules such as methane and ethane as well as other complex compounds that reached enormous heights.
About 90% of the larger grains in this material, sent thousands of miles beyond Enceladus, are escapes from the Saturnian system. Instead, they fall back to the surface of the Saturnian moon, scientists say now, where they can theoretically be collected and examined by spacecraft.
“We can learn a lot about potential biomarkers in the ocean of Enceladus by sending a mission to the surface of Enceladus. Previously, it was thought that in order to taste the freshest material from the ocean of Enceladus, you have to fly through the dust and measure pure- grains and gases,” Amanda R. Hendrix, senior scientist at the Planetary Science Institute and research leader, said in a statement. “But we now know that you can land on the surface and be confident that your organic instruments can measure a relatively pristine plume – obtained from the ocean.”
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Some organic molecules in Enceladus plumes that could be fingerprints for biological life, however, may have been destroyed by ultraviolet (UV) from the sun. That means there is a desire to get to these molecules as long as they remain undamaged.
“We know that the ocean of Enceladus is habitable thanks to the measurements of Cassini. We know that there is liquid water, energy, and the chemicals carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. These are the ingredients necessary for the life as we know it,” said Hendrix. “If we want to know if any ocean-derived biomarkers are present in the plume grains, we need these grains to be as pristine and unexposed to UV as possible.”
Hunt for pristine material on Enceladus
To find a place on Enceladus where such excellent material would be available, Hendrix and the team analyzed data from Hubble Space Telescope and the Cassini spacecraft to see how photons of deep UV light can penetrate a 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 want to be measuring relatively pristine organisms,” Hendrix said. “That’s because the sun’s ultraviolet (UV) photons don’t penetrate deep into the icy surface.”
The team found that harmful UV photons only penetrate about 100 micrometers into the icy surface of Enceladus, which is only the width of a few human hairs.
“So that the highest part of the surface is exposed to those damaging UV photons, but only a percentage of the organic is chemically transformed, and then pretty soon that material is covered with fresher plume material,” explained Hendrix. “And the deeper grains are not transformed any more – because the UV photons are prevented from interacting with the deeper material. The recently deposited fine grains act as a shield for the original material. They act as sunscreen!”
The results the team collects are useful because they tell scientists that missions to Enceladus will have an abundance of organisms to sample without having to plow too deep.
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“Because UV light easily transforms organic molecules, the depth that such light travels into an ice-covered Earth is of great importance. With the short UV penetration depth found, our results ensure that “There is a lot of organic matter locked up and preserved in Enceladus’ ice that can be traced back to its ocean,” said Christopher House, co-author of the study and a scientist at Penn State University, in the statement. “It’s surprising to think that with the technology we know, we can easily find a lot of organic material from an extraterrestrial ocean that is habitable.”
The team’s research was published on 18 December in the journal Communication The World and the Environment.
