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EI2GYB > ASTRO 05.10.25 14:04l 44 Lines 5599 Bytes #57 (0) @ WW
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Subj: New Organic Molecules Found In Old Cassini Data
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New Organic Molecules Found In Old Cassini Data
Enceladus' ice continues to get more and more intriguing as researchers continue to unlock more secrets taken from a probe over ten years ago. When Cassini crashed into Saturn in 2017, it ended a 13 year sojourn that is still producing new research papers today. A recent one in Nature Astronomy from the researchers at the Freie Universität Berlin and the University of Stuttgart found hints of organic molecules discovered for the first time on the icy moon, some of which could serve as precursors to even more advanced biomolecules.
To understand how these organic molecules lay hidden in the data for almost a decade, its best to first look at how they were captured by Cassini in the first place. Cassini did 23 flybys of Enceladus during its mission. Most of those were done at a speed of around 12 km/s. However, the fastest, known as E5, was done at around 17.7 km/s - almost 50% faster. Also, that flyby captured "younger" ice grain samples that had only been ejected from the moon a few minutes before, whereas most of the other data was based on ice grains that were either days or decades old - it was hard for the researchers to tell.
That data was collected by the Cosmic Dust Analyzer (CDA), a mass spectrometer that was designed to determine the chemical composition of the dust and ice in the Saturnian system. It used a technique called impact ionization, where dust or ice particles could hit a rhodium target in the instrument. They would be immediately vaporized, and the CDA would analyze their Time of Flight spectrum to determine what types of ions were there. Scientists could then trace back the ion species to the molecule trapped in the dust and ice that created them.
At slower speeds, like those of most of the Enceladus passes, water-cluster ions could be introduced into the mass spec, masking other organic molecules. At the faster speed of E5, they didn't, making the signal for the organics that were released as part of the collision much clearer. To prove the faster speeds create different signals, the authors compared some of the data with results from electron ionization mass spectrometry data collected back on Earth. With that in mind, the researchers did confirm the presence of organics that had previously been found in the E ring around Saturn, such as "aromatics" that the common building blocks of organic molecules.
But more interestingly, they also found evidence for some of those more advanced organic molecules. It was hard to differentiate exactly what compounds were in the mix, but the paper describes them as esters and/or alkenes as well as ethers and/or ethyls. These more advanced organic molecules are important in the overarching search for life on the icy moon as they prove that the hydrothermal vents that are likely the source are capable of producing more complex molecules than originally thought.
That's great for astrobiologists and missions planners alike - it raises the possibility that even more complex organic chemistry are going on near those hydrothermal vents. Their Earth analogues are famous for hosting entire ecosystems that rely strictly on chemical energy, rather than solar, for their existence. Some theorists even believe that life on Earth might have started around them.
One potential mission to Enceladus to explore it further is the Enceladus Vent Explorer, which Fraser discusses with Dr. Hiro Ono
Since this new paper lends credence to the idea that the hydrothermal vents on Enceladus can create even more complex biomolecules, its not too far of a stretch to argue that they could also make the next step to creating lipids and amino acids, some of the fundamental building blocks of life. Unfortunately, its unclear when we will send another probe back to Enceladus to look at it in more detail. However, there is a planned mission to visit Europa (Europa Clipper), another icy moon with potential hydrothermal vents, that will use a similar instrument to the CDA called the SUrface Dust Analyzer (SUDA). So in 2040 or so, we might get some more data to prove whether Enceladus is the only moon to have such organic molecule creation engines.
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