Saturn鈥檚 moon Enceladus appears to have a greater range of complex organic molecules than previously thought, increasing the likelihood of chemical reactions that produce the building blocks of life.
Enceladus is one of the most promising places for life to exist elsewhere in our solar system. It has a vast liquid ocean underneath its icy crust, from which plumes of ice and vapour erupt, and there is some evidence of energy sources on the seabed, like the hydrothermal vents in Earth鈥檚 oceans.
The spacecraft Cassini, which orbited Saturn and its moons for 13 years before smashing into the planet in 2017, sampled icy rock grains in one of Saturn鈥檚 outer rings, which are thought to come from the plumes. Those samples, studied with the probe鈥檚 Cosmic Dust Analyzer, have previously confirmed that Enceladus has all six of the chemical elements needed for life as we know it: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulphur. Cassini also made a closer flyby of the moon, collecting grains from the plumes themselves, but these have been less closely analysed.
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Now, in a new look at the data Cassini sent back about the plume samples, at the Free University of Berlin and his colleagues have found evidence of a wide range of chemical groups that are common to many biological molecules. They included esters, alkenes and ethers, as well as complex molecules containing nitrogen and oxygen, Khawaja told the Europlanet Science Congress in Berlin on 11 September.
While the researchers can鈥檛 pinpoint exactly which molecules these chemical groups came from, their presence means there are more possible pathways for chemical reactions to produce fats or nucleotide bases, the building blocks of DNA.
One reason why these chemicals were not being detected in Saturn鈥檚 ring is that Cassini detected less water in the ice grains near the plume, so Khawaja and his team could detect the organic chemical signatures more clearly.
鈥淲e knew already from analysis that had been done before that there were heavier molecules, but this is going into more detail about exactly what they might be,鈥� says at University College London.
This helps bolster the idea that Enceladus could host life, says Coates, but it will be very hard to establish exactly what molecules are in these grains, because of the technical limitations of the tools that were on board Cassini. 鈥淚t wasn鈥檛 designed to actually look for life, but more information about building blocks for life is certainly something which will keep us going for some time,鈥� he says.
