The latest data from the deceased Cassini probe pointed to the presence of complex organic molecules on the surface of Enceladus, a potentially habitable moon of Saturn, and in the waters of its subglacial ocean. Scientists write about this in an article in the journal Nature.
“Enceladus surprised us once again. Previously, we were able to find in space only the simplest organics, in which several carbon atoms were present, and even this was considered a miracle. We managed to discover molecules with a mass ten times that of methane. Thus, this moon is still the only planet, besides the Earth, which has everything - water, organic matter, a source of energy - for the birth of life,”says Christopher Glein of the Southwest Research Institute in Boulder (USA).
First cradle
In 2005, Cassini discovered jets of water ice and steam particles on Enceladus, which are ejected into space from parallel cracks near the South Pole - the so-called "tiger stripes". This discovery raised the question of the source of this steam and ice.
In March 2015, 10 years after the discovery of tiger stripes and geysers at Enceladus, the Cassini probe showed that there is a global ocean of liquid and hot water in the bowels of this moon of Saturn. It was "given out" by particles of sand and frozen water droplets thrown into space from the south pole of Enceladus along with the eruptions of geysers.
Two years ago, planetary scientists found a potential source of energy for life on Enceladus - hydrogen molecules in its emissions, as well as alcohol-methanol. Discoveries like these are causing scientists to argue more and more often and fiercely about whether life can exist in its waters and how it should be sought. One of NASA's next "mid-range" probes, the ELSAH project, will be sent to Entslad to seek the answer to this question.
These discussions will be heightened by the discovery that Cassini made during its last rapprochement with Enceladus in December 2015. During this "rendezvous", the probe flew at a distance of about 5 thousand kilometers from the surface of the moon of Saturn and collected a large amount of dust particles and frozen ice crystals ejected by its geysers.
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The chemical composition of these grains of dust and ice was analyzed by two mass spectrometers, CDA and INMS. Both of these devices were made more than twenty years ago, which is why their capabilities were very modest - they could determine the types of atoms and the mass of molecules present in these samples of matter, but not their formulas.
The chemistry of life
This is enough to detect simple molecules such as water (mass - 18), ammonia (17) or methane (16), but not enough to reveal the composition of complex hydrocarbons, proteins and other organics. However, the high mass of compounds and some features of their spectrum can produce more complex substances.
For example, both devices indicated the presence of complex and heavy compounds in the Enceladus emissions, whose weight exceeded 200 atomic mass units. They, as the spectrum of their individual scraps hinted at, were complex organic molecules, some of which belonged to the number of aromatic hydrocarbons, while others were alcohols and amines.
All these molecules are considered today one of the main "building blocks" of life, of which all the components of the cells of living beings are composed. As scientists emphasize, the same molecules can arise in an abiogenic way, but how exactly they could appear in the ocean of Enceladus is not yet clear.
On the other hand, now we can safely say that Enceladus has not only a potential source of "food" for future microbes in the form of hydrogen molecules, but also "building blocks" from which the first extraterrestrial organisms may or have already emerged. This, according to the authors of the article, significantly increases the scientific value of sending a repeat mission to Saturn.
“Our discovery is important not only for us, but also for future generations. New probes must fly through Enceladus's emissions and study these molecules with high-resolution spectrometers, which will help us uncover the story of their birth. In any case, now we can seriously think that these substances may be of biogenic origin,”concludes Glein.