According to new studies by planetologists from the University of Washington, in the subterranean ocean of Saturn’s satellite Enceladus contains very high concentrations of carbon dioxide and hydrogen, as well as pH levels close to that of Earth, which could well provide life-friendly conditions. The existence of such high concentrations could provide fuel – a kind of chemical “free lunch” – for living organisms.
This was announced by the main investigator Lucas Fafer. Or it may mean that there is no one around who feeds on this fuel. New information on the composition of the ocean Enceladus gives planetary scientists a better idea of the ability of this ocean to preserve life, says Faifer.
What do Enceladus bacteria eat?
Enceladus is a small moon, the ocean world is about 500 kilometers across. Its salty underground ocean is of interest because of its similarity in pH, salinity and temperature to the oceans of the Earth. The plumes of water vapor and ice particles, discovered and studied by the Cassini spacecraft, breaking out hundreds of kilometers into space from the ocean through cracks in the ice-covered surface, tease scientists by inviting them to explore what could contain the ocean below the surface.
But Faifer and his colleagues argue that these plumes do not chemically coincide with the ocean, from which they erupt at a speed of 1,400 kilometers per hour; the eruption process itself changes its composition. Scientists will present their work on June 24 at the AbsciCon2019 astrobiological conference in Bellevue.
Fyfer says that the plumes provide an “imperfect window” to the composition of the subsurface ocean of Enceladus and that the composition of the plume and the ocean can vary greatly. This is due to the fractionation of the plume, that is, the separation of gases, in which some components of the plume break through, while others remain behind.
With this in mind, the scientists returned to the Cassini mission data and created a computer model that takes into account the effects of fractionation in order to get a clearer picture of the composition of the internal ocean of Enceladus. Previous interpretations, as they found out, underestimated the presence of hydrogen, methane, and carbon dioxide in the ocean.
“It is better to find a high concentration of gas than nothing at all,” says Faifer. “It seems unlikely that life could evolve and consume all these free gases if they were not abundant in the ocean.”
Such high levels of carbon dioxide also imply a lower, earth-like level of acidity in the ocean of Enceladus. It is also good for life.
“Although there are exceptions, most of life on Earth lives best in water or consumes water with an almost neutral pH, so such conditions on Enceladus can be encouraging,” he says. “And they greatly facilitate the comparison of this strange ocean world with a more familiar environment.”
Also on Enceladus there may be high concentrations of ammonia, which can be a potential fuel for life. And although high concentrations of gases may indicate a shortage of living organisms that will consume all of this, this does not mean that Enceladus is deprived of life. Maybe microbes are simply not enough to consume all the available chemical energy.
Scientists can use gas concentrations to determine the upper limit of certain types of possible life that may exist in the ice-cold ocean of Enceladus. In other words, “considering that there is so much free food available, what is the maximum amount that her life can eat to leave behind the amount we see?”.
“Future missions of spacecraft will taste plumes for signs of life.”