Saturn's moon's subterranean sea Enceladus is likely to have higher than previously known concentrations of carbon dioxide and hydrogen and a more terrestrial pH level, potentially beneficial to life, according to new research by planetary scientists at the University of Washington.
The presence of such high concentrations could provide fuel-a kind of chemical "free lunch" for living microbes, said lead researcher Lucas Fifer a UW graduate student in Soil and Space Sciences. Or it could mean "there is almost no one at home."
The new information on the composition of the Enceladus Sea gives planetary scientists a better understanding of the marine world's ability to host life. Fifer said.
Enceladus is a small moon, a sea world about 310 miles (500 kilometers) across. The salted subterranean ocean is of interest because of the similarity in pH, salinity and temperature to Earth's oceans. Plumes of water vapor and ice particles – spotted and studied by the Cassini spacecraft – eruptions hundreds of miles in space from the sea through cracks in the Enceladu ice cap surface provide an excellent insight into what the moon's subterranean sea can contain.
But Fifer and colleagues found that plumes are not chemically the same as the sea from which they break 800 miles per hour; The actual outbreak process changes their composition. He works with ESS faculty members David Catling and Jonathan Toner. They will present their work on June 24 at the astrobiology conference AbSciCon2019 in Bellevue.
Fifer and colleagues say that the plumes give an "incomplete window" to the composition of the Enceladus global subterranean sea, and that the plum composition and the composition of the sea could be very different. What they find is due to plum fractionation or separation of gases, which preferably allow some parts of the plume to break out while others are left behind.
This in mind returned to data from the Cassini mission with a computer simulation that accounts for the effects of the fractions, to get a clearer idea of the composition of the Enceladus inner sea. They found "significant differences" between Enceladus plume and ocean chemistry. Earlier interpretations found they underestimate the presence of hydrogen, methane and carbon dioxide in the ocean.
"It's better to find high gas concentrations than none at all," Fifer said. "It seems unlikely that life will evolve to consume this chemical free lunch if the gas was not abundant in the ocean."
These high levels of carbon dioxide also imply a lower and more terrestrial pH in the Enceladu sea than previous studies have shown. This sounds good to the possible life, says Fifer.
"Although there are exceptions, most life on earth works best in living or consuming water with almost neutral pH, so similar conditions on Enceladus could be encouraging," he said. "And they make it much easier to compare this strange sea world with a more familiar environment."
There may also be high concentrations of ammonium, which is also a potential fuel for life. And although the high concentrations of gases may indicate lack of living organisms to consume it all, Fifer said, it doesn't necessarily mean that Enceladus is without life. It may mean that microbes are just not abundant enough to consume all the available chemical energy.
The researchers can use the gas concentrations to determine an upper limit for certain types of possible lives that could exist in the icy sea of Enceladus. 19659005] In other words, he said: "Given that so much free lunch is available, what is the biggest amount of money life could eat to still leave the amount we see? How much life will it support?"
Thanks to Cassini, he said we know about Enceladus's sea and the types of gases, salts and organic compounds present there. Studying how the space composition changes can teach us even more about this sea and everything in it.
"Future spacecraft will try the climbers looking for signs of life, many of which will be affected just at the outbreak" Fifer said. "So the understanding of the difference between the sea and the plume will now be a great help down the road."
Scientists find signs of complex organic molecules from Enceladus
Abundance of gases in the Enceladus Sea is a potential fuel – if life is there to consume it (2019, June 20)
June 21, 2019
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