A new study suggests Enceladus’s oceans have a high amount of carbon dioxide and hydrogen. That could provide conditions favorable to life.

New research from planetary scientists at the University of Washington suggests Enceladus’s oceans probably have higher than previously thought concentrations of carbon dioxide and hydrogen and a more Earthlike pH level. So, the abundance of these gases is possibly providing fuel for living microbes — if there are any.

“The presence of such high concentrations could provide fuel — a sort of chemical “free lunch” — for living microbes. Alternatively, it could mean “that there is hardly anyone around to eat it,” lead researcher Lucas Fifer, a UW doctoral student in Earth and space sciences said.

“The new information about the composition of Enceladus’ ocean gives planetary scientists a better understanding of the ocean world’s capacity to host life.”

Enceladus, the sixth largest moon of Saturn, is covered in ice. It is 25 times smaller than Earth and about ten times as far from the sun.

But the moon’s salty subsurface ocean has caught the attention of astronomers around the world. That’s because of the similarity in pH, salinity, and temperature to Earth’s oceans.

Water Plumes Have Different Chemicals From Enceladus’s Oceans

NASA’s Cassini spacecraft began studying Enceladus in February 2005 when it passed within 725 miles (1,167 kilometers) of the moon. Cassini found plumes of water vapor and ice particles erupting into space from the ocean through cracks in Enceladus’s surface. Plumes were erupting at 800 miles an hour. So, that gave scientists a glimpse into what the moon’s subsurface ocean might contain.

But the researchers found that the plumes are not chemically the same as the ocean from where they emerged. The eruption process itself changes their composition.

Researchers noted, “The plumes provide an “imperfect window” to the composition of Enceladus’s global subsurface ocean and that the plume composition and ocean composition could be much different. That, they find, is due to plume fractionation, or the separation of gases, which preferentially allows some components of the plume to erupt while others are left behind.”

Fifer and his colleagues are working with ESS faculty members David Catling and Jonathan Toner. They will present their work on June 24 at the astrobiology conference AbSciCon2019 in Bellevue.

However, researchers returned to Cassini data to get a clearer idea of the composition of Enceladus’s inner ocean’s. They found “significant differences” between Enceladus’s plume and ocean chemistry.

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“It’s better to find high gas concentrations than none at all. It seems unlikely that life would evolve to consume this chemical-free lunch if the gases were not abundant in the ocean,” Fifer said.

“Those high levels of carbon dioxide also imply a lower and more Earthlike pH level in the ocean of Enceladus than previous studies have shown. This bodes well for a possible life, too.”

“Although there are exceptions, most life on Earth functions best living in or consuming water with near-neutral pH, so similar conditions on Enceladus could be encouraging. Moreover, they make it much easier to compare this strange ocean world to a more familiar environment.”

“There could be high concentrations of ammonium as well, which is also a potential fuel for life. Also, though the high concentrations of gases might indicate a lack of living organisms to consume it all that does not necessarily mean Enceladus is devoid of life. It might mean microbes aren’t abundant enough to consume all the available chemical energy.”

In other words, he said: “Given that there’s so much free lunch available, what’s the greatest amount that life could be eating to still leave behind the amount we see? How much life would that support?”

“Thanks to Cassini, we know about Enceladus’ ocean and the types of gases, salts, and organic compounds that are present there. Studying how the plume composition changes can teach us yet more about this ocean and everything in it.”

“Future spacecraft missions will sample the plumes looking for signs of life, many of which will be affected just by the eruption process. So, understanding the difference between the ocean and the plume now will be a huge help down the road.”

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