Home South pole ice The ocean of Enceladus is not too salty for life

The ocean of Enceladus is not too salty for life

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Artist’s impression of Enceladus, Saturn’s oceanic moon. Plumes of water vapor shoot up from the South Pole. A new study suggests that Enceladus’ ocean is salty like Earth’s oceans, but not too salty for life. Image via Science Photo Library/Alamy/New Scientist.

Could there be life on Enceladus? This small Saturn moon – like Jupiter’s moon Europa – has a global ocean of water beneath its icy surface. Indeed, previous data from NASA’s Cassini mission has shown that this ocean may well be able to support some forms of life. It has heat, mineral nutrients and organic matter. On July 20, 2022, researchers from the Massachusetts Institute of Technology (MIT) published a new study which suggests that the underground ocean is slightly less salty than Earth’s oceans. Coupled with previous findings, this reinforces the possibility that the ocean of Enceladus harbors living organisms.

Wanying Kang led the research team at MIT. The researchers were able to estimate salinity by studying how the surface ice covers the ocean below. They published their peer-reviewed findings in Scientists progress July 20, 2022.

Karmela Padavic-Callaghan wrote about the tantalizing results in new scientist July 20, 2022.

The salinity of the ocean of Enceladus

On Enceladus, ocean salinity, silicate core, and ice shell all have a significant impact on ocean dynamics and habitability. As the paper writes:

Of deep astrobiological interest, Enceladus appears to have an overall saline subterranean ocean, indicating a current or past water-rock reaction, an important mechanism in the moon’s potential habitability. Here, we investigate how salinity and the distribution of heat production between the silicate core and the ice shell affect ocean dynamics and associated heat transport, a key factor determining the equilibrium geometry of the ice shell. ice.

In particular, the researchers wanted to know how the thickness of the ice shell was related to the salinity of the ocean. Saltier underground oceans should, as a general rule, have thicker ice at the poles of a planet or moon. Less salty oceans would have thinner ice. The study showed that the salinity level on Enceladus is probably intermediate. As the new scientist article explained:

The team designed a theoretical model detailing how ocean salinity, ocean currents and ice geometry influence each other on a planet or moon, then modified it to best replicate the properties of ice on Earth. Enceladus.

Paper:

Of the scenarios explored here, the pronounced variations in ice thickness observed on Enceladus are most consistent with warming that is predominant in the ice shell and mid-range salinity.

Salinity is not the only factor

Salinity, however, is not the only habitability factor. As the new scientist quoted article:

David Stevens of the University of East Anglia, UK, says the behavior of ice and water on other planets is directly related to their habitability. At the same time, salinity is only one factor among many, he says.

Sectional view of the ocean under the ice, with a ringed planet in the background.
Sectional view of the underground ocean of Enceladus. The salinity of the ocean seems conducive to life. There is also evidence of hydrothermal vents at the bottom of the ocean, just like on Earth. Image via NASA/ JPL-Caltech/ SwRI.
Sunny edge of barren moon with sprays rising and spreading in black space.
The geysers of Enceladus, Saturn’s moon, seen by Cassini. These huge plumes of water vapor burst through fissures in Enceladus’ South Pole. The Cassini spacecraft analyzed the plumes, finding water vapor, ice particles, salts, methane and a variety of complex organic molecules. Scientists believe the plumes originate from a global ocean below the moon’s icy surface. Image via NASA/ JPL/ Space Science Institute.

Thinner ice on the poles of Enceladus

Interestingly, the study results indicate that the ice above Enceladus’ poles is thinner than at its equator. This would indicate a less salty ocean. Specifically, the specific variation in ice thickness suggests that ocean salinity could be as high as 30 grams of salt in one kilogram of water. It’s salty, but less than the Earth’s oceans, which contain 35 grams of salt per kilogram of water.

All in all, it looks promising for life potential. The waters are salty, like the oceans on Earth, but not too dirty. On the contrary, the ocean of Enceladus is perhaps a little more benign than the oceans of our planet.

Smiling woman head with glasses and parted hair.
Wanying Kang of the Massachusetts Institute of Technology (MIT) conducted the study to determine how salty the ocean of Enceladus is. Image via MIT.
Planet-like sphere with bluish cracks and craters on its surface.
View of Enceladus, Saturn’s moon, via the Cassini spacecraft. Image via NASA/ ESA/ JPL/ SSI/ Cassini Imaging Team/ Carnegie Science.

The heat of the ocean seabed of Enceladus

Another intriguing discovery appears to back up earlier data from the Cassini mission. The team found evidence of heat emanating from the ocean floor on Enceladus. Previous analysis by Cassini of water vapor and organic matter in Enceladus’ famous plumes suggested the existence of hydrothermal vents at the bottom of the ocean. This new evidence would appear to agree with this, although further study is needed.

On Earth, such hydrothermal vents create an oasis for many different types of organisms. They provide essential heat and nutrients to the otherwise dark and hostile depths of the oceans.

Last year, scientists also reported evidence in Cassini data of a large amount of methane in the ocean of Enceladus. Could this be an indication of methanogenic organisms in the ocean?

Conclusion: A new study shows that the underground ocean on Saturn’s moon Enceladus is less salty than the oceans on Earth. This increases the chances that the ocean of Enceladus supports a form of life.

Source: How does salinity shape ocean circulation and ice geometry on Enceladus and other icy satellites?

Via a new scientist