A new theory proposed by planetary scientists from Caltech and NASA’s jet lab calls into question the current idea that the marine global ocean Enceladus, the sixth largest Saturn, is homogeneous.
In 2014, NASA’s Cassini spacecraft discovered evidence of a large underground ocean on Enceladus and took water samples from geyser-like eruptions that occur through ice cracks at the South Pole.
It is one of the few places in the solar system with running water, which is why it is a target of interest to astrobiologists looking for signs of life.
The ocean on Enceladus is almost completely indistinguishable from Earth’s.
The Earth’s ocean is relatively shallow, covers three-quarters of the planet’s surface, is warmer at the top than the sun’s rays, and cooler at depth near the sea floor, and has currents affected by the wind.
Meanwhile, Enceladus appears to have an ocean that stretches around the world and is completely subterranean, at least 30 km deep, cooled at the top near an ice shell, and heated at the bottom by heat from the moon’s core.
Despite their differences, Caltech student Ana Lobo and colleagues suggest that Enceladus ’ocean has currents similar to those on Earth.
The oceans of Enceladus and Earth share one important characteristic: they are salty. And as the team has shown, variations in salinity could serve as drivers of ocean circulation on Enceladus, just as they do in the Earth’s southern ocean.
“Gravitational measurements and heat calculations from Cassini have already revealed that the ice shell is thinner at the poles than at the equator,” said Professor Andrew Thompson, a researcher in the Department of Geological and Planetary Sciences at Caltech.
“Thin ice regions at the poles are probably related to melting, and dense ice regions at the equator by freezing.”
This affects ocean currents, because when salt water freezes, it releases salt and makes the surrounding water difficult, causing it to sink. The opposite happens in the regions of the melt.
“Knowing the distribution of ice allows us to limit the patterns of circulation,” Lobo said.
The team’s computer model suggests that the freezing and melting areas, identified by the structure of the ice, would be connected by ocean currents.
This would create a circulation from the pole to the equator that affects the distribution of heat and nutrients.
“Understanding which parts of the subterranean ocean might be the most hospitable to life, because we know that one day they could be used for efforts in search of signs of life,” Professor Thompson said.
The study was published in the journal Nature Geoscience.
AH Lobo and others. The ocean from the pole to the equator overturns the circulation on Enceladus. Nat. Geosci, published online March 25, 2021; doi: 10.1038 / s41561-021-00706-3