According to a new study, Enceladus, on Saturn’s moon, has “underground” ocean currents buried beneath its 12 miles of ice..
Enceladus, one of Saturn’s 82 moons, is already known to hide water beneath its shiny, icy surface.
But experts at the California Institute of Technology (Caltech) think ocean currents flowing into Enceladus a bit like those near Antarctica, propelled by salt water.
They have based their estimates on computer modeling that used data collected by NASA’s Cassini spacecraft, which no longer works.
Enceladus is one of the few locations in the solar system with liquid water, along with Jupiter’s Earth and Moon Europe, making it a target of interest to astrobiologists.
The new research could tell scientists where to look for signs of life on Enceladus during future satellite missions, according to Caltech.
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Enceladus (pictured by NASA’s Cassini satellite) is the sixth largest place on Saturn’s moons, with a diameter of about 310 kilometers. The moon is covered by a bright layer of clean ice, making it one of the most reflective bodies in the solar system.
“Understand which regions of the subterranean ocean may be the most hospitable for life, as we know that one day we could report efforts to look for signs of life,” said study author Andrew Thompson, a professor of environmental sciences and engineering at Caltech.
Enceladus, Saturn’s sixth largest moon out of 82 in total, is a frozen sphere only 313 miles in diameter (about one-seventh the diameter of the Earth’s moon).
Enceladus is covered by a shiny layer of clean ice, making it one of the most reflective bodies in the solar system.
Despite its relatively small size, Enceladus caught the attention of scientists in 2014 thanks to Cassini data.
At that time, the solid spacecraft discovered evidence of its large underground ocean and took water samples from geyser-like eruptions that occur through ice cracks in its south pole.
Water jets and some solid particles, such as ice crystal, spring from fractures on the frozen surface called “tiger stripes.”
Despite the fact that Earth and Enceladus carry water, Enceladus’ ocean is almost completely different from Earth’s.
Earth’s ocean is relatively shallow, averaging 3.6 km, and covers three-quarters of the planet’s surface.
Our ocean is also warmer at the top thanks to the sun’s rays and colder at depths near the bottom of the sea and has wind-affected currents.
Meanwhile, Enceladus appears to have a completely underground ocean at a minimum depth of 30 km (18.6 miles) that runs across the moon.
Illustration of the interior of Saturn’s moon, Enceladus, showing an ocean of global liquid water between its rocky core and the icy crust. The thickness of the layers shown here is not to scale
The Enceladus Ocean cools at the top near the ice shell and heats at the bottom by the heat of the moon’s core.
Despite their differences, the oceans of Enceladus and Earth share an important feature: they are salty.
Variations in salinity could serve as engines of ocean circulation in Enceladus, just as they do in the southern ocean of the Earth, which surrounds Antarctica.
Cassini’s gravitational measurements and heat calculations had already revealed that the Enceladus ice sheet is thinner at the poles than at the equator.
Not surprisingly, thin ice regions at the poles are probably associated with melting, while thick ice regions at the equator are associated with freezing, Thompson said.
But this affects ocean currents, as when salt water freezes, it releases salts and makes the surrounding water heavier and cause it to sink.
The opposite happens in thin ice regions at the poles associated with melting.
Cassini is depicted here in a NASA illustration. Cassini was launched from Cape Canaveral, Florida, in October 1997
A computer model, based on Thompson’s studies of Antarctica, suggests that the freezing and melting regions, identified by the structure of ice, would be connected by ocean currents.
This would create a circulation from pole to equator, almost like a conveyor belt, which influences the distribution of heat and nutrients.
The theory challenges the current thinking that the global ocean of Enceladus is homogeneous apart from some vertical mixture driven by the heat of its core.
“Knowing the distribution of ice allows us to put restrictions on traffic patterns,” said Ana Lobo, a Caltech graduate student.
An idealized computer model, based on Thompson’s Antarctic studies, suggests that the freezing and melting regions, identified by the structure of the ice, would be connected by ocean currents.
“This would create a circulation from pole to equator that influences the distribution of heat and nutrients.”
Scientists are still reaping the benefits of rich data from the Cassini robotic spacecraft, which was active for nearly 20 years after its launch in October 1997.
Cassini’s mission ended in September 2017, when it was deliberately blown into Saturn’s upper atmosphere before it ran out of fuel.
In 2019, Cassini data revealed that a lake on Saturn’s largest moon, Titan, is rich in methane and 300 meters deep.
Another 20 new moons orbiting the planet in 2019 were confirmed, making it the “moon king” of the solar system, surpassing Jupiter’s total of 79.
The new study has been published in Nature Geoscience.
WHAT DID CASSINI DISCOVER DURING HIS 20-YEAR MISSION TO SATURN?
Cassini launched from Cape Canaveral, Florida in 1997, and then spent seven years in transit followed by 13 years orbiting Saturn.
An artist’s impression of the Cassini spacecraft studying Saturn
In 2000 he spent six months studying Jupiter before reaching Saturn in 2004.
At that time, he discovered six more moons around Saturn, three-dimensional structures rising above Saturn’s rings, and a giant storm that lasted nearly a year on the planet.
On December 13, 2004 he made his first flyby of the moons of Saturn, Titan and Dione.
On December 24, he released the Huygens spacecraft built by the European Space Agency on Saturn’s moon Titan to study its atmosphere and surface composition.
There he discovered disturbing hydrocarbon lakes made of ethane and methane.
In 2008, Cassini completed its main mission of exploring Saturn’s system and began its expansion (the Cassini Equinox Mission).
In 2010 he began his second mission (Cassini’s Solstice Mission) which lasted until it exploded into Saturn’s atmosphere.
In December 2011, Cassini obtained the highest resolution images of Saturn’s moon, Enceladus.
In December of the following year he tracked the transit of Venus to test the feasibility of observing planets outside our solar system.
In March 2013, Cassini made the last flyby of Saturn’s moon, Rea, and measured its internal structure and gravitational attraction.
Cassini not only studied Saturn, but captured incredible views of its many moons. In the image above, Saturn’s moon, Enceladus, can be seen drifting in front of the rings and the small moon Pandora. He was captured on November 1, 2009, with the entire scene illuminated by the Sun.
In July of that year, Cassini captured a black-lit Saturn to examine the rings in great detail and also captured an image of the Earth.
In April this year it completed its closest overflight to Titan and began its Grande Finale orbit, which ended on 15 September.
“The mission has changed the way we think about where life may have developed beyond our Earth,” said Andrew Coates, head of the Planetary Science Group at Mullard Space Science Laboratory at University College London.
“Apart from Mars, the moons of the outer planet like Enceladus, Europe and even Titan are now the main candidates for life elsewhere,” he added. “We have completely rewritten the textbooks on Saturn.”