Saturn’s moon Enceladus has ‘choppy’ ocean currents under its 12 miles of ice, experts say


Saturn’s moon Enceladus has ‘choppy’ ocean currents buried under its 12 miles of ice, new study finds.

It is already known that Enceladus, one of the 82 moons of Saturn, hides water under its shiny, icy surface.

But experts at the California Institute of Technology (Caltech) believe that ocean currents flow on Enceladus a bit like those near Antarctica, driven by salt water.

They have based their estimates on computer models that used data collected by NASA’s Cassini spacecraft, which is no longer operational.

Enceladus is one of the few places in the Solar System with liquid water, along with Earth and Jupiter’s moon Europa, making it a target of interest to astrobiologists.

The new research could inform scientists where to one day look for signs of life on Enceladus during future satellite missions, according to Caltech.

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Enceladus (in NASA’s Cassini satellite image) is the sixth largest of Saturn’s moons, with a diameter of about 310 miles. The moon is covered in a glistening layer of clean ice, making it one of the most reflective bodies in the Solar System.

ENCELADUS: BRIEF FACTS

Discovered: August 28, 1789

Guy: Ice Moon

Diameter: 313 miles (504 km)

Orbital period: 32.9 hours

Duration of the day: 32.9 hours

Dough: About 680 times less than Earth’s moon

Source: NASA.

“ Understanding which regions of the underground ocean might be the most hospitable to life as we know it could one day inform efforts to look for signs of life, ” said study author Andrew Thompson, professor of environmental science and engineering at Caltech. .

Enceladus, Saturn’s sixth largest moon of its 82 total, is a frozen sphere just 313 miles in diameter (about one-seventh the diameter of Earth’s moon).

Enceladus is covered in a bright 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 brave spacecraft discovered evidence of its vast underground ocean and sampled water from geyser-like eruptions that occur through fissures in the ice at its south pole.

Jets of water and some solid particles, such as ice crystals, erupt from fractures in the frozen surface called ‘tiger stripes’.

Despite Earth and Enceladus harboring water, the ocean on Enceladus is almost completely different from Earth’s.

Earth’s ocean is relatively shallow, averaging 2.2 miles (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 cooler in the depths near the seafloor, and it has currents that are affected by the wind.

Meanwhile, Enceladus appears to have a completely underground ocean at least 18.6 miles (30 km) deep, circling the moon.

Enceladus' outer shell
An illustration showing liquid water between the rocky core of the moon and the icy crust

Illustration of the interior of Saturn’s moon Enceladus, showing a global liquid water ocean between its rocky core and icy crust. The thickness of the layers shown here is not to scale.

Enceladus’ ocean is cooled at the top near the ice sheet and warmed at the bottom by heat from the moon’s core.

Despite their differences, the oceans of Enceladus and Earth share one important characteristic: they are salty.

Variations in salinity could serve as drivers of ocean circulation on Enceladus, just as they do in Earth’s Southern Ocean, which surrounds Antarctica.

Gravitational measurements and Cassini heat calculations had already revealed that Enceladus’ ice sheet is thinner at the poles than at the equator.

Unsurprisingly, thin ice regions at the poles are likely associated with melting, while thick ice regions at the equator are associated with freezing, Thompson said.

But this affects ocean currents, because when salty water freezes, it releases the salts and makes the surrounding water heavier, causing it to sink.

Quite the opposite occurs in the thin ice regions at the poles associated with melting.

Cassini is depicted here in an illustration from NASA.  Cassini was launched from Cape Canaveral, Florida in October 1997

Cassini is depicted here in an illustration from NASA. Cassini was launched from Cape Canaveral, Florida in October 1997

A computer model, based on Thompson’s studies of Antarctica, suggests that the regions of freezing and melting, identified by the structure of the ice, would be connected by ocean currents.

This would create a pole-to-equator circulation, almost like a conveyor belt, influencing the distribution of heat and nutrients.

The theory challenges current thinking that Enceladus’ global ocean is homogeneous, apart from vertical mixing driven by the warmth of its core.

“Knowing the distribution of the ice allows us to establish restrictions on the circulation patterns,” said Caltech graduate student Ana Lobo.

‘An idealized computer model, based on Thompson’s studies of Antarctica, suggests that regions of freezing and melting, identified by the structure of the ice, would be connected by ocean currents.

“This would create a pole-to-equator circulation that influences the distribution of heat and nutrients.”

Scientists are still reaping the rewards from the rich data obtained by the robotic Cassini 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 running out of fuel.

In 2019, Cassini data revealed that a lake on Saturn’s largest moon Titan is rich in methane and 300 feet deep.

Another 20 new moons were confirmed in orbit around the planet in 2019, making it the ‘lunar 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 SATURNO?

Cassini was launched from Cape Canaveral, Florida in 1997, then spent seven years in transit followed by 13 years in orbit around Saturn.

An artist's impression of the Cassini spacecraft studying Saturn

An artist’s impression of the Cassini spacecraft studying Saturn

In 2000, he spent six months studying Jupiter before reaching Saturn in 2004.

In that time, he discovered six more moons around Saturn, three-dimensional structures towering above Saturn’s rings, and a giant storm that hit the planet for nearly a year.

On December 13, 2004, it made its first flyby of Saturn’s moons Titan and Dione.

On December 24, it launched the Huygens probe built by the European Space Agency on Saturn’s moon Titan to study its atmosphere and the composition of its surface.

There he discovered mysterious hydrocarbon lakes made of ethane and methane.

In 2008, Cassini completed its primary mission to explore the Saturn system and began its mission extension (the Cassini Equinox Mission).

In 2010 it began its second mission (Cassini Solstice Mission) that lasted until it exploded in 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 Rhea and measured its internal structure and gravitational pull.

Cassini not only studied Saturn, it also captured incredible views of its many moons.  In the image above, Saturn's moon Enceladus can be seen drifting before the rings and the small moon Pandora.  It was captured on November 1, 2009, with the entire scene illuminated by the sun.

Cassini not only studied Saturn, it also captured incredible views of its many moons. In the image above, Saturn’s moon Enceladus can be seen drifting before the rings and the small moon Pandora. It 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 Earth.

In April of this year, it completed its closest flyby of Titan and began its Grande Finale orbit that ended on September 15.

“The mission has changed the way we think about where life may have developed beyond our Earth,” said Andrew Coates, director of the Planetary Sciences Group at the Mullard Space Sciences Laboratory at University College London.

“Besides Mars, the moons of the outer planets like Enceladus, Europa and even Titan are now the main contenders for life elsewhere,” he added. “We have completely rewritten the textbooks on Saturn.”

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