According to a new study, Enceladus, Saturn’s moon, has “defeated” ocean currents buried under 12 miles of ice..
It is already known that Enceladus – one of Saturn’s 82 months – hides water beneath its shiny, frozen surface.
But experts at the California Institute of Technology (Caltech) believe that ocean currents flow on Enceladus a bit like those near Antarctica, led by salt water.
They based their estimates on computer modeling that used data collected by NASA’s Cassini spacecraft, which is no longer operational.
Enceladus is one of the few locations in the solar system with liquid water, along with the Earth and the moon of Jupiter Europe, making it a target of interest to astrobiologists.
The new research could tell scientists where to look for signs of life on Enceladus one day during future satellite missions, according to Caltech.
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Enceladus (pictured 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 by a glistening layer of clean ice, making it one of the most reflective bodies in the solar system.
“Understanding the underground ocean regions may be the most hospitable for life, because we know that one day it could inform the search for signs of life,” said study author Andrew Thompson, a professor of environmental science 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 a quarter the diameter of the Earth’s moon).
Enceladus is covered in a glistening layer of clean ice, making it one of the most reflective bodies in the solar system.
Despite its relatively small size, Enceladus attracted the attention of scientists in 2014 thanks to data from Cassini.
At that time, the spacecraft discovered evidence of its large underground ocean and took water from geyser-like eruptions that appear through ice cracks at its southern pole.
Water jets and some solid particles, such as ice crystals, spill out of fractures on the frozen surface called “tiger stripes”.
Despite the fact that the Earth and Enceladus are home to water, the ocean on Enceladus is almost completely different from that of Earth.
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 due to the sun’s rays and colder in the depths near the bottom of the sea and has wind-affected currents.
Meanwhile, Enceladus appears to have a completely underground ocean, with a depth of at least 30 km, which runs until the end of the month.
Illustration of the interior of Saturn’s moon, Enceladus, showing an ocean of global liquid water between its rocky core and the frozen crust. The thickness of the layers shown here is not to scale
The Enceladus Ocean is cooled at the top by the ice crust and warmed at the bottom by the midday heat.
Despite their differences, the oceans Enceladus and Earth share an important feature – they are salty.
Variations in salinity could serve as the engine of ocean circulation on the Enceladus, as in the Southern Ocean of the Earth, which surrounds Antarctica.
Cassini’s gravitational measurements and heat calculations have already revealed that Enceladus’ ice sheet is thinner at the poles than at the equator.
Surprisingly, the thin ice regions at the poles are likely to be associated with melting, while the thick ice regions at the equator are associated with freezing, Thompson said.
But this affects the ocean currents, because when the salt water freezes, it releases the salts and makes the surrounding water heavier, causing it to sink.
The complete opposite occurs in the thin ice regions at the poles associated with melting.
Cassini is described 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 regions of freezing and melting, identified by the structure of ice, would be connected by ocean currents.
This would create a circulation from the pole to the equator, almost like a conveyor belt, which influences the distribution of heat and nutrients.
The theory provokes the current thinking that Enceladus’ global ocean is homogeneous, apart from a vertical mixture driven by the heat of its core.
“Knowing the distribution of ice allows us to place constraints on traffic patterns,” said Ana Lobo, a Caltech graduate student.
“An idealized 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 the pole to the equator that influences the distribution of heat and nutrients.”
Scientists are still reaping the rewards of the rich data obtained by the Cassini robotic spacecraft, which has been active for almost 20 years since its launch in October 1997.
Cassini’s mission ended in September 2017, when it was deliberately flown 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 have been confirmed around the planet’s orbit in 2019, making it the “king of the moon” of the solar system, exceeding the total number of 79 Jupiter.
The new study was published in Nature Geoscience.
WHAT DID CASSINI DISCOVER DURING THE 20-YEAR MISSION?
Cassini launched from Cape Canaveral, Florida, in 1997, 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.
During that time, he discovered another six months around Saturn, three-dimensional structures that rise above Saturn’s rings and a huge storm that erupted on the planet for almost a year.
On December 13, 2004, he made his first flyby of the months of Saturn, Titan and Dione.
On December 24, it launched the Huygens spacecraft built by the European Space Agency on the moon of Saturn Titan to study its atmosphere and surface composition.
There he discovered strange lakes of hydrocarbons made of ethane and methane.
In 2008, Cassini completed its main mission to explore the Saturn system and began expanding its mission (the Cassini Equinox Mission).
In 2010 began the second mission (Cassini Solstice Mission), which lasted until it exploded in the atmosphere of Saturn.
In December 2011, Cassini obtained the highest resolution images of Saturn’s moon, Enceladus.
In December of the following year, it 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 the moon of Saturn, Rhea and measured its internal structure and gravitational attraction.
Cassini not only studied Saturn – he also captured incredible views of its many months. In the image above, Saturn’s moon, Enceladus, can be seen drifting in front of the rings and the tiny Pandora’s moon. She was caught on November 1, 2009, the whole scene being illuminated by the Sun.
In July of that year, Cassini captured a black-lit Saturn to examine the rings in detail and also captured an image of the Earth.
In April of this year, it completed its closest flight to Titan and began its orbit in the Grande Finale, which ended on September 15.
“The mission has changed the way we think about where life could have developed beyond our Earth,” said Andrew Coates, head of the Planetary Science Group at Mullard Space Science Laboratory at University College London.
“Like Mars, the outer moons of the planet, such as Enceladus, Europe and even Titan, are now supporters of life elsewhere,” he added. “I completely rewrote the textbooks on Saturn.”