Recent observations using the James Webb Space Telescope suggest that there may be an ocean hidden beneath the surface of Ariel, one of Uranus’ moons.
Using the James Webb Space Telescope, astronomers collected emission spectra from Ariel and compared them with spectra from chemical mixtures simulated in the laboratory. This showed that this moon had rich deposits of carbon dioxide. This is interesting because in the icy regions of the solar system where Uranus orbits – 20 times further from the Sun than Earth – carbon dioxide easily turns to gas and escapes into space. This, in turn, means that some process must bring CO2 to Ariel’s surface.
Until now, the most popular idea was that interaction between the moon’s surface and charged particles in Uranus’ magnetosphere creates carbon dioxide through a process called radiolysis. However, new research has been published in The Astrophysical Journal Letters (DOI: 10.3847/2041-8213/ad566a) indicates that carbon dioxide and other molecules are escaping from the interior of the moon, possibly from the subsurface ocean.
Ariel
Ariel is among the five largest moons of Uranus. 28 natural satellites surround the ice giant. At least that’s what we know. The five largest are named Titania (diameter about 1,578 km), Oberon (diameter about 1,522 km), Umbreel (diameter about 1,169 km), Ariel (diameter about 1,158 km ) and Miranda (diameter about 471 km).
Ariel was discovered along with Umbreel in 1851 by William Lassell. The name was taken from two different literary works – from William Shakespeare’s play “The Tempest” and the poem “The Kidnapped Lock” by Alexander Pope. In 1986, during its flyby of Uranus, the Voyager II probe took pictures of Ariel, which are the only high-resolution pictures of the moon we have to date. These images showed Ariel’s shaking surface and a deep and long gorge.
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Researchers believe that Ariel is made up of ice and rocky materials. The surface is relatively young and shows signs of geological activity, possibly driven by tidal heating. Research published last year concluded that there may be water on the moon.
Uranus in the solar system is characterized by an axis of rotation, which is very tight. Its poles are where most planets have their equator. Ariel orbits Uranus in the equatorial plane, which is almost perpendicular to the planet’s orbit.
Subsurface ocean
Chemical elements and molecules absorb and emit light at specific wavelengths, leaving individual “fingerprints” on their emission spectrum. Using the Webb Telescope, a research team led by Richard Cartwright from the Johns Hopkins Applied Physics Laboratory collected spectra of the moon, which allowed them to determine its chemical composition in detail. By comparing this with simulated spectra from a chemical mixture prepared in a laboratory on Earth, it revealed that Ariel has some of the richest carbon dioxide deposits in the solar system. In addition, scientists found chemical signatures of carbon monoxide in the spectrum.
– It shouldn’t be there. You have to get down to 30 kelvins (minus 233 degrees Celsius – editor’s note) before carbon monoxide becomes stable, Cartwright said. Meanwhile, Ariel’s average surface temperature is about 18 degrees Celsius higher. – Carbon monoxide must be actively replenished, of course – added the researcher.
Cartwright admitted that radiolysis could account for some of this replenishment. Laboratory experiments have shown that the radiation explosion of water ice mixed with carbon-rich materials can produce both carbon dioxide and carbon monoxide. However, observations from the Voyager II flyby and other recent discoveries suggest that the interactions behind radiolysis may be limited because the axis of Uranus’ magnetic field and the orbital plane of its moons are offset by about 58 step.
Scientists concluded that most of the carbon dioxide could come from chemical processes that take place in the ocean below the surface. These compounds likely reach Ariel’s surface through cracks in the moon’s icy crust. In addition, the new observations suggest that Ariel’s surface may contain carbonate minerals, which can only be formed by the interaction of liquid water with rocks.
Źródło: Johns Hopkins Applied Physics Laboratory, Space.com, fot. NASA/ JPL/ CC0
2024-08-08 11:33:20
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