Discovery of Hidden Ocean Beneath Uranus’ Moon Miranda Could Challenge Views on Habitability in Our Solar System

A new study suggests that Uranus’ moon Miranda may have an ocean of water beneath its surface, a discovery that challenges many assumptions about the moon’s history and composition and could put it in the company of a few worlds in the our solar system with potentially habitable environments. . “It’s surprising to find evidence of an ocean in a small object like Miranda,” said Tom Nordheim, a planetary scientist at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, and co-author of the study. published in The. Journal of Planetary Science.

“It helps build the story that some of these moons near Uranus could be very interesting, that there could be multiple oceanic worlds around one of the outermost planets in our solar system, which is both exciting and strange. ” Among the moons in the solar system, Miranda stands out. The few images captured by Voyager 2 in 1986 show that Miranda’s southern hemisphere (the only part we have seen) is a Frankenstein-like mixture of rutted terrain marked by jagged scars and cracked areas, like squares on a quilt. Most researchers suspect that these strange structures are the result of tidal forces and heating inside the moon. Caleb Strom, a doctoral candidate at the University of North Dakota who worked with Nordheim and Alex Patthoff of the Planetary Science Institute in Arizona, reanalyzed the Voyager 2 images. The team tried to explain Miranda’s enigmatic geology by reverse engineering its surface features to determine what internal structure the moon must have had to form the lunar geology in response to the tides.

After first mapping several surface features such as craters, ridges and Miranda’s unique trapezoidal coronae, the team developed a computer model to test different possible structures on the moon’s interior, making comparison of the expected stress patterns with the actual surface geology. The configuration that provided the best match between the predicted pressure patterns and the observed surface features called for the existence of a large ocean beneath the icy surface of Miranda about 100-500 million years ago. According to the study, this subterranean ocean was at least 100 kilometers deep and hidden under an ice sheet no more than 30 kilometers thick. Since Miranda has a radius of only 235 kilometers, the ocean would have filled almost half of the moon’s body. “That result was a big surprise for the team,” Strom said.

The researchers believe that tidal forces between Miranda and the nearby dunes were extremely important in the creation of that ocean. These constant gravitational forces can be amplified by orbital resonances, an arrangement in which the period of each moon around a planet is an exact complement of the periods of the other. For example, the moons of Io and Europa have a 2:1 resonance: For every two orbits that Io makes around Jupiter, Europa makes just one, resulting in tidal forces that known to hold an ocean beneath Europa’s surface. These orbit configurations and the resulting tidal forces deform the moon like rubber balls, creating friction and heat that keep the interior warm. This also creates pressures that crack the surface, creating a rich variety of geological features. Numerical simulations suggest that Miranda and her neighbors may have had similar feelings in the past. This provides a mechanism that could have heated Miranda’s interior to create and maintain a surface ocean.

At some point, the moon’s orbital ballet slowed down, slowing the warming process and causing the moon’s interior to cool and solidify. But the team doesn’t think Miranda’s insides are completely frozen yet. If the ocean were completely frozen, Nordheim explained, it would have expanded and created distinct cracks on the surface, but there aren’t any. This suggests that Miranda is still cooling and may even now have an ocean below the surface. Miranda’s current ocean may be relatively thin, Strom said. “But the suggestion of an ocean in one of the most distant moons in the solar system is amazing,” he said. Miranda was not expected to have an ocean. Because of its small size and old age, scientists science thought it was a frozen ball. The heat left over from creation was believed to have disappeared long ago. But Patthoff pointed out that predictions about a frozen moon can be wrong, as which is seen by Saturn’s moon Enceladus.

Before the Cassini spacecraft arrived in 2004, many scientists believed that Enceladus was a frozen ball of ice and rock. But in reality there was a global ocean and active geological processes. “Very few scientists expected Enceladus to be geologically active,” Patthoff said. “But right now, water vapor and ice are burning out of the Southern Hemisphere. ” Enceladus is now a prime target in the search for life beyond Earth. Miranda could be a similar case. Miranda is similar in size and composition to Enceladus and, according to a 2023 study led by APL’s Ian Cohen, Miranda would be actively shooting material into space. If there is (or even was) an ocean, it could be a future target for studying habitability and life. However, Nordheim warns that we still don’t know enough about Miranda and the Uranian moons to speculate about the existence of life. “We won’t know for sure if there’s an ocean until we go back and collect more data,” he said. “We’re getting the last piece of science we can from the Voyager 2 images For now , we’re excited about the moon pictures. For now, we’re excited about the possibilities and want to get back to exploring Uranus and the possible oceans.”

The secrets of the frozen moon Uranus revealed

The icy moons of Uranus have intrigued scientists since Voyager 2 captured stunning images and valuable data about them during their brief flyby in 1986. This latest research, led by Caleb Strom and APL’s Tom Nordheim, as part of a broader effort by APL to recover the discovery. the secrets of these mysterious moons and the strange planet they orbit:

• 2023: A team led by APL’s Ian Cohen re-analyzed particle and magnetic data from the Voyager 2 spacecraft and found that Uranus’ moons Ariel and Miranda may both be releasing material into the space environment around Uranus, perhaps through Pluto.
• 2024: APL’s Richard Cartwright used observations of Ariel, a moon of Uranus, by NASA’s James Webb Space Telescope to conclude that the moon may have a subsurface ocean that replenishes its deposits of carbon dioxide ice. surface – a topic he brought up at the recent meeting. of the American Astronomical Society.

Source: Phys.org/Johns Hopkins University Applied Physics Laboratory