A new study suggests that Uranus’ moon Miranda may harbor an ocean of water beneath its surface; This finding challenges many assumptions about the moon’s history and composition, and could place it alongside a select few worlds that could potentially be hosted in our solar system. life. supportive environment.

“Finding evidence of an ocean inside an object as small as Miranda is an incredible surprise,” said Tom Nordheim, a planetary scientist at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, and co-author of the study. inside Planetary Science Journal.

“It helps further develop the story that some of these moons of Uranus could be really interesting, that there could be multiple ocean worlds around one of the most distant planets in our solar system, which is both exciting and surprising.”

Among the satellites of the solar system, Miranda stands out. Several photographs taken by Voyager 2 in 1986 show that Miranda’s southern hemisphere (the only part we see) is a Frankenstein-like jumble of rugged landscapes punctuated by jagged outcroppings and cratered areas like squares on a quiver. Many researchers suspect that these strange structures are the result of tidal forces and the heating of the moon.

Caleb Strom, a graduate student at the University of North Dakota and working with Nordheim and Alex Pathoff of the Planetary Science Institute in Arizona, examined the Voyager 2 image. The team set out to explain Miranda’s enigmatic geology by reverse engineering its surface features, working backwards to discover how the moon’s interior structure must have shaped the moon’s geology in response to tidal forcing.

After creating an initial map of various surface features such as cracks, ridges, and Miranda’s unique trapezoidal dunes, the team developed a computer model to test various possible structures of the Moon’s interior by matching the predicted stress patterns to the actual surface geology.

The pattern that provides the best match between predicted stress patterns and observed surface properties required the existence of a large ocean beneath the Miranda ice surface approximately 100–500 million years ago. According to the study, this subsurface ocean was at least 62 miles (100 kilometers) deep and hidden beneath a shell of ice no more than 19 miles (30 kilometers) thick.

Considering that Miranda’s radius is only 146 miles (235 kilometers), ocean should fill nearly half of the Moon’s body. “This result was a big surprise for the team,” Strom said.

Researchers believe that the key to the creation of this ocean was the tidal forces between Miranda and the nearest moons. These regular gravitational pulls can be amplified by orbital resonances, a configuration in which the period of each moon around a planet is an exact integer of the periods of the others.

For example, Jupiter’s moons Io and Europa have a 2:1 resonance: For every two orbits Io makes around Jupiter, Europa makes exactly one, resulting in tidal forces known to support Europa’s subsurface ocean.

These orbital configurations and the tidal forces they cause deform the satellites like rubber balls, causing friction and heat that keeps them warm inside. It also creates stresses that crack the surface, creating a rich texture of geological features. Numerical simulations showed that Miranda and its nearby moons likely had such resonances in the past; This suggests a potential mechanism that could warm Miranda’s insides and create and sustain an underground ocean.

At some point, the moon’s orbital balance was disrupted and the warming process slowed, so the moon’s interior began to cool and solidify. However, the team does not believe that Miranda’s insides are completely frozen yet. Nordheim explained that if the ocean were to freeze completely, it would expand and cause some cracks that were not present on the surface.

This suggests that Miranda is still cooling and may even now have an ocean beneath its surface. Strom noted that Miranda’s modern ocean was probably relatively thin. “But the idea of ​​an ocean inside one of the solar system’s most distant moons is remarkable,” he said.

Miranda did not foresee the ocean. Given its small size and age, scientists thought it was probably a frozen ball of ice. It is assumed that the residual heat from its formation dissipated long ago. But as Pathoff points out, predictions about icy moons can be wrong, as Saturn’s moon Enceladus has shown.

Before the Cassini spacecraft arrived in 2004, many scientists believed that Enceladus was a frozen ball of ice and rock. But in reality it was a global ocean and active geological processes. “Very few scientists expected Enceladus to be geologically active,” Pathoff said. “But as we speak, it is expelling water vapor and ice from the southern hemisphere.” Enceladus is now one of the primary targets in the search for life beyond Earth.

Miranda may be in a similar situation. It is comparable to Enceladus in size and composition, and may be actively ejecting material into space, according to a 2023 study led by APL’s Ian Cohen. If it has (or even had) an ocean, it could be a future target for studying life and limb. But Nordheim warns that we still don’t know too much about Miranda and the moons of Uranus to predict the existence of life.

“We won’t know for sure there’s an ocean there until we go back and collect more data,” he said. “We are extracting the latest scientific information from the Voyager 2 images. For now, we are excited about the opportunities and look forward to returning to a deeper study of Uranus and its potential ocean moons.”

Secrets of Uranus’ icy moons are revealed

The icy moons of Uranus have fascinated scientists since Voyager 2 captured stunning images and valuable data during its brief flyby in 1986. This latest study, led by APL’s Caleb Strom and Tom Nordheim, is part of a broader effort at APL to unravel the mysteries of these mysterious moons and the unusual planet they orbit:

• 2023: A team led by APL’s Ian Cohen reanalyzed particle and magnetic data from Voyager 2’s flyby and found that Uranus’ moons Ariel and Miranda may be ejecting material into space around Uranus, possibly via plumes.
• 2024: Using data from observations of Uranus’ moon Ariel by NASA’s James Webb Space Telescope, APL’s Richard Cartwright concludes that the moon may have a subsurface ocean that replenishes carbon dioxide ice deposits on its surface; He presented this topic at the last meeting of the American Space Agency. Astronomical Union societies