Uranus’s moons may have active oceans


Griffith Observatory

Ali Hussain

A recent study led by Johns Hopkins Applied Physics Laboratory indicated that two of Uranus’s moons may have active oceans that are releasing plasma particles into the solar system.

This assertion comes from a reassessment of data collected from flyby observations made by the Low-Energy Charged Particle instrument aboard Voyager 2 in 1986. Originally, these particles were assumed to be due to the dynamics of the system, specifically because Uranus is aligned perpendicular to the other planets of the solar system.

New investigations have led researchers to question why the plasma particles radiating from Uranus were so tightly confined near its magnetic equator. Usually, it is expected that the magnetic waves recorded off a planet would spread out around the planet’s latitude. However, this spread of particles was limited to the area around the equator where Ariel and Miranda, two of Uranus’s moons, were located.

To answer this question, the researchers at the APL used physical models that led to the conclusion that the particles were either formed through vapor plumes — which have been seen on Enceladus, Saturn’s oceanic moon — or sputtering, a process in which high-energy particles hit a surface and cause other particles to be blasted off into space.

Regardless of which of these two methods of particle expulsion is true, it seems very plausible that the source of the energy required to send those particles out into space to be picked up Voyager 2 would be caused by the same thing: one or both icy moons may possess a liquid ocean beneath their frozen surface that’s actively blasting plumes of material into space.

The team presented its results at the annual Lunar and Planetary Science Conference on March 16 and had its research greenlit for publication in the journal Geophysical Research Letters.

“It isn’t uncommon that energetic particle measurements are a forerunner to discovering an ocean world,” Ian Cohen, a space physicist at APL and the lead author of the new study, said.

Previous plasma particle analyses were made in the leadup to the finding that the other gaseous giants also had oceanic moons. Jupiter had its oceanic moon Europa and Saturn had Enceladus.

Uranus’s five largest moons were already suspected of having subsurface oceans. Images from the same Voyager 2 exploration that sparked this study showed signs of geological reshaping, possibly caused by the movement of water along the moons’ surfaces.

“The data are consistent with the very exciting potential of there being an active ocean moon there,” Cohen said. “We can always do more comprehensive modeling, but until we have new data, the conclusion will always be limited.”