Particle Delivery

Hold onto your butts: Uranus' moons — or at least some of them — may be a lot more liquid than once believed.

Researchers taking another look at nearly forty-year-old data collected by NASA's Voyager 2 spacecraft have discovered that energized plasma particles are being ejected into nearby space from one or two of Uranus' moons: Ariel and/or Miranda.

While the researchers haven't determined the mechanism that's driving these particles beyond their lunar boundaries, their findings so far, as detailed in a study accepted for publication in the journal Geophysical Research Letters, suggest there's a good chance that subsurface oceans could be responsible.

What caught the scientists' eye was that the particles appeared to be clumped around Uranus' magnetic equator. That's odd, because the magnetic forces should cause the particles to disperse and spread across the planet — unless, the researchers concluded, there was a steady supply of magnetized particles from a nearby moon, ejected as a vapor plume from an ocean somewhere beneath its icy exterior.

What Lies Beneath

"It isn't uncommon that energetic particle measurements are a forerunner to discovering an ocean world," study lead author Ian Cohen, an astrophysicist at John Hopkins Applied Physics Laboratory, said in a press release.

Indeed, it would be far from unprecedented for the discovery of a vast, undiscovered expanse of liquid on another moon to be based on or at least prompted by particle data — not to mention previous findings that have already suggested the presence of oceans on Uranus' largest moons.

The same technique was used to help reveal subsurface lunar oceans on both Europa, one of Jupiter's largest moons, and Saturn's frosty satellite Enceladus.

"We've been making this case for a few years now that energetic particle and electromagnetic field measurements are important not just for understanding the space environment but also for contributing to the grander planetary science investigation," Cohen explained.

"Turns out that can even be the case for data that are older than I am. It just goes to show how valuable it can be to go to a system and explore it first-hand," he added.

Return Trip

Even though the old data, collected by Voyager 2's Low-Energy Charged Particle instrument, is still yielding new findings, scientists would obviously prefer something newer to work with.

"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."

37 years later, and Voyager 2 remains the only spacecraft to visit Uranus, which makes NASA's interest in revisiting the planet all the more exciting.

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