There could be hidden oceans around Uranus.
New evidence suggests that one or two of the gas giants 27 known moons could harbor liquid oceans beneath their crusty exteriors of rock and ice. Possible culprits for seeding the space around Uranus with plasma are Miranda and Ariel, one or both of which could erupt with ocean plumes.
The data, which comes from Mission Voyager 2 which flew past the planet en route to space nearly 40 years ago – the only spacecraft to ever do so – makes a strong case for sending another probe to Uranus.
“We have been explaining for a few years now that measurements of energetic particles and electromagnetic fields are important not only for understanding the space environment, but also for contributing to the greater planetary scientific investigation,” he added. said astronomer Ian Cohen of the Johns Hopkins Applied Physics Laboratory.
“It turns out that this can even be the case for data older than me. It shows how useful it can be to access a system and explore it first-hand.”
Cohen and his team presented their findings March 16 at the 54th Lunar and Planetary Science Conferenceand an article describing them has been accepted for publication in Geophysical Research Letters.
When Voyager 2 performed its flyby of Uranus in 1986, its Low energy charged particle instrument picked up something special: charged particles who seemed to be trapped in specific regions of the Uranian magnetosphere. They should have expanded, but they remained confined to the equator, near the orbits of Miranda and Ariel.
At the time, scientists believed that the particular profile indicated an injection of energetic electrons from a source such as a sub-storm in the magnetic field of Uranus. But on closer inspection, Cohen and his colleagues discovered that the electrons do not exhibit the characteristics expected from a substorm injection.
This opened up a huge Pandora’s box, because now scientists were back to square one, trying to figure out where the electrons came from. Of particular interest, they said, was the pitch angle of the electrons: the angle of their velocity vector relative to the magnetic field.
In order to maintain the pitch angle observed by Voyager 2, a constant source of electrons would be needed, large enough to overcome the scattering and loss that would occur due to plasma waves in the planetary magnetosphere.
Without such a source, in the right place and at the right angle, the team determined by modeling, the pitch angle distribution of the electrons would become uniform in just a few hours.
Digging deeper into Voyager 2 data, the team sought out such a source. Their modeling showed a clear and unmistakable maximum in the space between Miranda and Ariel, suggesting a source of energetic ions in this region.
As for what might be generating these ions… well, in the 37 years since Voyager 2 visited Uranus, scientists have made progress in this regard. Voyager 2 made a similar detection in space around Saturn, discovered several years later in Cassini data generated by icy geysers on what we now know is an oceanic moon, Enceladus. And another similar detection led us to Jupiterthe ocean of the moon Europa.
“It is not uncommon for energetic particle measurements to be a precursor to the discovery of an ocean world,” Cohen says.
As for which moon it is – Miranda, the smallest of Uranus’ five major moons, or Ariel, the brightest – it’s a bit of a 50-50 at this point. It could be one or the other. Or both. Both moons show signs of relatively recent geologic resurfacing, which could be consistent with an eruption of liquid matter from within.
But, so far, we only have one set of data. Planetary scientists are increasingly calling for a mission dedicated to Uranus, possibly with Neptune included. The planet has so many weird quirks that learning more about it could only be a truly exciting and rewarding experience.
The possibility of soggy moons is just icing on the cake stinky cake.
“The data is consistent with the very exciting potential of having an active ocean moon there,” Cohen says. “We can always do more complete modeling, but until we have new data, the conclusion will always be limited.”
The research was presented at the 54th Lunar and Planetary Science Conferenceand was accepted for publication In Geophysical Research Letters.