There may be some hidden oceans lurking around Uranus.
New evidence suggests that one or two of the gas giants 27 known months there may be liquid oceans beneath their rough rock-and-ice exteriors. Possible culprits for seeding the space around Uranus with plasma are Miranda and Ariel, one or both of which could explode with oceanic plumes.
The data, which comes from the Voyager 2 mission that flew the planet into outer space nearly 40 years ago – the only spacecraft ever to do so – makes a good case for sending another probe to Uranus.
“We’ve been making the case for several years that energetic particle and electromagnetic field measurements are important not only for understanding the space environment but also for contributing to broader planetary science investigations. ,” said astronomer Ian Cohen of the Johns Hopkins Applied Physics Laboratory.
“It turns out that can be the case for data older than mine. It just shows how important it is to go into a system and explore it directly.”
Cohen and his team presented their findings March 16 at the 54th Lunar and Planetary Science Conferenceand a paper describing them has been accepted for publication in Geophysical Research Letters.
When Voyager 2 made its flyby of Uranus in 1986, it Low-Energy Charged Particle Instrument someone took something different: charged particles which seems to be trapped specific regions of the Uranian magnetosphere. They should have spread out, but they remained confined to the equator, near the orbits of Miranda and Ariel.
at the time, scientists believed whose unique profile indicates an injection of energetic electrons from a source such as a substorm in the magnetic field of Uranus. But on a closer look, Cohen and his colleagues found that the electrons did not exhibit the characteristics expected of a substorm injection.
This opened a huge can of worms, because now scientists are back at square one, trying to understand where the electrons come from. Of particular interest, they say, is the pitch angle of the electrons: the angle of their velocity vector relative to the magnetic field.
To maintain the pitch angle observed by Voyager 2, a constant source of electrons is required, significant enough to overcome the scattering and loss that would occur due to plasma waves in the planetary magnetosphere.
Without a source of this nature, in the right place and at the right angle, the team determined through modeling, the pitch angle distribution of the electrons would become constant in just a few hours.
Delving deeper into the Voyager 2 data, the team looked for 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 that region.
As for what might produce those ions… well, in the 37 years since Voyager 2 visited Uranus, scientists have made some strides in that regard. Voyager 2 made a similar discovery in the space around Saturn, discovering years later in Cassini data that icy geysers formed on what we now know to be an ocean moon, Enceladus. And another similar discovery led us to Jupiter’s ocean moon Europa.
“It is unusual for energetic particle measurements to be a forerunner in the discovery of the ocean world,” said Cohen.
Which of these moons – Miranda, the smallest of the five large moons of Uranus, or Ariel, the brightest – is kind of 50-50 at this point. It could be either. Or both. Both moons show signs of relatively recent geologic resurfacing, which may be consistent with liquid material bubbling up from the interior.
But, for now, we only have one dataset. Planetary scientists are increasingly clamoring for a dedicated mission to Uranus, possibly including Neptune. The planet has so many unique quirks that learning more about it can only be a truly exciting and rewarding experience.
The possibility of soggy moons is just icing on the smelly cake.
“The data is consistent with the very exciting potential of having an active lunar ocean there,” said Cohen. “We can always do more extensive modeling, but until we have new data, the conclusion is always limited.”
The research was presented at 54th Lunar and Planetary Science Conferenceand became accepted for publication in Geophysical Research Letters.
