A new study finds that two of Uranus’ moons may have active oceans that are pumping material into space.
Realizing that there may be more events in Uranus More than previously thought, it came from the discovery of strange features in radiation data collected by NASA Voyager 2 spacecraft as it passed the planet nearly four decades ago.
The new findings, related to the moons Ariel and Miranda, also support the idea that the five largest satellites of Uranus They could have subsurface oceansan idea suggested by the Voyager 2 flyby observations.
Related: Pictures of Uranus, the tilted giant planet
The study team examined radiation and magnetic data collected by the spacecraft in 1986, long before it made its way to outside the solar system.
Recently reported observations of Voyager 2 — the only spacecraft currently to visit Uranus — show that one or two of the ice giant’s 27 known moons are adding plasma particles to the Uranus system. The discovery came in the form of “trapped” energetic particles detected by the spacecraft as it left the icy giant.
The mechanism by which Miranda and/or Ariel could do this is currently unknown, but there is a very likely possible reason: one or both of the icy moons may have a liquid ocean beneath their frozen surface that is actively blasting plumes of material into space. .
Similar particle-emitting moons exist around fellow solar system ice giant Neptune, Uranus, and gas giants Jupiter and Saturn. in the case of Jupiter’s moon Europa and Saturn EnceladusIt was an examination of the particle and magnetic field data that provided the first indications that these were ocean moons.
“It’s not uncommon for energetic particle measurements to be groundbreaking for ocean world discovery,” said study lead author Ian Cohen, an astronomer at Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland. a permit (Opens in a new tab).
“We made this case a few years ago, measurements of energetic particles and the electromagnetic field are important not only for understanding the space environment but also for contributing to larger planetary science,” Cohen added. “It turns out that this can be the case for data older than I am. It just goes to show how important it is to go into a system and explore it first-hand.”
Related: Why scientists want NASA to send a pioneering mission to Uranus
Another look at Uranus and its moons
The results will only reinforce the desire of planetary scientists to send spacecraft to Uranus and Neptune to gather more data, which has led to the $4.2 billion proposal. The main mission of Uranus NASA’s next major planetary mission.
This mission won’t be ready for launch until the early 2030s, so in the meantime, researchers have been delving into old data collected during the Voyager 2 flyby to make new discoveries.
The data Cohen and the team examined were collected by APL-built low energy charged particles (LECP) An instrument on Voyager 2, which marked the group of trapped particles.
“What’s interesting is that these particles were confined very close to Uranus’ magnetic equator,” Cohen said. This was strange, he explained, because magnetic waves within the system normally cause the particles to scatter, but they were all packed together near the planet’s equator, between Ariel and Miranda.
The team had to eliminate the possibility that the crowded particles detected by Voyager 2 were caused by the spacecraft flying through a plasma stream from the tail of Uranus’ magnetosphere. They determined that, in this case, the feature would have a wider spread of particles than was detected by Voyager 2, allowing them to rule this out as an explanation for the unusual data feature.
Cohen and the team then set out to explore simple physical models using knowledge about them ocean moons It has been developed and acquired since Voyager 2 flew by Uranus 37 years ago to recreate data collected by the spacecraft. This showed them that the advantage could only come from a strong, stable particle source, with a specific mechanism for activating it.
They ruled out other possible explanations, coming to the theory that the trapped particles come from at least one of Uranus’ moons, with Ariel and/or Miranda being the prime suspects. The team believes the particles were ejected in a vapor plume similar to the one seen Erupting from Enceladus. Another possible ejection mechanism is “sputtering,” a process in which high-energy particles collide with a surface, knocking out other particles into space.
“Right now it’s 50-50, whether it’s one or the other,” Cohen said, referring to the hypotheses scattered about.
Whatever ejection mechanism is at work in the Uranus system, the mechanism that gives these particles their energy is pretty much the same.
This activation mechanism is likely a continuous stream of particles pouring from the moons into space, generating electromagnetic waves. These waves then accelerate a small fraction of these particles to an energy large enough for them to be detected by the LCEP instrument. This process would also keep the particles trapped and thus tightly confined, just as Voyager 2 saw it.
More data must be collected from the region around Uranus before scientists can definitively determine that the particles come from the subterranean oceans of Ariel and/or Miranda.
“The data is consistent with the very exciting possibility of an active ocean moon out there,” Cohen concluded. “We can always do more extensive modeling, but until we get new data, the result will always be limited.”
Team results (Opens in a new tab) They were presented at the 54th Annual Lunar and Planetary Science Conference on March 16 and have been accepted for publication in the journal Geophysical Research Letters.
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