Uranus is more normal than we thought
NASA/Space Telescope Science Institute
Uranus’ strange magnetic field may be much less strange than astronomers first thought, and it could mean that Uranus’ largest moon is much more active and perhaps even has a global ocean It means that there is.
The only direct measurement of Uranus’s magnetic field was obtained by NASA’s Voyager 2 spacecraft, which flew close to the planet in 1986. The spacecraft’s measurements suggested that the magnetic field was biased, meaning it was not aligned with the planet’s rotation, and that it was an anomalous field. It is rich in highly energetic electrons and lacks the plasma that is common in the magnetic fields of other gas giant planets like Jupiter. Astronomers at the time thought the results were so strange that they either invoked complex physics to explain the measurements or simply dismissed them as evidence that Voyager 2’s instruments had gone awry.
Now, Jamie Jasinski and his colleagues at NASA’s Jet Propulsion Laboratory in California are reanalyzing the Voyager 2 data and finding that a rare explosion of solar wind that crushed Uranus’ magnetic field just before the spacecraft arrived may have caused the data to disappear. It was discovered that the measurements had been distorted. This means everything we thought we knew about Uranus’ magnetic field may be wrong, Jasinski says. “This is almost like resetting everything,” he says.
Jasinski and his team found that the solar wind compressed Uranus’s magnetic field to a size that typically occurs only 4 percent of the time. But for the past 40 years, scientists have assumed that’s the normal state of affairs. Jasinski said that previous strange results, such as the lack of plasma and high-energy electrons, could be explained by the squashed magnetic field.
If there is indeed plasma in Uranus’ magnetic field, and Voyager 2 just happened to miss it, it’s possible that not all of it came from the planet itself. Some may have come from the moons of Uranus, the largest of which are called Titania and Oberon. Until now, these moons were thought to be inert, but new research leaves open the possibility that they may be geologically active after all. This is consistent with recent calculations that suggest there may be a hidden ocean on the moon. “The solar wind may have wiped out all evidence of an active satellite just before the flyby occurred,” Jasinski said.
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