Of all the planets in the solar system, Mercury is an oddball. Despite being closer to the Sun, it is not the hottest planet. It rotates rapidly around the Sun every 88 days in the shape of a flattened oval, but it takes an excruciating 59 days to complete one rotation on its axis. But wait, there’s more: he only clings to a radiation belt less than half the time.
Specifically, Mercury’s radiation belt exists about 50% of the time when the planet is furthest from the Sun, while it is there about 20% of the time at closer distances. in a study published yesterday in Nature AstronomyResearchers confirmed that, contrary to what has long been assumed, Mercury also has a radiation belt very similar to those of most planets encapsulated by magnetic fields. So Mercury is officially even stranger than we thought, but the findings will also inform future missions in that direction.
“When we think about future space exploration and what instruments we will send to Mercury, we will want to be aware of this radiation belt and take appropriate precautions and design around it,” study co-author Ryan Dewey, an engineer at the University of Michigan, said in a statement. statement.
An animated capsule
A planet’s magnetosphere protects it from powerful solar radiation. On Earth, the magnetosphere protects our planet from extreme solar weather by trapping high-energy particles within its magnetic field. This results in two permanent radiation belts, called Van Allen belts, that “surround the Earth like huge donuts,” according to a NASA study. explainer.
Other planets have similar protections, although the details vary depending on the physics of each planet. For example, Mars has a “weak and uneven” magnetosphere, while Jupiter’s dense magnetic field means it “barely” senses powerful events like coronal mass ejections, as NASA’s Scientific Visualization Studio notes. explained in 2019. For decades, scientists debated whether Mercury actually trapped particles in a stable belt, even though it also has a magnetic field.
It’s not an exception
That said, scientists believed this made sense, since Mercury’s weak magnetic field (about 1% the strength of Earth’s) was constantly under attack from the Sun’s tumultuous climate and magnetic extremes, according to the statement. As a result, there wouldn’t be “much room for the energetic electrons that make up the radiation to survive before being ejected into space or hitting the planet,” Dewey explained.
However, Dewey and his colleagues wondered if there was any chance that we had missed some of the old data. For the latest study, the team reviewed observations collected between 2011 and 2015 by NASA. MESSENGER spacecraft. Using more recent advanced analysis techniques, the researchers found that Mercury did indeed have a “ring-like radiation belt,” although with a lifetime typically less than 8 to 12 hours and, very occasionally, up to several Earth days.
Mercury is trying
The reason for this impermanence, according to the newspaper, is “a loss rather than a lack of supply.” In other words, Mercury, like other planets, is perfectly capable of capturing and trapping high-energy electrons. However, as previously assumed, its mere proximity to the Sun plays an important role. Still, the thing is that, like other planets, Mercury has a radiation belt. But, like other planets, its innate characteristics and environment affect how that radiation belt manifests.
The findings should be especially relevant for upcoming missions such as BepiColomboa joint mission of Europe and Japan that will arrive at Mercury in November of this year. For spaceflight operators, radiation belts can be annoying obstacles to the operation of spacecraft (and astronauts, if they are manned). In the paper, the team wrote that BepiColombo may have already crossed Mercury’s radiation belts, but its mission should give us more clues about our strange neighbor, and perhaps others like it.
“Mercury provides a natural laboratory for inferring what radiation might look like on other planets orbiting close to their stars, as well as on distant planets during extreme space weather conditions,” Weijie Sun, study co-author and astrophysicist at the University of California, Berkeley, said in the release.
