April 17, 2024

Mercury Looks Like It Has Its Own Curious Aurora After All : ScienceAlert

A probe was sent to study the sadly neglected The outermost planet in the Solar System has revealed hearing processes that occur despite an almost non-existent atmosphere.

In October 2021, the BepiColombo probe measured electrons and ions at Mercury, finding evidence of its acceleration. The analysis showed that this was the result of auditory comprehension processes related to Magnetic field of mercuryultimately producing a small X-ray emission.

This means that aurorae are now visible on every single planet, suggesting that a mechanism for aurora production may be universal throughout the Solar System, despite the large differences between the planets.

Mercury hides some interesting secrets behind his gray face… (NASA/JHUAPL/Arizona State University/Carnegie Institution of Washington)

“Here, we show the direct evidence that strongly supports the view that energetic electrons are accelerating in the near-tail region of Mercury’s magnetosphere, rapidly disappearing toward the dawn sectors, and are injected into followed by closed magnetic field lines on the planetary night side,” writes a team led by astrophysicist Sae Aiwaza of the University of Pisa in Italy.

“These observations demonstrate that electron injections and subsequent energy-dependent currents observed across the Solar System that generate aurorae are a universal mechanism despite differences in the structure and dynamics of planetary magnetospheres.”

In general, it is thought that two things are needed to produce this type of aurora: a magnetic field, and atmosphere. Particles are accelerated along magnetic field lines to a polar region, where they rain down into the atmosphere. Then the interactions of the charged particles with atoms and other molecules release electromagnetic radiation, which we can see as a colorful glow.

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The charged particles come mostly from the solar wind, although Jupiter’s powerful, permanent aurorae are fueled mostly by electrons from its volcanic moon Io.

But Saturn also has aurorae powered by the solar wind, which does Uranus. Golden features were seen on Neptune by Voyager 2 in 1989, but nothing was discovered after that, so we don’t have a good characterization of them.

Mars and Venus were expected to have no aurorae, as they lack global magnetic fields, but both planets surprised us. Mars has patches of magnetism on its surface that produce local patches of aurora in the sky. And on Venus, magnetic fields from the Sun seems to help the beginning of the atmospheric dawn.

Mercury has a global magnetic field, but it is quite weak. In addition, because Mercury is so close to the Sun, it is constantly exposed to radiation and the solar wind. So the planet has no real atmosphere to speak of; he has a thin exosphere kicked up by solar wind and micrometeoroid bombardment. This exosphere is gravitationally bound to the planet, but too diffuse to behave as a gas.

Because of this, scientists thought it unlikely that Mercury would have an aurora. And it is also, scientists found, a surface sometimes fluorescence in X-rays.

Illustration of the electron rain observed by BepiColombo. (Sae Aizawa)

Aizawa and her colleagues used it BepiColombo to track electrons in the vicinity of Mercury, and found evidence of an acceleration in the planet’s magnetic field lines, precipitating towards the surface in areas, they found, consistent with the observed X-ray fluorescence. The fluorescence, they also found, is consistent with what we would expect from this electron shower.

So even without atmosphereand with a wimpy little magnetic fieldMercury seems to have found a way to create strange mercury aurorae, all its own, in minerals that fluoresce X-radiation on the surface.

The research is published in Nature Communication.

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