Aurora<\/a> on Earth is caused by a stream of charged particles emanating from the Sun \u2013 known as the \u2018solar wind\u2019 \u2013 hitting Earth\u2019s upper atmosphere<\/p>\n But Mercury<\/a> has only a very thin atmosphere \u2013 known as an \u2018exosphere\u2019 \u2013 and this enables solar winds to interact directly with the planet\u2019s surface, causing x-ray aurora.<\/p>\n Bepi Colombo launched in October 2018 and in June 2023 sent back a series of flyby images of Mercury<\/a>.<\/p>\n The spacecraft made its first Mercury flyby in October 2021, and an international team of planetary scientists have studied data from that flyby and published a paper on the results in the Nature Communications<\/em> science journal.<\/p>\n Bepi Colombo is actually made of two separate craft: the Mercury Planetary Orbiter led by ESA, and the Mercury Magnetospheric Orbiter (MMO) led by the Japan Aerospace Exploration Agency (JAXA).<\/p>\n During the first Mercury flyby, Bepicolombo flew as close as 200km above the surface and the MMO was able to study various types of charged particles in the solar wind around the vicinity of the planet.<\/p>\n BepiColombo approached Mercury from the night side of the northern hemisphere and then made a close approach near the morning side of the southern hemisphere.<\/p>\n The spacecraft\u2019s instruments observed the structure and boundaries of the magnetosphere, and data also showed the magnetosphere was very compressed, which study authors say could be due to high pressure conditions in the solar wind.<\/p>\n High energy electrons from the solar wind rain down on Mercury\u2019s surface and, because they are not restricted by a thick atmosphere, they hit the surface and cause x-rays to be emitted, which generates aurorae.<\/p>\n Aurorae at Mercury had previously been observed by the MESSENGER mission, but the exact processes that cause the x-ray aurora had not been well understood.<\/p>\n \u201cFor the first time, we have witnessed how electrons are accelerated in Mercury\u2019s magnetosphere and precipitated onto the planet\u2019s surface,\u201d says study lead author Sae Aizawa of the Institut de Recherche en Astrophysique et Plan\u00e9tologie<\/a> (IRAP).<\/p>\n \u201cWhile Mercury\u2019s magnetosphere is much smaller than Earth\u2019s and has a different structure and dynamics, we have confirmation that the mechanism that generates aurorae is the same throughout the Solar System.\u201d<\/p>\n![\""A\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2023\/06\/bepi-colombo-mercury-flyby-02-5cbf73d.jpg?quality=90&resize=620%2C413"\" "\\"\"A\\"\/")
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