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\t\t\t\t\t\t05\/03\/2026<\/span> What happens when a solar superstorm hits Mars? Thanks to the European Space Agency\u2019s Mars orbiters, we now know: glitching spacecraft and a supercharged upper atmosphere.<\/p>\n<\/div>\n In May 2024, Earth was hit by the biggest solar storm recorded in over 20 years. It sent our planet\u2019s atmosphere into overdrive, triggering shimmering auroras that were seen as far south as Mexico.<\/p>\n This storm also hit Mars. Fortunately, ESA\u2019s two Mars Orbiters \u2013 Mars Express and ExoMars Trace Gas Orbiter (TGO) \u2013 were in the right place at the right time, with a radiation monitor aboard TGO picking up a dose equivalent to 200 \u2018normal\u2019 days in just 64 hours.<\/p>\n A new study published today in Nature Communications<\/i>\u00a0now reveals in greater depth how this intense, stormy activity affected the Red Planet.<\/p>\n<\/p><\/div>\n \u201cThe impact was remarkable: Mars\u2019s upper atmosphere was flooded by electrons,\u201d says ESA Research Fellow Jacob Parrott, lead author of the study. \u201cIt was the biggest response to a solar storm we\u2019ve ever seen at Mars.\u201d<\/p>\n The superstorm caused a dramatic increase in electrons in two distinct layers of Mars\u2019s atmosphere at altitudes of around 110 and 130 km, with numbers rising by 45% and a whopping 278%, respectively. This is the most electrons we\u2019ve ever seen in this layer of martian atmosphere.<\/p>\n \u201cThe storm also caused computer errors for both orbiters \u2013 a typical peril of space weather, as the particles involved are so energetic and hard to predict,\u201d adds Jacob. \u201cLuckily, the spacecraft were designed with this in mind, and built with radiation-resistant components and specific systems for detecting and fixing these errors. They recovered fast.\u201d<\/p>\n To investigate the superstorm\u2019s impact on Mars, Jacob and colleagues used a technique currently being pioneered by ESA known as radio occultation.<\/p>\n<\/p><\/div>\n First, Mars Express beamed a radio signal to TGO at the very moment it was disappearing over the martian horizon. As TGO vanished, the radio signal was bent (\u2018refracted\u2019) by the various layers of Mars\u2019s atmosphere before being picked up by the orbiter, allowing scientists to glean more about each layer. The researchers also used observations from NASA\u2019s MAVEN mission to confirm the electron densities.<\/p>\n \u201cThis technique has actually been used for decades to explore the Solar System, but using signals beamed from a spacecraft to Earth,\u201d says Colin Wilson, ESA project scientist for Mars Express and\u00a0TGO, and co-author of the study. \u201cIt\u2019s only in the past five years or so that we\u2019ve started using it at Mars between two spacecraft, such as Mars Express and TGO, which usually use those radios to beam data between orbiters and rovers. It\u2019s great to see it in action.\u201d<\/p>\n ESA uses orbiter-to-orbiter radio occultation routinely at Earth, and plans to use it more regularly in future planetary missions.<\/p>\n<\/p><\/div>\n The superstorm was experienced very differently at Earth and Mars, highlighting the differences between the two worlds.<\/p>\n At Earth, the response of the upper atmosphere was more muted, thanks to the shielding effect of Earth\u2019s magnetic field. As well as deflecting a lot of solar storm particles away from Earth, the magnetic field also diverted some towards Earth\u2019s poles, where they caused the sky to light up with auroras.<\/p>\n<\/p><\/div>\n While their differences can make it tricky to compare planets directly, understanding how solar activity impacts the residents of the Solar System \u2013 in other words, space weather forecasting \u2013 is hugely important. At Earth, solar storms can be dangerous and damaging for astronauts and equipment up in space, and can disrupt our satellites and systems (power, radio, navigation) further down.<\/p>\n However, studying space weather is difficult as the Sun throws out radiation and material erratically, making targeted measurements largely opportunistic. \u201cFortunately, we were able to use this new technique with Mars Express and TGO just 10 minutes after a large solar flare hit Mars. Currently we\u2019re only performing two observations per week at Mars, so the timing was extremely lucky,\u201d adds Jacob.<\/p>\n Jacob and colleagues captured the aftermath of three solar events \u2013 all part of the same storm, but different in terms of what they throw out into space, and how they do it: one flare of radiation, one burst of high-energy particles, and an eruption of material known as a coronal mass ejection (CME).<\/p>\n Together, these events sent fast-moving, energetic, magnetised plasma and X-rays flooding towards Mars. When this barrage of material hit the planet\u2019s upper atmosphere it collided with neutral atoms and stripped away their electrons, causing the region to fill up with electrons and charged particles.<\/p>\n<\/p><\/div>\n \u201cThe results improve our understanding of Mars by revealing how solar storms deposit energy and particles into Mars\u2019s atmosphere \u2013 important as we know the planet has lost both\u00a0huge amounts of water\u00a0and\u00a0most of its atmosphere\u00a0to space, most likely driven by the continual\u00a0wind of particles\u00a0streaming out from the Sun,\u201d says Colin.<\/p>\n \u201cBut there\u2019s another side to it: the structure and contents of a planet\u2019s atmosphere influence how radio signals travel through space. If Mars\u2019s upper atmosphere is packed full of electrons, this could block the signals we use to explore the planet\u2019s surface via radar, making it a key consideration in our mission planning \u2013 and impacting our ability to investigate other worlds.\u201d<\/p>\n<\/p><\/div>\n \u2018Martian ionospheric response during the May 2024 solar superstorm\u2019\u00a0by J. Parrott et al. is published today in\u00a0Nature Communications<\/i>. DOI: 10.1038\/s41467-026-69468-z<\/p>\n Jacob Parrott began this work as an ESA\u00a0Young Graduate Trainee, continued it as a postgraduate student at Imperial College London, and is now a Research Fellow at\u00a0ESA\u2019s European Space Research and Technology Centre (ESTEC)\u00a0in the Netherlands.<\/p>\n The May 2024 solar storm was monitored and observed after it struck Earth by numerous ESA missions and covered in a number of subsequent web stories, including:<\/p>\n Several ESA missions are either currently or soon-to-be keeping an eye on our star.\u00a0ESA\u2019s Solar Orbiter\u00a0is continuously observing the Sun up close and tracking its activity (including\u00a0the May 2024 superstorm). Solar Orbiter will soon be joined by\u00a0Smile, a mission to understand how Earth\u2019s magnetic field responds to the solar wind scheduled to launch in spring 2026, and later by\u00a0Vigil\u00a0(2031), which will spot potentially hazardous solar activity in near-real-time.<\/p>\n The initial dose of radiation delivered to Mars orbit by the solar storm, measured by TGO in May 2025, was reported in Semkova et al.:\u00a0doi.org\/10.1016\/j.lssr.2025.02.010<\/p>\n For more information please contact:<\/b><\/p>\n \nESA Media Relations
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\n\t\t\t\n\t\t<\/div>\n<\/p><\/div>\nPioneering a new technique<\/b><\/h3>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\nDifferent worlds, different weather<\/b><\/h3>\n
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media@esa.int<\/p>\n<\/p><\/div>\n