Mars endured an unprecedented solar superstorm, and European Space Agency (ESA) orbiters, the Mars Express and ExoMars Trace Gas Orbiter, captured the chaos, highlighting the Red Planet’s radiation dangers.
When the storm hit Earth in May 2024, it produced brilliant auroras remarkably close to the equator, and its impact on Mars was no less significant. ESA’s Mars orbiters recorded massive doses of radiation, delivering 200 days’ worth in a mere 64 hours, according to a new paper published in Nature Communications—far more than has ever been recorded before.
Mars Flooded with Solar Radiation
“The impact was remarkable: Mars’s upper atmosphere was flooded by electrons,” says lead author and ESA Research Fellow, Jacob Parrott. “It was the biggest response to a solar storm we’ve ever seen at Mars.”
The storm consisted of three separate events, all of which the team observed. These included a radiation flare, a high-energy particle burst, and a coronal mass ejection. As the high-energy, magnetized plasma and radiation from these events hit the Martian atmosphere, they stripped electrons from neutral atoms, filling the sky with charged particles.
The solar storm’s effects were most clearly felt in two layers of the Martian atmosphere, one at 110 kilometers above the surface and the other at 130 kilometers. The lower level saw a 45% increase in electrons, while the higher layer experienced an unprecedented 278% increase.
“The storm also caused computer errors for both orbiters – a typical peril of space weather, as the particles involved are so energetic and hard to predict,” adds Parrott. “Luckily, 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.”
Radio Occultation
ESA is pioneering a technique called radio occultation, utilizing multiple platforms to investigate the Martian atmosphere. Presently, the technique is used with Earth-orbiting satellites, but the team is working to bring it to other planets in our solar system.
The radio occultation process begins with Mars Express sending a signal to the Trace Gas Orbiter just as it vanishes over the horizon. That disappearance is key to the process, bending the signal through layers of the atmosphere on its way to the Trace Gas Orbiter and providing information about those layers along the way. To complete the work, the team confirmed their electron density measurements using NASA’s MAVEN orbiter.
“This technique has actually been used for decades to explore the Solar System, but using signals beamed from a spacecraft to Earth,” said co-author Colin Wilson, ESA project scientist for Mars Express and TGO. “It’s only in the past five years or so that we’ve 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’s great to see it in action.”
Earth and Mars
Analyzing the data brings differences between our world and its neighbor, Mars, into clearer focus. Earth’s magnetic field shields our planet, mitigating some of space weather’s strongest effects. That shielding minimized the effects of the 2024 storm in the upper atmosphere while diverting many particles either to the poles or away from the planet entirely.
“Being exposed to the solar flare covered in the article whilst being unprotected would be like getting the worst sunburn of your life in a couple of seconds,” Parrott explained to The Debrief. “However, people are not going to be walking around in short sleeves on the Martian surface for many centuries. So whilst we have our space suits, a thicker ionosphere doesn’t affect the safety of humans much.”
“However, the ionosphere is critical for communications. Sometimes our links to the surface are blocked by ionospheric phenomena,” Parrott continued. “So future missions must be equipped with relay equipment capable of totally different frequency bands, as the frequency of the transmission can affect how a signal travels through the ionosphere.”
“Possible other refinements might be implementing “solar flare blackout” periods in communication scheduling as there is no point using power to transmit to a rover or base on the surface when the ionosphere is going to block all the signals,” Parrott concluded.
“If Mars’s upper atmosphere is packed full of electrons, this could block the signals we use to explore the planet’s surface via radar,” Colin said, “making it a key consideration in our mission planning – and impacting our ability to investigate other worlds.”
With life support infrastructure necessary for mere survival on Mars, this highly radiation- and space-weather-susceptible environment will require further study ahead of any crewed missions.
The paper, “Martian Ionospheric Response During the May 2024 Solar Superstorm,” appeared in Nature Communications on March 5, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.