Two European Space Agency Mars orbiter missions, the Mars Express and ExoMars Trace Gas Orbiter spacecraft, watched as a powerful solar “superstorm” that ravaged Earth also hit the Red Planet. The storm caused failing spacecraft and a supercharged atmosphere in upper Mars.
The solar storm struck Earth on May 11, 2024, proving to be the largest recorded on our planet in over 20 years. It generated desire northern lightsusually confined to the poles of the planet, as far towards the equator as Mexico. And indeed, the storm also affected Marchwith Mars Express and that ExoMars Trace Gas Orbiter (TGO) belt with 200 days of radiation in just 64 hours.
The solar storm increased the number of electrons in two layers of the Martian atmosphere: a 45% increase at an altitude of 110 kilometers and a whopping 278% increase at 130 kilometers above the Martian surface. That represents the most electrons planetary scientists have ever seen in the Red Planet’s atmosphere.
The solar superstorm also demonstrated the negative impact such space weather can have on space technology, a risk that drives scientists’ desire to develop better space weather prediction.
“The storm also caused data errors for both orbiters – a typical hazard of space weather, as the particles involved are so energetic and difficult to predict,” continued Parrott. “Fortunately, the spacecraft were designed with this in mind, and built with radiation-resistant components and specific systems to detect and fix these failures. They recovered quickly.”
Parrott and colleagues used a pioneering technique called radio occultation to investigate the effects of this solar storm. This involved Mars Express sending a radio signal to TGO as it dipped below the horizon of Mars. This signal was then refracted back at Mars Express by the atmospheric layers of the Red Planet. This revealed details about these layers.
“This technique has actually been used for decades to explore the solar system, but using signals sent from a spacecraft to Earth,” said team member Colin Wilson, ESA project scientist for Mars Express and TGO. “It’s only in the last five years or so that we’ve started using it on Mars between two spacecraft, like Mars Express and TGO, which typically use these radios to send data between orbiters and rovers. It’s great to see it in action.”
What this revealed was the fact that Earth and Mars reacts very differently when bombarded from charged particles from the Sun.
Solar storms affect Mars and Earth differently
The main difference between Mars and Earth in their response to solar storms is the fact that our planet has a protective magnetic field, the magnetosphere. This dampens the impact of solar storms on our atmosphere and also directs charged particles away both from Earth and towards the poles, where they can cause auroras.
The lack of a magnetosphere around Mars makes it difficult to compare the Red Planet with Earth. The study of space weather around our neighboring planet is also complicated by the fact that the sun is erratic in the distribution of charged particles and radiation.
“Fortunately, we were able to use this new technique with Mars Express and TGO just 10 minutes after a large solar flare hit Mars,” explained Jacobs. “Currently, we only perform two observations per week on Mars, so the timing was extremely fortunate.”
The researchers looked at the aftermath of three solar events that were part of the same parent storm: a radiation flare, an explosion of high-energy charged particles, and material launched by a coronal mass ejection (CME). When the radiation and material from these events hit the Martian atmosphere, electrons were stripped from neutral atoms, causing these negatively charged particles to fill the atmosphere in numbers never before recorded.
The team’s study of the event may also help us understand how the Red Planet became a dry and barren landscape.
“The results improve our understanding of Mars by revealing how solar storms deposit energy and particles in the Martian atmosphere – importantly, as we know, the planet has lost both vast amounts of water and most of its atmosphere to space, most likely driven by the continuous wind of particles streaming out from the Sun,” Wilson added. “But there’s another side to it: the structure and content of a planet’s atmosphere affects how radio signals travel through space. “If Mars’ upper atmosphere is packed with electrons, this could block the signals we use to explore the planet’s surface via radar, making it a key consideration in our mission planning – and affect our ability to probe other worlds.”
The team’s results were published Thursday (March 5) in the journal Nature communication.
