In May 2024, people worldwide witnessed beautiful aurorae that appeared far beyond Earth’s polar regions. Even the Aurora Borealis, which is usually confined to the Arctic Circle, was visible as far south as Mexico. This rare event was the result of a massive solar storm, the most powerful recorded in over 20 years. As always, this storm bombarded Earth with charged solar particles that interacted with the planet’s magnetosphere. The storm also reached Mars, which was witnessed by two orbiters operated by the European Space Agency (ESA) – the Mars Express and ExoMars Trace Gas Orbiter (TGO).

Working in tandem, the two spacecraft captured images of the event and obtained detailed information on the amount of radiation that reached Mars: the equivalent of 200 days of what is regularly exposed to in just 64 hours. The data was presented in a study published in Nature Communications, where an international team of researchers used a method pioneered by the ESA to reveal how this storm affected Mars. The results could lead to a better understanding of space weather and how solar storms interact with planets.

The technique is known as radio occultation, in which the Mars Express probe beamed a radio signal to the TGO as it disappeared over the Martian horizon. While the ESA routinely uses orbiter-to-orbiter radio occultation at Earth, this was one of the few instances in which it was used around Mars. Basically, the radio signal was refracted by layers in Mars’ atmosphere before being picked up by TGO, allowing scientists to learn more about each layer. Data from NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) mission was also used to confirm the electron densities.

*To study Mars’s atmosphere, ESA’s two Mars orbiters make use of a technique called ‘radio occultation.’ Credit:ESA*

Colin Wilson, an ESA project scientist for Mars Express and TGO and a co-author of the study, said in an ESA press release:

This technique has actually been used for decades to explore the Solar System, but using signals beamed from a spacecraft to Earth. 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.

The superstorm coincided with the hyperactive sunspot region AR3664 returning to the Sun’s Earth-facing side. The blast sent out a class X2.9 flare and a large cloud of material – aka. a Coronal Mass Ejection (CME) – towards Earth and Mars. On Mars, the storm caused a dramatic increase in electrons in two layers of its atmosphere – 110 and 130 km (68 and 80 mi) above the surface – of 45% and 278% (respectively), the most electrons that have ever been observed in this region of the Martian atmosphere. Said ESA Research Fellow Jacob Parrott, the lead author of the study:

The impact was remarkable: Mars’s upper atmosphere was flooded by electrons. It was the biggest response to a solar storm we’ve ever seen at Mars. 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. 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.

*ESA’s Swarm satellites map Earth’s magnetic field as it is warped by the solar storm of May 2024. Credit: ESA*

Thanks to Earth’s magnetosphere, the response of the upper atmosphere was less intense, with much of the storm’s particles deflected away from the planet or diverted toward the poles (causing the aurorae). This highlights the differences between our planets and also demonstrates the importance of studying how space weather impacts different bodies in the Solar System. Since solar storms can endanger astronauts and equipment in orbit, as well as disrupt satellites and electrical grids on the surface, space weather forecasting is of vital importance.

This is difficult, however, as the Sun emits solar flares and CMEs unpredictably, making studying them a matter of luck and timing. Fortunately, the team was able to use the new technique just 10 minutes after the solar storm reached Mars. In total, the team captured the aftermath of three solar events that were part of the same storm but differed in the type of material ejected and the way it was done. This included a flare of radiation, a burst of high-energy particles, and a CME. Said Colin:

The results improve our understanding of Mars by revealing how solar storms deposit energy and particles into Mars’s atmosphere – important as we know the planet has lost both huge amounts of water and most of its atmosphere to space, most likely driven by the continual wind of particles streaming out from the Sun. But there’s another side to it: the structure and contents of a planet’s atmosphere influence how radio signals travel through space. 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, making it a key consideration in our mission planning – and impacting our ability to investigate other worlds.

Further Reading: ESA

California and 16 Democratic states are suing to challenge a Trump administration policy requiring higher education institutions, including University of California and California State University campuses, to collect data — including student grade point averages — to prove they don’t illegally consider race in admissions.

Attorney General Rob Bonta is among the state attorneys general who filed the suit Wednesday against a Department of Education rule that asks colleges to submit “the race and sex of colleges’ applicants, admitted students and enrolled students.” Bonta called the requirement a “fishing expedition” that is “demanding unprecedented amounts of data from our colleges and universities under the guise of enforcing civil rights law.”

“This is the same administration, I’ll remind you, that gutted the U.S. Department of Education’s Office of Civil Rights, leaving thousands of civil rights complaints and investigations in limbo,” Bonta said in a statement. “This latest sham demand threatens to turn a reliable tool into a partisan bludgeon. California is committed to following the law — and we’re going to court to make sure the Trump Administration does the same.”

The policy, announced in August, requires schools to submit disaggregated data on gender, race, grade point averages and test scores of applicants, admitted students and enrolled students by March 18.

The Trump administration is requesting seven years of data and says it wants schools to prove they are not illegally considering race as a factor in admissions — a practice the struck down nationally after a 2023 Supreme Court case involving Harvard. In that case, justices said colleges may still consider how race has shaped students’ lives if applicants share that information in their admissions essays.

California and Democratic opponents of the suit, which was filed in a Boston federal court, say in their complaint that the government is attempting to turn the nonpartisan National Center for Education Statistics into a “mechanism for law enforcement and the furthering of partisan policy aims.”

The Trump administration has accused numerous elite institutions, including the UC system, breaking the law by using race in admissions and discriminating against white and Asian American students. This year, it sued UCLA in federal court, alleging that the David Geffen School of Medicine illegally practices affirmative action. UC and UCLA have said they follow California state law, which has banned considering race as a factor in admissions since 1997.

President Trump ordered the new policy last summer after he raised concerns that colleges and universities were using personal statements and other proxies to consider race, which he views as illegal discrimination.

Ellen Keast, an Education Department spokesperson, defended the data collection.

“American taxpayers invest over $100 billion into higher education each year and deserve transparency on how their dollars are being spent,” Keast said in a statement. “The Department’s efforts will expand an existing transparency tool to show how universities are taking race into consideration in admissions. What exactly are State AGs trying to shield universities from?”

The new policy is similar to parts of recent settlement agreements the government negotiated with Brown University and Columbia University, restoring their federal research money. The universities agreed to give the government data on the race, grade-point average and standardized test scores of applicants, admitted students and enrolled students. The schools also agreed to be audited by the government and to release admissions statistics to the public.

The government made a similar ask of UC in August when it proposed a $1.2-billion settlement fine to resolve allegations of federal civil rights law violations at UCLA after cutting off more than half a billion dollars in federal medical, science, and energy research funding.

UC President James B. Milliken said the university will not pay the fine but is open to talks with the Trump administration. No agreement has been reached, although faculty and union-led lawsuits resulted in research funding being restored and strict limits on the Trump administration attempts to reshape UC policies and culture through threats of funding cuts.

The Trump administration’s August memo on race in admissions directs Education Secretary Linda McMahon to require colleges to report more data “to provide adequate transparency into admissions” to the National Center for Education Statistics. After a public comment period — in which California and other Democrat-led states submitted notices opposing the rule — the Department of Education finalized the reporting requirement on Dec. 18.

If colleges fail to submit timely, complete and accurate data, McMahon can take action under Title IV of the Higher Education Act of 1965, which outlines requirements for colleges receiving federal financial aid for students, according to the memo.

Massachusetts Attorney General Andrea Joy Campbell, who co-led the suit along with Bonta, said in a statement that “there is no way for institutions to reasonably deliver accurate data in the federal government’s rushed and arbitrary timeframe, and it is unfair for schools to be threatened with fines, potential losses of funding, and baseless investigations should they not fulfill the administration’s request.”

The government uses the Integrated Postsecondary Education Data System, or IPEDS, to gather information from thousands of colleges and universities that receive federal aid. The coalition also argues that the new data collection demands jeopardize student privacy.

“Many institutions have data protection obligations to their students, which are placed at risk by the administration’s new IPEDS demands for in-depth information about individual students,” the plaintiffs wrote in the lawsuit.

Casey writes for the Associated Press.