Scientists have observed the Zwan-Wolf effect at Mars for the first time, revealing how even planets without a global magnetic field can exhibit complex magnetic behavior. The effect, caused by solar wind compressing magnetic boundaries, leads to a drop in charged particle density along the planet’s magnetic structures. It was detected during a powerful solar storm in December 2023 by NASA’s MAVEN spacecraft, which recorded a 50% reduction in ionospheric particle density on Mars’s nightside.

The discovery, published in Nature Communications, involved researchers from France, the U.K., and the U.S. They found that the intense magnetic structures generated by the coronal mass ejection allowed the normally undetectable effect to be observed. While the Zwan-Wolf effect is likely always present at Mars, it’s typically too weak for most instruments to measure.

This finding expands our understanding of how solar activity interacts with planetary environments, especially for unmagnetized bodies like Mars. It suggests that magnetic phenomena in space may be more widespread than previously thought, influencing atmospheric loss and space weather on other planets.