NASA's MAVEN reveals Dungey cycle drives auroras on Mars

NASA scientists have discovered that a process similar to the one that creates auroras on Earth also generates certain types of auroras on Mars, but on a much smaller scale. The finding, published in Nature Communications, reveals that a miniature version of the Dungey cycle—a mechanism involving magnetic reconnection that energizes charged particles—occurs over Mars' strong crustal magnetic fields. This process was previously known to drive Earth's auroras, but its role on Mars had not been fully understood until now.

The discovery affects our understanding of Mars' atmosphere and its interaction with the solar wind. Unlike Earth, which has a global magnetic field generated by its core, Mars has localized magnetic fields in its crust, remnants of an ancient global field that disappeared billions of years ago. These crustal fields create small magnetospheres where the Dungey-like cycle can occur, firing electrons into the atmosphere to produce auroras. The study used data from NASA's MAVEN spacecraft, which orbited Mars from 2014 until its mission concluded in June 2025 after a loss of signal in December 2024.

This finding matters because it explains how electrons are energized to create Martian auroras, a question that had puzzled scientists. It also demonstrates that the Dungey cycle can operate on both large and small scales, suggesting it may occur elsewhere in the solar system. Understanding this process helps scientists learn how the solar environment affects Mars, which is crucial for planning future robotic and crewed missions to the Red Planet.

The study was led by Shaosui Xu of the University of California, Berkeley, who noted that the final piece of the puzzle came from data from MAVEN's STATIC instrument, which measured plasma flows. The research also used the Magnetometer and Solar Wind Electron Analyzer to determine magnetic configurations and electrical currents. The MAVEN mission, part of NASA's Mars Exploration Program, is managed by the Goddard Space Flight Center, with the principal investigator at the University of Colorado Boulder.

Next steps include further analysis of MAVEN's data to uncover more insights into Mars' evolution and its differences from Earth. The findings also inform future missions by improving predictions of how solar storms affect the Martian atmosphere.