NASA MAVEN (Mars Atmosphere and Volatile Evolution) mission scientists have uncovered a key puzzle piece in understanding certain types of auroras on Mars, finding that they form in a similar way to Earth-based auroras.
Results published Thursday in Nature Communications show the same mechanism that circulates and catapults charged particles into Earth's atmosphere is happening at Mars on much smaller scales because of differences in the two planets' magnetic fields.
The MAVEN spacecraft, in orbit around Mars, experienced a loss of signal with ground stations on Earth on Dec. 6, 2025. On June 3, NASA declared the mission had concluded after finding the spacecraft to be unrecoverable. However, data from the mission is still being used to inform NASA science and future missions to Mars.
When the Sun's magnetic field lines get close to Earth's magnetosphere, the large magnetic bubble protecting the planet, they can reconnect and inject energy and mass throughout Earth's magnetosphere and magnetotail, ultimately firing electrons back into the atmosphere to generate Earth's auroras. This process, called the Dungey cycle, drives electrical currents, accelerates charged particles that create auroras, and controls the circulation of plasma in Earth's magnetosphere and ionosphere.
This new study shows that a miniature version of the Dungey cycle is happening over Mars' strong crustal magnetic fields, which gives scientists a better look into the physics of Martian auroras.
"We knew that magnetic reconnection was happening at Mars but did not expect it to be like the Dungey cycle," said Shaosui Xu, lead author of the study and associate research physicist at the Space Sciences Laboratory at the University of California, Berkeley.
Mars does not have a global magnetic field like Earth. Earth's magnetic field is created by our planet's churning core, while Mars has numerous miniature magnetospheres that arise from intensely magnetized crust scattered around the planet. These regions were formed around 4 billion years ago when lava cooled in the presence of Mars' ancient global magnetic field, which has since disappeared due to intense solar wind stripping the planet's atmosphere.
The MAVEN mission has observed highly localized auroras over these crustal fields, similar to Earth's auroras at the poles, but it wasn't until now that scientists could fully understand the physics of how they form. The study used several instruments aboard the MAVEN spacecraft to build up a picture of the Dungey-like behavior: the Magnetometer and Solar Wind Electron Analyzer instruments, which were used to determine the magnetic configuration and derive electrical currents, and the STATIC (Suprathermal and Thermal Ion Composition) instrument, which was used to measure plasma flows in the ionosphere.
"We really pushed the limit of STATIC to get the data we needed," said Xu. "It was the final piece to the puzzle in understanding these localized auroras."
The realization that a Dungey-like cycle was happening within these crustal magnetic fields answered the question of how the electrons were being energized to create the auroras. It also shows that a Dungey-like mechanism can happen on both large and small scales, giving more insight into where in the solar system this process could be taking place.
"This is a remarkable result that changes how we think of Martian auroras and is another important step toward understanding why Mars and Earth have evolved so differently despite being governed by the same underlying physics." said Shannon Curry, MAVEN's principal investigator and a research scientist at the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder. "I am incredibly proud of our team's work on this discovery and excited to uncover new insights into the Red Planet and its evolution."
By finding out more about this process, scientists also are gaining a better understanding of how the solar environment interacts with the Red Planet as a whole, which is essential for future robotic and crewed missions.
"I remember in graduate school discussing with my advisor how the cycling of crustal magnetic fields could work at Mars," said Xu. "It's incredible to be part of the team that found the answer to that question."
The MAVEN mission is part of NASA's Mars Exploration Program portfolio. The mission's principal investigator is based at the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder, which also is responsible for managing science operations and public outreach and communications. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the MAVEN mission. Lockheed Martin Space built the spacecraft and is responsible for mission operations. NASA's Jet Propulsion Laboratory in Southern California provides navigation and Deep Space Network support.
