Mars glows with auroras of its own, and scientists have long wondered how a planet without a global magnetic field manages to produce them. New analysis of data from a long-running NASA orbiter suggests the Red Planet assembles at least some of those light shows using the very same physics that lights up the skies over Earth’s poles, only shrunken down to a fraction of the scale.
The Dungey cycle, running in miniature
On Earth, auroras are powered by a process known as the Dungey cycle. The planet’s magnetic field connects with the magnetic field carried by the solar wind, then stretches, snaps and reconnects on the night side, flinging charged particles down into the upper atmosphere where they collide with gas and make it glow. The surprise at Mars is that the same engine appears to be at work despite the planet lacking the vast, planet-wide magnetic field that engine was assumed to require. Instead of one global field, Mars carries scattered patches of magnetism locked into ancient crustal rock, and those patches turn out to be enough to run the cycle locally.
The finding reframes the Martian aurora not as an exotic oddity but as a smaller relative of a familiar terrestrial phenomenon, driven by the same fundamental interaction between a magnetic field and the stream of particles from the Sun.
What MAVEN measured above the crustal fields
The result rests on observations from the Mars Atmosphere and Volatile Evolution orbiter, which spent more than a decade circling the planet and sampling its upper atmosphere and surrounding space environment. By watching where ultraviolet auroral emissions appeared and correlating them with the local magnetic conditions, researchers traced the glow to spots where crustal magnetic fields reconnect with the solar wind’s magnetic field. That reconnection opens a path for charged particles to funnel down into the atmosphere, producing the emissions the spacecraft detected. NASA described the mechanism and its significance in its MAVEN mission release.
Because the Martian fields are patchy rather than global, the auroras they generate are localized, flickering above particular regions of the southern highlands where the buried magnetism is strongest.
Why a global magnet was thought necessary
The discovery is notable precisely because it overturns an assumption. The circulation of energy through the Dungey cycle was believed to demand a large, coherent magnetosphere, the kind Earth possesses and Mars lost long ago. Mars once had a global field, but it faded billions of years ago, leaving the atmosphere exposed to erosion by the solar wind. That history is a central reason the planet is cold and dry today. Finding that the same energy-circulating process still operates over remnant magnetic patches shows the mechanism is more flexible than expected, as an independent account from phys.org describing the miniature magnetic engine laid out.
A mission that keeps delivering after its end
What makes the timing striking is that the spacecraft behind the result is no longer operating. Controllers lost contact with the orbiter in December 2025, and the mission was formally declared over on June 3, 2026. Yet the archive it built over years of observation remains a rich resource, and this aurora analysis draws entirely on that stored data. It is a reminder that planetary missions often produce some of their most important science well after the hardware falls silent, as researchers keep mining measurements that no active instrument is still collecting.
That long tail of discovery is one argument for the patient, multiyear observing campaigns that orbiters make possible, since the value of the data does not expire when the mission does.
What the comparison teaches about both planets
Understanding Martian auroras is not just a curiosity. The same interactions that light the sky also govern how the solar wind strips gas from the top of the atmosphere, a process that helped transform Mars from a potentially wetter, warmer world into the desert it is now. Watching the physics play out on a planet with only fragments of a magnetic field gives scientists a natural experiment, a way to isolate how magnetism, or the lack of it, shapes a planet’s exposure to its star.
By showing that Earth and Mars share a common auroral engine despite their very different magnetic histories, the work ties two seemingly separate stories together and sharpens the picture of how planets respond to the constant pressure of the solar wind.
Fragments of an ancient magnetic past
The crustal magnetic patches that make these auroras possible are themselves relics of a vanished era. Billions of years ago the planet is thought to have generated a global magnetic field from a churning molten core, much as Earth still does. When that internal dynamo shut down, the planet-wide field disappeared, but pockets of magnetism stayed frozen into rocks that had cooled while the field was active. Those preserved patches, concentrated in the southern highlands, are the strongest surviving traces of a magnetic history that otherwise ended long ago.
Finding that such fragments can still run a version of the auroral engine gives scientists a rare, tangible link to that distant chapter. The location and strength of the auroras effectively map where the old magnetism remains, offering clues about the planet’s geological evolution and the timing of its dynamo’s collapse. It also reshapes expectations for other worlds, suggesting that even a body without a global field might display auroras wherever remnant magnetism survives, a possibility that widens the range of places where the phenomenon could appear. Rather than a curiosity confined to one planet, the interaction begins to look like a widespread outcome of magnetism meeting the solar wind.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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