In December 2023, scientists looking at Mars data stumbled across something completely unexpected — observations of an atmospheric effect never before seen in the Red Planet’s atmosphere. Using instruments aboard NASA’s MAVEN (Mars Atmosphere and Volatile Evolution) mission, scientists identified a phenomenon known to occur in Earth’s magnetosphere, where charged particles are squeezed like toothpaste coming out of a tube along magnetic structures called flux tubes. This so-called Zwan-Wolf effect aids in the deflection of solar wind around Earth and has been observed and studied there for decades. Now, a new study published in Nature Communications provides the first comprehensive observations of the same effect in Mars’ atmosphere.

“When investigating the data, I all of a sudden noticed some very interesting wiggles,” said Christopher Fowler, a research assistant professor at West Virginia University in Morgantown and lead author of the study. “I would never have guessed it would be this effect, since it’s never been seen in a planetary atmosphere before.”

The Zwan-Wolf effect was first discovered in 1976, and until now has only been observed in planetary magnetospheres, not their atmospheres. Unlike Earth, Mars is not protected by a global magnetic field, affecting how it interacts with the solar wind and space weather. In this new study, the Zwan-Wolf effect was observed in the ionosphere — deep within the Martian atmosphere below 200 km — which contains significant numbers of electrically charged particles. The data showed that these charged particles were being squeezed and distributed around Mars’ atmosphere.

Although Mars has an induced magnetosphere, a magnetic field generated by the solar wind interacting with the Martian ionosphere, it can greatly change in size and shape with large solar wind and space weather events. That is what Fowler and his team saw in the MAVEN data when a large solar storm hit Mars. Based on their findings, the Zwan-Wolf effect may be occurring constantly in the Martian ionosphere but at levels undetectable by MAVEN’s instrumentation. The impact of the space weather event appears to have amplified the effect, allowing the scientists to observe it in the data.

In the beginning, Fowler and his team came across some interesting-looking fluctuations in measurements of the magnetic field as the spacecraft flew through the atmosphere. To explain this, they dug into observations made by several instruments on MAVEN, including measurements of the charged particle environment in the ionosphere. Their sleuthing uncovered even more weird and interesting features in the data. After ruling out several other possibilities, the team was able to identify the culprit as the Zwan-Wolf effect, which explained all the features they were seeing.

“No one expected that this effect could even occur in the atmosphere,” said Fowler. “That’s what makes this even more exciting. It introduces interesting physics that we haven’t yet explored and a new way the Sun and space weather can change the dynamics in the Martian atmosphere.”

Understanding the Zwan-Wolf effect at Mars will further our understanding of how space weather affects the planet and provides new insight into how this effect might occur at similar unmagnetized bodies, such as Venus and Saturn’s moon Titan. Observations like this also highlight the importance of knowing how large space weather events can lead to changes in the environment at and around the Red Planet and potentially affect assets on or near Mars.

“Knowing how space weather interacts with Mars is essential,” said Shannon Curry, the principal investigator of MAVEN and research scientist at the Laboratory for Atmospheric Space Physics at the University of Colorado Boulder. “The MAVEN team continues making new discoveries with our datasets and finding these links between our host star and the Red Planet.”

The MAVEN spacecraft launched in November 2013 and entered Mars’ orbit in September 2014. The mission’s goal is to explore the planet’s upper atmosphere, ionosphere, and interactions with the Sun and solar wind to explore the loss of the Martian atmosphere to space. Understanding atmospheric loss gives scientists insight into the history of the Red Planet’s atmosphere and climate, liquid water, and planetary habitability. The MAVEN spacecraft, in orbit around Mars, experienced a loss of signal with ground stations on Earth on Dec. 6, 2025. In Feb. 2026, NASA launched an anomaly review board to assess the probable current state of the spacecraft and the likelihood of its recovery.

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 is also 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.  

By Willow Reed
Laboratory for Atmospheric and Space Physics, University of Colorado Boulder

Media contacts:

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Headquarters, Washington
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Sarah Frazier
Goddard Space Flight Center, Greenbelt, Md.
sarah.frazier@nasa.gov