Mars Has No Magnetosphere. It's Doing the Magnetosphere Thing Anyway.

NASA's MAVEN spacecraft detected strange wiggles in Mars' atmosphere after a powerful coronal mass ejection smashed into the Red Planet in 2023. Those wiggles turned out to be something that, by all existing theory, could not be there.

Identified on Earth in 1976, the Zwan-Wolf effect centers on flux tubes, elongated magnetic structures that channel and compress charged particles the way pressure on a tube forces out toothpaste. Experts long assumed the Zwan-Wolf effect could not happen on Mars because its core has long since solidified and generates no proper magnetosphere. No magnetosphere, no flux tubes. No flux tubes, no toothpaste. Straightforward enough, apparently right up until it wasn't.

A powerful solar storm struck Mars in December 2023, and roughly 12 hours after impact, MAVEN recorded unusual fluctuations in the upper atmosphere. Analysis showed charged particles being funneled and squeezed along temporary magnetic structures created during the storm, in a way that closely matched the Zwan-Wolf effect seen around Earth. Lead researcher Christopher Fowler said the finding caught him completely off guard, since this particular effect had never before turned up in any planet's atmosphere. Until now, it had been observed only in planetary magnetospheres, not atmospheres.

Unlike Earth, where the Zwan-Wolf effect occurs tens of thousands of miles above the surface, the Martian version occurs in the ionosphere at around 125 miles (200 kilometers) altitude. Where the effect typically helps deflect solar wind at Earth, at Mars it squeezes the atmosphere instead, with implications for how space weather interacts with unmagnetized planets.

A study published in Nature Communications provides the first comprehensive observations of this effect in Mars' atmosphere. What it means for our models of unmagnetized planets, and for any future inhabitants of the surface below, remains an open question.

Mars spent four billion years not having a magnetic field. It has apparently been improvising.

Read the full story at Live Science, May 29, 2026

Hot Take: The lead author of a peer-reviewed Nature Communications paper essentially admitting he never saw this coming is doing a great deal of quiet work here. Planetary scientists have been confidently explaining why this effect was impossible on Mars for fifty years, and what's being reported, with admirable restraint, is that Mars was not consulted.