Artist's impression of a habitable Mars. Image: NASA Goddard Space Flight Center
Could humans give Mars a protective magnetic field? A 2021 paper by Ruth Bamford and colleagues argues that it may be possible in principle, by building a ring of electrically charged particles around the planet that would act a little like Earth's own magnetic shield. The paper, titled "How to create an artificial magnetosphere for Mars", is an engineering study of options, not a plan that anyone is building, and a magnetic shield on its own would still be far from making Mars a place where people could breathe outdoors.
Here is what the proposal says, why a magnetic field matters for Mars, and what stands between the idea and reality.
Why Mars lost its shield
Earth is wrapped in a global magnetic field generated by the churning of molten iron in its outer core. That field deflects much of the solar wind, the stream of charged particles flowing constantly from the Sun, and helps protect the atmosphere and life at the surface.
Mars once had a global field too. Magnetised rocks in its ancient crust record it. But the planet's internal dynamo shut down roughly four billion years ago. Mars is smaller than Earth, so its interior cooled faster, and without that churning core the global field faded. Patches of magnetised crust remain, but there is no planet-wide shield today.
Without that protection, the solar wind interacts directly with the upper atmosphere and slowly strips gas away into space. Spacecraft such as Mars Express and NASA's MAVEN orbiter have watched charged particles streaming off the planet. Today the Martian atmosphere is about 96 per cent carbon dioxide, and its average surface pressure is only around 0.6 per cent of Earth's at sea level.
What the 2021 paper proposes
The paper was written by Ruth Bamford of the Rutherford Appleton Laboratory with co-authors including Barry Kellett, James Green, Chuanfei Dong, Vladimir Airapetian and Bob Bingham. It was accepted by the journal Acta Astronautica and posted on the arXiv preprint server in November 2021. (Older reports credited the paper to Cornell University, but Cornell simply runs arXiv, which hosts research from all over the world.)
The authors compare different ways of creating an artificial magnetic field that could surround the whole planet, looking at where the hardware would go, how it would be assembled and how much power and mass each option needs. Their preferred concept is a ring of charged particles, similar to a radiation belt, circling Mars.
The particles would come from material ejected from one of Mars's moons. Phobos, the larger and closer moon, is the moon most reports have discussed, though the paper's summary refers only to "one of the moons of Mars." The authors compare the idea with a natural example: Jupiter's volcanic moon Io feeds a doughnut-shaped cloud of charged gas, the Io plasma torus, around its planet. Around Mars, electromagnetic and plasma waves would be used to drive a current through the ring, and that current would generate a magnetic field large enough to envelop the planet.
The authors say this approach had the lowest power, assembly and mass requirements of the options they considered. They also suggest that the same principles might one day protect smaller targets, such as spacecraft, space stations or bases on the Moon.
Why a shield alone would not make Mars habitable
It is tempting to read headlines about "terraforming Mars" and imagine green fields under a blue sky. The reality is much more modest.
- The atmosphere is far too thin. Stopping further losses does not add air. Mars would still need a vastly thicker atmosphere to allow liquid water on the surface and to let people go outside without pressure suits.
- There may not be enough gas to release. A NASA-sponsored study led by Bruce Jakosky and published in Nature Astronomy in 2018 concluded that Mars does not hold enough accessible carbon dioxide to warm and thicken its atmosphere significantly. In Jakosky's words, terraforming is "not possible using present-day technology."
- Breathable air is a separate problem. Even a thicker atmosphere would be mostly carbon dioxide. Producing oxygen on a planetary scale is an entirely different challenge from blocking the solar wind.
- Atmospheric loss is slow. Mars took billions of years to reach its current state. A magnetic field would matter most for a future atmosphere that people had already managed to build.
Where an artificial magnetosphere could help sooner is radiation. Charged particles from the Sun are a health concern for astronauts, and a local magnetic shield around a base or spacecraft is one of several protection ideas researchers continue to study.
Common myths about Mars and magnetic fields
- "Mars has no magnetic field at all." Not quite. It lacks a global field, but parts of its crust are strongly magnetised, and the interaction between the solar wind and the upper atmosphere creates a weaker induced field.
- "Electrolysing Martian ice would quickly give Mars an Earth-like atmosphere." Splitting water releases oxygen and hydrogen, which can supply a base, but it would not come close to supplying a whole planet's atmosphere on any human timescale.
- "Scientists plan to build this." The paper is a feasibility study comparing concepts. No agency has announced a mission to create a Martian magnetosphere.
What missions are learning now
Before anyone could design a shield, scientists need to understand exactly how Mars loses its atmosphere today. NASA's MAVEN spacecraft has been studying that process since 2014. In November 2025 NASA launched ESCAPADE, a pair of small spacecraft built at the University of California, Berkeley's Space Sciences Laboratory, on Blue Origin's New Glenn rocket. Due to arrive at Mars in 2027, the twin probes are designed to give a stereo view of the planet's magnetic environment and show how energy from the solar wind drives atmospheric escape.
Data like this will help researchers judge whether ideas like Bamford's are worth pursuing, and how large and powerful any artificial shield would need to be. For now, the artificial magnetosphere remains a thought-provoking piece of long-term engineering thinking: a useful way to make a science-fiction idea specific enough to test against real numbers.
Sources: Bamford et al., How to create an artificial magnetosphere for Mars (arXiv / Acta Astronautica); Wikipedia: Magnetosphere of Mars; Northern Arizona University: the 2018 NASA-sponsored terraforming study; UC Berkeley Space Sciences Laboratory: ESCAPADE. Story first reported by ScienceAlert. Image: NASA Goddard Space Flight Center.
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