The best-known proposal came from Jim Green and colleagues at NASA in 2017: park a powerful dipole magnet at the Mars-Sun L1 point, roughly a million kilometres upstream, and let its field carve a magnetotail that Mars sits inside. Their modelling suggested the shielded planet would warm by several degrees as atmospheric loss halted and CO2 sublimed — an elegant idea that puts one object in one place.
DuPont and Murphy took the physics apart in 2021 and found the compact version is the expensive one. Because the superconducting material required scales as the inverse square of the critical field and the inverse cube of the loop radius, small magnets are punishingly costly: a compact L1 dipole would need mining roughly 10% of Mars itself.
Their counter-intuitive result is that the cheap design is the enormous one. A superconducting loop encircling the entire planet at a radius of about 3,400 kilometres, made of wire roughly 5 centimetres in diameter, would mass around 10⁹ kg and require mining on the order of 10¹⁵ kg — about 0.1% of the volume of Olympus Mons. Against solar system material abundances, that is achievable.
The shield is the long-game entry on this list. Atmospheric loss operates over hundreds of millions of years, so nothing about a base, a dome or even a warmed Mars depends on having one. It matters if the goal is an atmosphere that stays — and it also shields the surface from solar energetic particles, which is a benefit measured in human lifetimes rather than geological ones.
Every other atmospheric intervention fights an ongoing loss to the solar wind. A magnetosphere is the only measure that makes an added atmosphere durable on geological timescales.
DuPont and Murphy show a planet-encircling loop needs about 10⁹ kg of material and 10¹⁵ kg mined — roughly a thousandth of Olympus Mons, well inside solar-system abundances.
Deflecting solar energetic particles cuts one of the two radiation components at the surface, which matters on a human timescale, not just a planetary one.
The Green et al. modelling found that halting atmospheric loss allows CO2 to accumulate and the planet to warm by several degrees with no additional intervention.
A superconducting ring 3,400 km in radius is a structure larger than any megaproject in history, requiring in-situ manufacturing on Mars at industrial scale.
Atmospheric stripping acts over hundreds of millions of years. Nothing about the first century of Mars settlement is limited by the absence of a magnetic field.
The intuitive design — one magnet at L1 — requires mining around 10% of Mars because of how superconductor mass scales with field strength and radius.
A superconducting loop that quenches releases its stored magnetic energy catastrophically, and the shield it provides disappears the instant it does.
| Conductor mass | ~10⁹ kg | Superconducting wire, ⌀ ~5 cm |
| Material mined | ~10¹⁵ kg | ~0.1% of Olympus Mons |
| Geometry | r ≈ 3,400 km | Encircling the planet |
| Cryogenics | Continuous | Superconducting state maintained indefinitely |
Yes, in principle. The most resource-efficient published design is a superconducting loop about 3,400 km in radius encircling the planet, massing roughly 10⁹ kg and requiring about 10¹⁵ kg of mined material.
Jim Green and colleagues proposed a dipole at Mars-Sun L1 in 2017. DuPont and Murphy later showed the compact geometry is the expensive one — it would require mining roughly 10% of Mars — because superconductor mass scales inversely with the cube of the loop radius.
Not on human timescales. Solar-wind stripping operates over hundreds of millions of years. A magnetosphere matters for making an added atmosphere permanent, and for reducing solar-particle radiation at the surface.
