The four planets orbiting Barnard's star are being sandblasted into oblivion. A team of 38 researchers, led by David Brain of the University of Colorado Boulder, has published a model of atmospheric escape around Barnard's star — the closest single star to Earth at 6 light-years, and an ancient,...
image from GPT Image 1.5
Modeling atmospheric escape from Barnard's star (the closest single star to Earth at 6 light-years) reveals that even this ancient, magnetically quiet M-dwarf would strip a Mars-like atmosphere in ~350,000 years and an Earth-like atmosphere in ~50 million years. Since Barnard's star is 7-10 billion years old—making it the gentlest possible case for atmospheric retention due to its low activity level—younger M-dwarfs would experience even faster atmospheric loss. The primary driver is thermal escape driven by XUV radiation, which elevates atmospheric escape rates 2-5 orders of magnitude above present-day Mars.
The four planets orbiting Barnard's star are being sandblasted into oblivion.
A team of 38 researchers, led by David Brain of the University of Colorado Boulder, has published a model of atmospheric escape around Barnard's star — the closest single star to Earth at 6 light-years, and an ancient, quiet M-dwarf that should represent the gentlest possible case for planet atmosphere retention. The result, posted to the preprint server arXiv on March 12, 2026 and submitted to The Astrophysical Journal arXiv:2603.11561: even here, a Mars-like atmosphere would be stripped in roughly 350,000 years. An Earth-like atmosphere would last about 50 million years. Neither is long enough to matter for the development of surface life.
"By extension, Mars-like planets orbiting any M dwarf near the habitable zone should not retain atmospheres for extended periods of time," the paper concludes. That word "extension" carries some weight — Barnard's star is 7 to 10 billion years old, making it roughly twice the age of the Sun. Younger M-dwarfs, which are more magnetically active and produce more radiation and stellar wind, would strip atmospheres faster. Barnard's is the easiest case. The result is not encouraging.
The four planets — confirmed last year by a team led by Jonantti Basant and colleagues using the ESPRESSO spectrograph at Chile's Very Large Telescope — are all small, ranging from 19 to 34 percent of Earth's mass, and orbit at periods of 2.34, 3.15, 4.12, and 6.74 days. All four orbit interior to Barnard's star's habitable zone, which begins at roughly 10 days; their periods are all shorter than that inner edge, placing them closer to the star than where the habitable zone begins. None of them are habitable candidates by orbital period alone.
Barnard's star is an M-type red dwarf, the most common stellar class in the galaxy, with a mass roughly 14 percent of the Sun's. It was discovered in 1916 by American astronomer Edward Emerson Barnard — one of those historical footnotes that makes the sky feel more populated than you'd think. The star's age and low activity level made it a natural choice for this kind of modeling: if atmospheric loss is going to be manageable anywhere around an M-dwarf, it should be manageable here.
It is not.
The team's modeled planet — placed at 0.087 astronomical units from Barnard's star to receive the same total flux that Mars receives from the Sun — experiences escape rates dominated by thermal processes, elevated 2 to 5 orders of magnitude above present-day Mars. The primary driver is XUV radiation — high-energy X-ray and extreme ultraviolet photons that heat the upper atmosphere and drive a thermal wind off the planet. Add in the stellar wind, and you're not slowly boiling so much as sandblasting with hot air.
The paper does not model the actual Barnard's planets directly. It models a Mars-analog at Mars-equivalent flux. But the conclusion is hard to escape: if a Mars-like planet at Barnard's would lose its air in a few hundred thousand years, the four confirmed planets — which orbit closer in than the modeled case — would not retain atmospheres significantly longer. The planets likely formed farther from the star and migrated inward through interactions with the protoplanetary disk, which means they may have started with more atmosphere than they currently have. They did not keep it.
This is not a story about four specific planets being dead. It is a story about a category problem in the search for habitable worlds.
M-dwarfs are the obvious place to look for habitable planets: they are the most common stars, they are long-lived — potentially for trillions of years, far outlasting the Sun — and they are easy to survey because a planet passing in front of a small star produces a larger relative signal. The James Webb Space Telescope has been targeting them. Several next-generation ground-based telescopes are designed around M-dwarf atmospheric characterization. A significant fraction of exoplanet science literature, and a non-trivial amount of private capital, is built on the assumption that habitable-zone M-dwarf planets are live targets.
The habitable zone calculation, taken alone, does not account for atmospheric escape. Those are separate problems — one is thermodynamics, one is stellar physics — and the paper suggests they cannot be separated. A planet can receive the right amount of energy for liquid water and still have no atmosphere. The two conditions are not as compatible as the name "habitable zone" implies.
Brain chairs the science advisory board for NASA's MAVEN mission, the Mars Atmosphere and Volatile Evolution spacecraft that has spent the last decade measuring how Mars is losing its own atmosphere today. That provenance matters: this is not a modeling exercise without a real-world anchor. MAVEN data informs the escape rates used in the Barnard's simulations. The team knows what they are looking at because we have a reference case — an actual planet losing its air in real time — and the numbers are not subtle. Two to five orders of magnitude faster than present-day Mars is a large range, but even the low end is catastrophic on geological timescales.
Whether any of this can be circumvented — by stronger magnetic fields, different atmospheric compositions, outgassing rates that replenish faster than escape — is not answered here. The paper establishes a boundary condition, not a final verdict. But a boundary condition is not nothing. It means the problem is harder than the habitability literature has generally assumed, and that the observational bar for "promising M-dwarf planet" is higher than a flux calculation alone would suggest.
The four Barnard's planets sit at orbital periods between 2.34 and 6.74 days. The star's habitable zone, by contrast, spans orbital periods of 10 to 42 days — a range where no confirmed planet exists. The zone, in other words, is empty around the closest single star to Earth. That is probably not a coincidence.
Story entered the newsroom
Research completed — 8 sources registered. Brain et al. (38 authors, submitted to ApJ March 12 2026) modeled a Mars-like planet at 0.087 AU from Barnards star: escape rates 2-5 orders of magnit
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Headline selected: David Brain: M-Dwarf Atmospheres Can't Survive
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