The solar wind and ultraviolet constantly peel a thin layer of gases off Earth, like wind carrying away steam over a hot pot. This process is slow, taking billions of years. But for planets near red dwarfs, it's harsher: they bask right next to the star, and X-ray fluxes sandblast their atmospheres like an abrasive blaster.
Some researchers are convinced that after such bombardment, planets lose all their air and become lifeless. Others remind us that the gas reserves in the interior are unknown — if they are large, the planet can survive the storm, like a tree with deep roots.
The study compares gas losses for planets in the solar system and for worlds around different stars. The conclusion: an atmosphere's fate depends not only on the star, but also on how much gas the planet had from the start. Now we just need to measure it.
Earth loses about 3 kilograms of hydrogen per second — over a year that adds up to 100,000 tons, but it's a drop in the bucket compared to the mass of the atmosphere.
In the movie Interstellar, the heroes search for habitable planets around a supermassive black hole, but real candidates are more often found orbiting red dwarfs, and there, the air might be missing.