A planet 250% the mass of Mars was just found orbiting proxima Centauri the closest solar system to Sol.
The planet likely is tidally locked with a band around the planet in perpetual sunset with livable temperatures. The planet likely has a thick abiotically produced pure oxygen atmosphere.
https://www.newscientist.com/article/2307932-tiny-exoplanet-proxima-d-is-third-spotted-in-nearest-star-system-to-us/