Astronomers using the Spitzer Space Telescope discovered that exoplanet LHS 3844b probably lacks any atmosphere at all. (Credit: ESO/NASA)

Rocky planets just a little larger than Earth are some of the best targets for finding life in our local cosmic neighborhood. They’re abundant. But it’s not just the size that has to match Earth. Our planet wouldn’t be the life-sheltering place it is without its atmosphere, which keeps us warm enough not to freeze, but not so hot that we smother or boil a