Could super-Earths or mini-Neptunes host life among the stars?

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By DANIEL CLERY, Science. 

Excerpt: Living on one of the seven Earth-size planets in the TRAPPIST-1 system would be strange.... Looming ominously in the sky is an enormous red star, prone to fiery outbursts and appearing several times bigger than the Sun. Hours of the day don’t exist; each planet is tidally locked to the star so that one side is forever scorchingly hot, the other eternally frozen. Along the margin dividing the day- and nightsides—the only place with a tolerable climate—a ceaseless wind blows and the star hangs on the horizon, in perpetual sunset. A short stroll into the dark side brings your planetary companions into view. Every few days one or more passes overhead like a floating lantern, larger than the Moon. ...the quest to learn whether one of the TRAPPIST-1 planets could make a comfortable home for our imaginary observer has been an exercise in frustration. When the seven known planets around TRAPPIST-1 were revealed in 2017, they were ...the best place to look for a habitable planet with JWST, NASA’s 2-year-old orbiting observatory. ...JWST’s ability to peer into exoplanets’ atmospheres in the infrared, where life-friendly molecules such as water and carbon dioxide leave their fingerprints, is unique. ...four of the seven are reckoned to sit in a habitable zone where liquid water could exist on their surfaces. ...transits are a boon to observers, because if there is an atmosphere, some of the starlight will pass through it...selectively absorb the light at specific wavelengths, creating troughs in the starlight’s spectrum. Astronomers have used the technique to find evidence for carbon dioxide, methane, and water in the atmospheres of large, hot, uninhabitable planets. ...By the end of its third year, JWST will have lavished 175 hours of observing time on TRAPPIST-1. However, JWST has yet to find any firm evidence of an atmosphere around TRAPPIST-1’s planets.... 

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