"TRAPPIST-1 c likely has an incredibly thin atmosphere, or no atmosphere at all."
My note. The exoplanet.eu site updated various properties for this exoplanet now.
http://exoplanet.eu/catalog/trappist-1_c/
Another site reported on TRAPPIST-1 c too.
https://phys.org/news/2023-06-webb-thick-carbon-dioxide-atmosphere.html
My observation. This looks important concerning TRAPPIST-1, 7 exoplanet system in the phys.org report. “The absence of a thick atmosphere suggests that the planet may have formed with relatively little water. If the cooler, more temperate TRAPPIST-1 planets formed under similar conditions, they too may have started with little of the water and other components necessary to make a planet habitable."
Ref - No thick carbon dioxide atmosphere on the rocky exoplanet TRAPPIST-1 c,
https://www.nature.com/articles/s41586-023-06232-z, 19-June-2023. "...A Venus-analogue atmosphere with sulfuric acid clouds is also disfavoured at 2.6σ confidence. Thinner atmospheres or bare-rock surfaces are consistent with our measured planet-to-star flux ratio. The absence of a thick, CO2-rich atmosphere on TRAPPIST-1 c suggests a relatively volatile-poor formation history, with less than 9.5+7.5−2.3 Earth oceans of water. If all planets in the system formed in the same way, this would indicate a limited reservoir of volatiles for the potentially habitable planets in the system."
I keep seeing periodic references now to Venus like or Venus type exoplanets, the space.com article pointed this out about TRAPPIST-1 c too. "Initially, astronomers thought TRAPPIST-1 c might have a thick carbon dioxide atmosphere like Venus, given it is about the same size and receives a similar amount of radiation from its host star as Venus gets from the sun."
Apparently evolutionary modeling for these exoplanets and confirming atmospheres remains challenging. Here is another possible Venus analog but likely very different too.
Exoplanet may reveal secrets about the edge of habitability,
https://phys.org/news/2023-06-exoplanet-reveal-secrets-edge-habitability.html
"Super-Earth" LP 890-9c (also named SPECULOOS-2c) is providing important insights about conditions at the inner edge of a star's habitable zone and why Earth and Venus developed so differently, according to new research led by Lisa Kaltenegger, associate professor of astronomy at Cornell University. Her team found LP 890-9c, which orbits close to the inner edge of its solar system's habitable zone, would look vastly different depending on whether it still had warm oceans, a steam atmosphere, or if it had lost its water—assuming it once had oceans like Earth's. "Looking at this planet will tell us what's happening on this inner edge of the habitable zone—how long a rocky planet can maintain habitability when it starts to get hot," Kaltenegger said. "It will teach us something fundamental about how rocky planets evolve with increasing starlight, and about what will one day happen to us and Earth."
Concerning the space.com report on TRAPPIST-1 c: "New data from NASA's James Webb Space Telescope (JWST) shows that the atmosphere of a rocky exoplanet in the TRAPPIST-1 system is either non-existent or incredibly thin, making it unfavorable for hosting life as we know it."
It seems as more studies and investigations are done, many exoplanets appear hostile to life, life as we see here on Earth.