Despite its proximity to its star, the dim red light of TRAPPIST-1 is so faint that TRAPPIST-1 c receives a similar amount of energy to Venus in the Solar System, and like Venus it orbits on the inner edge of the habitable zone. For this reason, it was initially hypothesised that the planet might also be similar to Venus in other ways, perhaps being swathed in thick atmosphere holding the heat received from the star. Further analysis has shown that this is not the case, and if TRAPPIST-1 c has an atmosphere at all, it is lacking in the greenhouse gases needed to trap significant quantities of heat.
The planet'sorbit is so close to its star that it is likely to be tidally locked, permanently showing only one face to TRAPPIST-1 so that, viewed from the surface of the planet, its star would remain fixed in the sky. The planet's close orbit also implies that it will be subject to tidal forces from the star'sgravity, meaning that it is likely to be geologically active.