TRAPPIST-1d has a semi-major axis of and an orbital period of 4.05 Earth days. It is more massive but less dense than Mars. Based on fluid dynamical arguments, TRAPPIST-1d is expected to have weak temperature gradients on its surface if it is tidally locked, and may have significantly different stratospheric dynamics than Earth. Based on numerous climate models, the planet may or may not have been desiccated by TRAPPIST-1's stellar wind and radiation; if confirmed, density estimates of the planet indicate it is not dense enough to consist solely of rock. The current state of TRAPPIST-1d depends on its rotation and climatic factors like cloud feedbacks; it is close to the inner edge of the habitable zone, but the existence of liquid water or a runaway greenhouse effect that would render it uninhabitable is dependent on detailed atmospheric conditions. Water could persist in specific settings on the planet.
