Analysis of rocket-borne mass spectrometric thermospheric measurements of major and minor neutral species by coupled multicomponent equations of motion reveals the lower thermosphere to be in a nonequilibrium state. The individual species motion and thermal diffusion are significant factors in (1) the theoretical calculatios of self-consistent species distributions and velocities for almost all atmospheric species and (2) the determination of lower-thermospheric temperatures from individual species profiles. The theoretical approach and the results of rocket probe analyses with regard to thermospheric species distributions, temperatures, and vertical velocities are presented.