An atom carries kinetic energy by its movement speed. It carries thermal energy by the internal oscillation frequency of body parts.

The empty space contains no matter, no particle, no solar wind, no photon, no field, no force, no energy, no property, nothing at all. Otherwise, no planets can have a stable orbit due to orbital drag. Low orbit satellites such as the ISS must use propellant to periodically loft the station to a higher orbit.

If there is any matter in empty space, moving stars and planets will be slowing down by time.