Abstract: A method for generating power and a power supply for use in the atmosphere on Mars that use the Martian atmosphere as a working fluid. The power supply has an open Brayton cycle combined turbocompressor and turbogenerator that use the Martian atmosphere for their operation. The Martian atmosphere working fluid picks up heat derived from a nuclear heat source that transfers the heat to the working fluid by laminar flow heat exchange. The combined turbocompressor and turbogenerator have provisions for separating dust from the dust laden Martian atmosphere and for operating with any residual Martian atmospheric dust that is ingested into the combined turbocompressor and turbogenerator. Reliability of operation is achieved by having two functionally separate power operating units that each have their own combined turbocompressor and turbogenerator and by only using one power unit at a time.