Mass fractionation in hydrodynamic escape

In mass fractionation during the hydrodynamic escape of gases from an inner planet's atmosphere, the readier escape of light gases generates a linear or concave downward line in a plotting of the log of remaining inventory against atomic mass. Just as such an episode of hydrodynamic escape during Mars' early history could have led to the mass-dependent depletion of the noble gases that has been noted in the Martian atmosphere, in the event that the Martian atmosphere was initially hydrogen-rich, an early earth-history episode may have resulted in a mass-dependent fractionation of the xenon isotopes.