Hot H Escape At Mars: An Assessment Of The Importance Of
Photochemical H Loss Mechanisms
B. S. Gregory1, M. S. Chaffin1, R. D. Elliott1, H. Gröller2, J. Deighan1, E. M. Cangi1, 1laboratory For
Atmospheric And Space Physics, University Of Colorado Boulder, Usa (Bethan.Gregory@Lasp.Colorado.Edu),
2
Lunar And Planetary Laboratory, University Of Arizona, Usa.

Introduction:
The Loss Of Hydrogen To Space Has Played An
Important Role In The Desiccation Of Mars, Which Has
Lost Most Of Its Initial Water. Hydrogen Escape Is
Therefore Important For Understanding The Planet’S
Atmospheric Evolution. This Process Has Been Largely
Attributed To Thermal Escape, In Which The High-Energy
Tail Of H Atoms In A Maxwell-Bolzmann Velocity
Distribution May Have Sufficient Energy To Be
Irreversibly Removed From The Upper Atmosphere.
However, A Smaller Population Of Higher-Temperature
H Atoms Is Also Expected To Be Present, Indicated By
Modelling Studies (E.G. Nagy Et Al., 1990) And Inferred