Photochemical Escape Of O And C From Mars: The Impact Of Collisional Cross
Sections
M. Gacesa, Space And Planetary Science Center And Department Of Physics, Khalifa University, Abu Dhabi,
Uae (Marko.Gacesa@Ku.Ac.Ae), Y. Lee, University Of Maryland Baltimore County, Md, Usa; Center For Research And Exploration In Space Science And Technology Ii, Md, Usa; Nasa Goddard Space Flight Center,
Planetary Environments Laboratory, Md, Usa, B. M. Krishna, Department Of Physics, Khalifa University,
Abu Dhabi, Uae

Introduction:
Recent Estimates Based On Ar Isotope Fractionation In The Upper Atmosphere Suggest That Mars Has
Lost At Least 66% Of Its Original Atmosphere To Space,
Including Most Of Its Initial Water Inventory. In The
Current Epoch, The Photochemical Escape Is Considered Responsible For Much Of The Loss Of Atomic Oxygen And Carbon, While Jeans Escape Remains The Dominant Escape Mechanism Of Hydrogen. The Classical
Picture Is That H And O Escape From Mars In 2:1 Ratio
When Averaged Over Time Periods Longer Than About
105 Years, With H Escape Responding To O Loss. Thus,
The Physical Processes Governing The O Escape Effectively Determine The Overall Escape Rate, While The
Variations Due To Seasonal Effects And Climate Cycles
Average Out.
More Recently, Nasa’S Mars Atmosphere And
Volatile Evolution (Maven) Mission Detected Seasonal Variations Of Hydrogen Escape In Excess Of An