On The Effect Of The Obliquity Of Mars To The Hydrogen Escape And The Fate Of Water In The Last Millions Of Years.
G. Gilli, Instituto De Astrofisica De Andalucia (Iaa-Csic), Granada, Spain (Gilli@Iaa.Es), F. Gonzalez-Galindo,
Iaa-Csic, Granada, Spain, F. Forget, J. Naar, E. Millour, Laboratoire De Meteorologie Dynamique (Lmd)-Ipsl,
Paris, France, J-Y. Chaufray, Laboratoire Atmospheres, Observations Spatiales (Latmos)-Ipsl, Paris, France.

Introduction
The Climate Of A Planet Depends On Its Orbital And Rotation
Parameters, And In Particular On The Obliquity (I.E. Inclination Of Its Axis Of Rotation To Its Orbit Plane). While
For The Earth The Oscillations Of Those Parameters Are
Small (± 1.3º For Obliquity), In The Past 250 Myrs Mars’S
Axis Inclination Covered A Large Range Of Variations, Between 0 And 66º, With A Mean Obliquity Of About 35º
[Laskar Et Al., 2004]. Different Orbital Configurations
Induce Significant Modifications In Fundamental Aspects
Of The Martian Climate, Mainly Due To The Differences In
The Distribution Of The Insolation, Such As The Co2 Cycle
(And Thus The Surface Pressure),The Dust And Water Cycle,
Or The Global Circulation [Forget Et Al., 2017]. The North
Pole Insolation Is A Key Parameter Controlling The Stability Of Water Ice Of The Northern Polar Cap. As Shown In
Figure 1 It Could Have Varied Up To 350 W M−2 In The
Past 20 Million Years.