Interior Temperatures of the Northern Polar Cap on Mars

Icarus, Vol. 144, No. 2, p. 456-462, 2000 

J. Larsen and D. Dahl-Jensen
Departement of Geophysics, The Niels Bohr Institute of Astronomy, Physics and Geophysics, University of Copenhagen.

ABSTRACT.
Knowledge about the interior temperatures of the polar caps on Mars is crucial for the understanding of stratigraphy and dynamics of the polar caps. The insolation and thereby the temperatures of the surface are strongly influenced by factors including obliquity, conductivity, and albedo. Basal temperatures are mainly determined by surface temperature, cap thickness, thermal conductivity, and aerothermal (Aero, Greek for Mars) heat flux. This paper presents a model for the northern polar cap on Mars, where temperature profiles are determined as a function of orbital parameters (obliquity and eccentricity), thermal conductivity, aerothermal heat flux, and cap thickness. Furthermore we will look at the thermal behavior of the upper layer (~100 m) of a martian ice cap. There is strong evidence that the northern polar cap consists mainly of H₂O ice. In the model we will treat the cap as that of H₂O ice with a high dust content and the possibility for solid CO₂ or CO₂ clathrates. The temperature model shows that the ice is most likely flowing and that the flow rate oscillates with a time lag of 30-70 Kyrs compared to the surface temperature obliquity oscillation. The possibility for measuring the aerothermal heat flux by measuring the temperature in the upper 2 m of the ice cap is not very good, but measurements of temperatures through the top 2 m of the ice could provide valuable information on the conductivity of the ice and thereby the constituents of the Mars ice cap.