The microwave spectrum and nature of the subsurface of Mars

Abstract

Expected microwave spectra of Mars are computed using an improved thermal model and accurate aspect geometry. It is found that when seasonal polar cap effects are included in the calculations, the observable spectrum of Mars is flat from 0.1-21 cm to within the accuracy of present data. The spectra obtained from this model are consistent with all the data and are obtainable from a relatively simple model (homogeneous, dry, smooth dielectric sphere). This result differs from that predicted by the analytical theory in common use which is in apparent conflict with the observed spectra. A range of electrical loss tangents of 0.003 < tan Δ < 0.015, covering the extreme limits for likely dry particulate geological materials, is employed. The case of a lunar-like subsurface, with tan Δ = 0.0075, is completely consistent with all present data. Final values of other relevant parameters are: thermal inertia = 0.006 cal cm-2deg-1sec-1 2, effective dielectric constant = 2.5, Bond albedo = 0.25, and infrared emissivity = 0.90. © 1972.