The Lateral Continuity and Vertical Arrangement of Dust Layers in the Martian North Polar Cap From SHARAD Multiband Data.

Abstract

Interpretation of radar sounder reflections to infer the structure and composition of the martian polar caps depends on whether bright returns correspond to single packed dust layers or a more finely layered structure. Reflections from multiple layers can create strong resonant scattering (interference) effects that impact analyses of radargram reflectors and inference of dielectric contrast. We identify resonant behavior for an areally extensive reflector in the north polar layered deposits from Shallow Radar data processed in two frequency bands. Echo strength varies by ∼2 dB between subband reflections across a region ∼400 km in extent, with the stronger echo shifting abruptly from the high‐ to low‐frequency band outside the central region of Gemina Lingula. This behavior can arise from resonant scattering between two layers of dust (0.3–0.6 m thick) separated by 0.5–3 m of ice. Such layering requires there be little postdepositional aeolian activity to preserve layer thickness and spacing.