1. Astronomie et Systèmes Dynamiques, IMC-CNRS UMR8028, 77 Av. Denfert-Rochereau, 75014 Paris, France
2. Department of Geological Sciences, Brown University, Providence, Rhode Island 02912, USA

Correspondence to: Jacques Laskar¹ Correspondence and requests for materials should be addressed to J.L. (e-mail: Email: laskar@bdl.fr).

Abstract

Since the first images of polar regions on Mars revealed alternating bright and dark layers, there has been speculation that their formation might be tied to the planet's orbital climate forcing^{1, 2, 3, 4}. But uncertainties in the deposition timescale exceed two orders of magnitude: estimates based on assumptions of dust deposition, ice formation and sublimation, and their variations with orbital forcing suggest a deposition rate of 10^-3 to 10^-2 cm yr^-1 (refs 5, 6), whereas estimates based on cratering rate result in values as high as 0.1 to 0.2 cm yr^-1 (ref. 7). Here we use a combination of high-resolution images of the polar layered terrains⁸, high-resolution topography⁹ and revised calculations of the orbital and rotational parameters of Mars to show that a correlation exists between ice-layer radiance as a function of depth (obtained from photometric data of the images of the layered terrains) and the insolation variations in summer at the martian north pole, similar to what has been shown for palaeoclimate studies of the Earth^{10, 11, 12}. For the best fit between the radiance profile and the simulated insolation parameters, we obtain an average deposition rate of 0.05 cm yr^-1 for the top 250 m of deposits on the ice cap of the north pole of Mars.

1. Astronomie et Systèmes Dynamiques, IMC-CNRS UMR8028, 77 Av. Denfert-Rochereau, 75014 Paris, France
2. Department of Geological Sciences, Brown University, Providence, Rhode Island 02912, USA

Correspondence to: Jacques Laskar¹ Correspondence and requests for materials should be addressed to J.L. (e-mail: Email: laskar@bdl.fr).