High-Resolution Stratigraphy of the Mars North Polar Layered Deposits

Abstract

The Mars north polar layered deposits (NPLD) consist primarily of water ice and dust, and represent the bulk of the north polar cap [Byrne, 2009]. The NPLD likely hold the most extensive record of recent climate during a period of major insolation variation tied to quasiperiodic orbital changes [Thomas et al., 1992; Laskar et al., 2002]. Data from the High Resolution Imaging Science Experiment (HiRISE) permits definition of layers at sub-meter scale and a renewed analysis of possible orbital expression in NPLD thickness. In this study, imagederived digital elevation models are generated and used to produce thickness measurements in accordance with bed orientation and topographic expression. Stratigraphic columns have been produced for two new sites within the NPLD, and contain several sets of finely bedded units 1-2 m thick; dark, prominent marker beds 3-5 m thick; and undifferentiated units. This work suggests that 1-2 m beds are indeed common in the NPLD; that marker beds are also common, but occur at variable separation distances; and that models of NPLD formation need to incorporate new phenomena to generate the observed scale of bedding. As yet, no distinct orbital fingerprint can be identified.