GEOMORPHIC MAPPING OF THE BASEMENT UNIT WITHIN THE NORTHEAST SYRTIS MARS 2020 LANDING ELLIPSE

The NE Syrtis Mars 2020 landing ellipse contains diverse geology and aqueous mineralogy bracketed by the Late Noachian Isidis basin and the Early Hesperian Syrtis Major lavas. The NE Syrtis “basement unit” is dated to the Late Noachian and preserves some of the oldest crustal materials exposed on the surface of Mars today. Megabreccia exposures in the basement also provide a record of pre-Isidis materials and stratigraphy. This basement unit exhibits diverse characteristics including ridges, fractures, brecciation, and smooth textures, and also contains a heterogeneous distribution of low-Ca pyroxene, Fe/Mg phyllosilicate, and occasional Al phyllosilicate. These clays record past water-rock interactions and may also preserve biosignatures, which are an important focus for potential sample return from the Mars 2020 mission. Rover investigations of this basement unit would greatly enhance our understanding of the ancient martian environment and major transitions in Mars’ climate.

Here we present geomorphic mapping of the NE Syrtis landing ellipse and use HiRISE and CRISM observations to determine the distribution of Fe/Mg and Al clays within the basement unit. Mapped units in the basement include ridged/fractured, brecciated, rugged, and smooth materials, in addition to discrete megabreccia exposures. Fe/Mg clays are found only in the basement, though they are not ubiquitous throughout the unit, either due to a true absence of clay in areas of the basement exposure or due to dust, sand, or cover obscuring the clay signatures. Detailed correlation of the geomorphic map with the CRISM detections may help determine the reason for the spectral presence or absence of Fe/Mg clay within the basement units. Very few detections of Al clay are found within the ellipse, although several exposures with stronger spectral signatures are found just beyond the ellipse. Mapping these basement subunits is also useful for constraining possible sampling sites with the Mars 2020 payload. From the Mars Science Laboratory experience, regions that appear smooth-textured from orbit are often associated with ex-situ rubbly, unconsolidated sands and gravel that are difficult to place in geologic context. Hi-resolution orbital mapping can therefore help maximize the scientific return from a future Mars 2020 mission.