Sedimentary geomorphology of the Mars Pathfinder landing site

Abstract

The first landing on Mars in over 20 years will take place July 4, 1997, near the mouth of the Ares Vallis outflow channel located in southeastern Chryse Planitia. Mars Pathfinder, unlike Viking 1, is expected to land on a surface that has a distinct and unambiguous fluvial signature. For safety reasons, the landing site was selected within a broad plains region beyond the mouth of Ares Vallis so as to avoid large topographic obstacles that could pose hazards to the landing. However, this plain is not without its interesting, and in some cases rather problematic, landforms. The 100 km by 200 km landing ellipse contains the following features: (1) primary impact craters, (2) clusters of small secondary craters, (3) streamlined islands, (4) longitudinal grooves, (5) “scabland” or “etched” terrain, (6) pancake‐like shields and dike‐like structures, (7) knobs or buttes, and (8) a previously undetected, subtle undulating or hummocky texture to the plains surface. The nature of these landforms has important bearing on how we will interpret what we see at the scale of the Pathfinder lander once the first images are transmitted to Earth. With the exception of the craters, all of the remaining features described within the Mars Pathfinder landing ellipse can be interpreted as forming as a result of catastrophic flooding from Ares and Tiu Valles into Chryse Planitia, either during the flood itself, or through secondary modification of thick flood deposits after the event.