REGOLITH LANDFORM MAPPING OF MERIDIANI PLANUM AND SURROUNDS J. D. A. Clarke 1 C. F. Pain 2 and M. Thomas 1, 1 Australian Centre for Astrobiology, Macquarie University, NSW 2109, Australia, 2 4 Sticht Place, Florey ACT 2615, Australia

What is Regolith? “Regolith” is a general term used to refer to all weathered earth surface materials extending from the interface with unweathered bedrock at depth to the surface. “Regolith” is a general term used to refer to all weathered earth surface materials extending from the interface with unweathered bedrock at depth to the surface. It includes in situ weathered material derived directly from the underlying bedrock, and transported material derived from both bedrock and other regolith materials It includes in situ weathered material derived directly from the underlying bedrock, and transported material derived from both bedrock and other regolith materials Landforms are used as a proxy for the largely hidden regolith – this means understanding the dynamics of past and present landscapes Landforms are used as a proxy for the largely hidden regolith – this means understanding the dynamics of past and present landscapes

Regolith on Mars Transported regolith is common on Mars, and can be recognized by its similarities to Earth regolith Transported regolith is common on Mars, and can be recognized by its similarities to Earth regolith Fans and alluvial features Fans and alluvial features colluvial material such as talus deposits colluvial material such as talus deposits wind-blown sand, volcanic ejecta, and ejecta from impact craters wind-blown sand, volcanic ejecta, and ejecta from impact craters Intensely weathered in situ regolith owes its origin to long periods of geomorphic stability, and to the presence of water. Regolith resulting from intense chemical weathering may well be locally common on Mars Intensely weathered in situ regolith owes its origin to long periods of geomorphic stability, and to the presence of water. Regolith resulting from intense chemical weathering may well be locally common on Mars

Regolith Landform Mapping A regolith landform map shows the distribution of material at the surface A regolith landform map shows the distribution of material at the surface It uses images derived from a range of ground, airborne and spaceborne platforms It uses images derived from a range of ground, airborne and spaceborne platforms Map polygons are based on interpretation of landforms and their associated regolith materials Map polygons are based on interpretation of landforms and their associated regolith materials Where possible ground observations are used for verification Where possible ground observations are used for verification

Morphostratigraphic map of Meridiani Terra (Hynek et al.) 900 km E-W, with 12 mapping units based largely on age and surface texture

70km west of the Opportunity landing site 3 km across, allowing much more detail to be mapped. Each unit in the preceding map can be subdivided on the basis of regolith materials inferred from landforms

Opportunity landing site Surface detail of one mapping unit, where a thin veneer of aeolian sand overlies eroded sediments

Opportunity landing site Locally intense chemical weathering producing onion skin weathering

Last words Most geoscience studies of the Martian surface emphasize geology and mineralogy Most geoscience studies of the Martian surface emphasize geology and mineralogy A knowledge of regolith will be fundamental to human explorers on Mars, because they will land on it, set up bases on it, and travel over it. A knowledge of regolith will be fundamental to human explorers on Mars, because they will land on it, set up bases on it, and travel over it. In spite of the hundreds of thousands of orbital and rover images of the Martian surface now available, interpretation of landforms and regolith on Mars is dependant on comparison with Earth analogues, and on models that make assumptions about environmental conditions and the nature of regolith materials In spite of the hundreds of thousands of orbital and rover images of the Martian surface now available, interpretation of landforms and regolith on Mars is dependant on comparison with Earth analogues, and on models that make assumptions about environmental conditions and the nature of regolith materials It is clear that a proper understanding of the Martian regolith will only be achieved when human explorers get their hands on it. It is clear that a proper understanding of the Martian regolith will only be achieved when human explorers get their hands on it.