MARS OCEAN SHORELINE MAPPING: STRATEGIES AND PRELIMINARY RESULTS

We present the current status of our global shoreline map, which consists of GIS shapefiles representing proposed shorelines. This map uses the global digital elevation model (DEM) of MGS Mars Orbiter Laser Altimeter (MOLA) data, merged with DEMS from from the Mars Express Camera (HRSC) and gridded at 200 m/pixel (Fergason, et al., 2018). For global imagery, the 6 m/pixel image mosaic of Context Imager (CTX) data on MRO was used, compiled by Dickson et al. (2018).

We’ve identified more than a dozen distinct levels at elevations ranging from -4000 meters to +1200 meters elevation. Due to the precision at which the global CTX mosaic was assembled, and the lower resolution of the global DEM, this study may be necessarily limited to regional and global map scales. Very high resolution DEMs of select terrestrial analogs in SW Utah illustrate the need for high-resolution data to evaluate these features at large scales.

We have begun to extend identification of the higher, less well-preserved proposed shorelines using the CTX global mosaic and HRSC/MOLA global DEM. We have also begun measuring global trends in elevation of the proposed shorelines and inferred water volumes in cubic kilometers and global equivalent layer (GEL) values so that these measurements can be compared with published model predictions of volatile inventory relative to planetary accretion, outgassing, and Late Heavy Bombardment. We will incorporate relative age determinations of the proposed shorelines based on superposition relationships with other geologic surfaces for which ages have been assigned by other researchers based on crater counts. Finally, we will develop and apply geophysical models of surface response to large sediment and water loads. Hypotheses will be developed to explain deviations from equipotential surfaces delineated by the proposed shorelines, that might indicate their isostatic and tectonic de-leveling over geologic time.