Imaging the subsurface structure of Planum Boreum with the Mars Reconnaissance Orbiter Shallow Radar

We review prior mapping of the subsurface structure of Planum Boreum that was conducted with 2-D sounding data from the Shallow Radar (SHARAD) instrument onboard the Mars Reconnaissance Orbiter (MRO). Widespread reflections from basal and internal interfaces of the north polar layered deposits (NPLD) occur throughout the 1,000,000-km² area. A dome-shaped zone of diffuse reflectivity up to ~1 km thick underlies two-thirds of the NPLD. This zone is associated with a basal unit identified in image data as Amazonian sand-rich layered deposits. In other areas, the NPLD base is remarkably flat-lying and co-planar with the exposed surface of the surrounding Vastitas Borealis materials. Within the NPLD, radar-layer packets that extend throughout the deposits have been mapped as five units with a total volume of 821,000 km³, exclusive of the basal unit. Application of a 3-D imaging technique commonly used in processing seismic data to the polar grid of 2-D SHARAD observations is expected to yield an improved representation of the subsurface layering geometry and greatly reduce the effects of surface clutter.