GROUND PENETRATING RADAR FOR MARS SUBSURFACE INVESTIGATIONS

Ground-penetrating radar (GPR) is recognized as an efficient tool for non-invasive exploration of radar properties associated with subsurface stratigraphy to depths of 10s of meters. For more than 30 years, GPR has been used in many geological and archeological studies on Earth to characterize how shallow stratigraphy and structure in various geologic settings vary with depth and areal extent. Additionally, GPR location of buried bedrock or other interesting features can be used to target drilling or excavation projects. Recently, GPR has been discussed increasingly for possible inclusion on a Mars rover. Whereas the SHARAD and MARSIS orbital radar sounders may penetrate hundreds of meters to several kilometers, respectively, a rover-mounted GPR would penetrate 10s of meters but would provide the vertical and horizontal resolution necessary to interpret the geologic setting and history of a landing site.

The Strata instrument is a low mass, low power, low volume Mars GPR prototype operating at 400 MHz (75 cm wavelength). Data have been collected in various geologic settings to demonstrate the utility of GPR for characterizing the subsurface and to quantify the quality of data measured with the prototype. Field tests have taken place in volcanic and cratered terrains in Arizona, arctic permafrost regions with massive ground ice, and paleo glacio-deltaic settings in Maine. Field results show that Strata is highly capable of providing cm-scale vertical resolution data which reveal shallow subsurface geological information to depths of 10-20 m, depending on the setting. As the exploration of Mars continues, detailed studies of local and regional geology will focus on areas that hold clues about the past or present distribution of near surface ice and areas that may be of interest for astrobiological studies. By studying near-surface stratigraphy, structure, and depositional setting, GPR can help define past habitable environments and the biologic potential of a landing site.