Radar sounding of Lucus Planum, Mars, by MARSIS

Radar sounding data over Lucus Planum were analyzed to derive bulk dielectric properties Results support the interpretation of a volcanic origin for those areas in which echoes from the base of Lucus Planum could be detected Lucus Planum is laterally inhomogeneous, implying that it originated from multiple events and/or processes Radar sounding data over Lucus Planum were analyzed to derive bulk dielectric properties Results support the interpretation of a volcanic origin for those areas in which echoes from the base of Lucus Planum could be detected Lucus Planum is laterally inhomogeneous, implying that it originated from multiple events and/or processes Lobe†shaped thick deposits, collectively known as the Medusae Fossae Formation, are found west of the Olympus Mons volcano on Mars. Visual observations of these smooth and relatively unremarkably looking materials have not definitively determined how they formed with hypotheses ranging from volcanic ash to remnants of a materials deposited at a previous location of the north pole, to accumulation of atmospheric dust. In this study we used the ground penetrating radar on board Mars Express to see through these deposits to derive information about Lucus Planum, the central lobe of the Medusae Fossae Formation. Through our analysis of the way the radar waves were reflected by subsurface layering, we concluded that the materials forming Lucus Planum are spatially variable: the east and west portions of the deposits are highly porous and probably composed of ashes and rocks from nearby volcanoes. In the north†west the deposits are much denser, but we could not unequivocally define their nature. Finally, our instrument could not detect signals from the central part of Lucus Planum, which suggests yet a different component in the deposits. This diversity points to a dynamic geological history in this unique region of Mars.