Topographic Map of MFF Deposits

Close to Mars’s equator lies the deposits of the Medusae Fossae Formation (MFF), a fascinating wind-sculpted series of deposits. When Mars Express turned its MARSIS radar sounder instrument on over the MFF, it revealed a surprise. The radar signals that echoed back match what we’d expect to see from layered deposits rich in water ice like the polar layered deposits that makeup the Martian polar caps.

In this image, the white horizontal line on the colored topographic map of Mars’s surface (top) shows a narrow stretch of land that was scanned by MARSIS. The pop out below shows the radar data collected by the instrument that reveals the subsurface; the brighter the area, the stronger the radar echo received from that area. The white line covers two thick mounds separated by a valley. These mounds are clearly visible in the radar data below. Analysis of the radar data suggests that beneath a thick layer of dry material (likely volcanic ash or dust), the mounds are rich with water ice.