  The detection of liquid water by the Mars Advanced Radar for Subsurface and
Ionosphere Sounding (MARSIS) at the base of the south polar layered deposits in
Ultimi Scopuli has reinvigorated the debate about the origin and stability of
liquid water under present-day Martian conditions. To establish the extent of
subglacial water in this region, we acquired new data, achieving extended radar
coverage over the study area. Here, we present and discuss the results obtained
by a new method of analysis of the complete MARSIS dataset, based on signal
processing procedures usually applied to terrestrial polar ice sheets. Our
results strengthen the claim of the detection of a liquid water body at Ultimi
Scopuli and indicate the presence of other wet areas nearby. We suggest that
the waters are hypersaline perchlorate brines, known to form at Martian polar
regions and thought to survive for an extended period of time on a geological
scale at below-eutectic temperatures.
