  Recent discoveries of anomalously bright radar reflections below the Mars
South Polar Layered Deposit (SPLD) have sparked new speculation that liquid
water may be present below the ice cap. The reflections, discovered in data
acquired by the Mars Advanced Radar for Subsurface and Ionospheric Sounding
(MARSIS) on board the Mars Express orbiter, were interpreted as reflections
from damp materials or even subsurface ponds and lakes similar to those found
beneath Earth's ice sheets. Recent studies, however, have questioned the
feasibility of melting and maintaining liquid water below the SPLD. Herein, we
compare radar simulations to MARSIS observations in order to present an
alternate hypothesis: that the bright reflections are the result of
interference between multiple layer boundaries, with no liquid water present.
This new interpretation is more consistent with known conditions on modern
Mars.
