  Our current knowledge of life on Earth indicates a basic requirement for
liquid water. The locations of present liquid water are therefore the logical
sites to search for current life on Mars. We develop a picture of where on Mars
the regions with the highest potential near-surface liquid water abundance can
be found through a study of gullies. We also use rampart craters to sound the
depth of water ice on Mars and where the highest concentrations of water ice
occur. We estimate that low latitude gullies and rampart craters with depths
greater than 100 m at 30 degrees (absolute) latitude, greater than 1.3 km at 35
degrees and greater than 2.6 km at 40 degrees latitude will give access to
current liquid water environments capable of supporting microbial life. Our
data is most consistent with the formation of these gullies through shallow
aquifer discharge. These features should therefore be high priority targets for
further study and high-resolution imaging with HiRISE.
