Surface properties of Mars' polar layered deposits and polar landing sites

On December 3, 1999, the Mars Polar Lander and Mars Microprobes will land o n the planet's south polar layered deposits near (76 degrees S, 195 degrees W) and conduct the first in situ studies of the planet's polar regions. Th e scientific goals of these missions address several poorly understood and globally significant issues, such as polar meteorology, the composition and volatile content of the layered deposits, the erosional state and mass bal ance of their surface, their possible relationship to climate cycles, and t he nature of bright and dark aeolian material. Derived thermal inertias of the southern layered deposits are very low (50-100 J m(-2) s(-1/2) K-1), su ggesting that the surface down to a depth of a few centimeters is generally fine grained or porous and free of an appreciable amount of rock or ice. T he landing site region is smoother than typical cratered terrain on similar to 1 km pixel(-1) Viking Orbiter images but contains low-relief texture on similar to 5 to 100 m pixel(-1) Mariner 9 and Mars Global Surveyor images. The surface of the southern deposits is older than that of the northern de posits and appears to be modified by aeolian erosion or ablation of ground ice.