The objective of this paper is to determine whether martian landslides in Valles Marineris were wet or dry and place constraints on the availability of liquid water in Valles Marineris during the Amazonian, when the landslides occurred. We, thus, statistically compare the power-law relationship between the volume and runout distance of landslides on Earth with those in Valles Marineris, Mars. The exponent of the power-law for martian landslides is similar to that for dry landslides and volcanic flows on Earth, and differs significantly from wet debris flows on Earth. The constant of proportionality in the observed power-law relationship for martian flows is linearly proportional to gravity, as predicted from physical modeling of dry flows in which the dissipation occurs in a layer of uniform thickness. Conversion of gravitational potential energy to heat is insufficient to generate more than a few weight percent of liquid water in the landslide. We thus conclude that water did not significantly influence the dynamics of landslides in Valles Marineris. This implies predominantly dry conditions in Valles Marineris during the Amazonian.