Moderate resolution (~30 km) thermal inertia estimates have been made for several regions in the northern hemosphere of Mars. Examples of these maps are presented here for the region O¿-45¿N, O¿-90¿W. The thermal inertia of Kasei Vallis is found to be significantly higher than that of the surrounding terrain. The assumption of a uniform grain size surface gives maximum diameters of 1.0 mm inside and 0.05mm outside Kasei Vallis for the surface materials. high inertia regions are well correlated with low albedo (A~0.14) regions. Three large channels in the Oxia Palus quandrangle also have high inertia floors. There is some indication that the thermal inertia increases toward the mouth of one of these channels. The Chryse and Acidalia basins have uniform high inertia surfaces with no decrease in inertia as distance increases from the major channels. There are numerous craters in the region which have high inertia-low albedo features on the crater floor. This correlation has been observed for many other craters on Mars, both from Mariner 9 and Viking data. A possible explanation is the accumulation of coarse-grained, windblown material within the craters. Average grain sizes of these materials range from 0.5 to 1.1. mm, corresponding to medium to coarse sand. The Viking 1 landing site is located in the lowest inertia region within the area studied which met the latitude and elevation capabilities of that vehicle.