The Mars Pathfinder Lander measures air temperature with sensors located on the Meteorological mast at 10, 20, and 40 inches, (0.25, 0.50, 1.0 meters) above the solar panel. Air temperatures measured during the first three days of the mission show an afternoon high near 14 degrees Fahrenheit (264 Kelvin). [The 270 degree Kelvin temperatures measured at noon on Sol 1 were obtained while the mast was still lying down just above a warm solar panel]. During the day, the air temperatures measured by the lowest of the 3 sensors are 9 to 10 degrees Fahrenheit (5 to 6 Kelvin) warmer than those measured by the top sensor because the atmosphere is heated bythe sunlit surface below it. At night, the ground cools more quickly than the atmosphere, and the warmest air temperatures are measured by the uppermost temperature sensor. These temperature differences provide information about the exchange of heat between the surface and the atmosphere. The Viking landers could not determine this quantity directly because they measured the air temperature at only one height (64 inches or 1.6 meters). The air temperatures measured by Pathfinder are slightly warmer than those seen 21 years ago at the nearby Viking Lander 1 site at the same Martian season. This may result because the somewhat darker surface at the Pathfinder landing site absorbs more sunlight than the Viking 1 Landing site.