Temperature

Differing values have been reported for the average temperature on Mars,^[10] with a common value being −55 °C.^[11] Surface temperatures have been estimated from the Viking Orbiter Infrared Thermal Mapper data; this gives extremes from a warmest of 27 °C to −143 °C at the winter polar caps.^[12] Actual temperature measurements from the Viking landers range from −17.2 °C to −107 °C.

It has been reported that "On the basis of the nighttime air temperature data, every northern spring and early northern summer yet observed were identical to within the level of experimental error (to within ±1 K)" but that the "daytime data, however, suggest a somewhat different story, with temperatures varying from year-to-year by up to 6 K in this season.^[13] This day-night discrepancy is unexpected and not understood". In southern spring and summer variance is dominated by dust storms, which increase the value of the night low temperature and decrease the daytime peak temperature,^[14] resulting in a small (20C) decrease in average surface temperature, and a moderate (30C) increase in upper atmosphere temperature