The Temperature of Mars

Abstract

IN a recent paper (Pub. Ast. Soc. of the Pacific), Nicholson and Pettit calculate the temperature of the planet Mars, based on their radiation measures made at Mount Wilson. Most confidence is placed on measures made in the region 8 to 14μ, by the use of filter screens, and an emissivity of unity is assumed for all wave-lengths. However, Mars, being probably composed of material not unlike the earth, would radiate more like sand or quartz than like a black body, and it can be calculated from curves given by Wood (“Physical Optics”) and data given by Rosenthal (Wied. Ann. 68, p. 783), that the average ratio of the emissivity of quartz to that of a black body in the region 8 to 14μ, is 0.819. The values of the emissivity of quartz given are far below that of a black body between 8 and 10μ ; they are nearly the same from 10 to 14μ; the average ratio is taken.