Preliminary Infrared Radiometry of the Night Side of Mercury from Mariner 10

See allHide authors and affiliations

Science  12 Jul 1974:
Vol. 185, Issue 4146, pp. 142-145
DOI: 10.1126/science.185.4146.142


The infrared radiometer on Mariner 10 measured the thermal emission from the planet with a spatial resolution element as small as 40 kilometers in a broad wavelength band centered at 45 micrometers. The minimum brightness temperature (near local midnight) in these near-equatorial scans was 100°K. Along the track observed, the temperature declined steadily from local sunset to near midnight, behaving as would be expected for a homogeneous, porous material with a thermal inertia of 0.0017 cal cm-2 sec °K-1, a value only slightly larger than that of the moon. From near midnight to dawn, however, the temperature fluctuated over a range of about 10°K, implying the presence of regions having thermal inertia as high as 0.003 cal cm-2 sec-½ °K-1.