Mariner 10 infrared radiometer results: Temperatures and thermal properties of the surface of Mercury

Mariner 10 infrared brightness temperatures of the surface of Mercury at 11 and 45 μm are presented. The data were obtained during the first flyby along a nera-equatorial swath extending from 17 hours local time through local midnight to 9 hours local time. For an assumed emissivity of 0.9, derived surface thermal inertias are between $\text{0.0031}\text{and}\text{0.0031}\text{cal cm}{}^{\mathrm{?2}}\text{sec}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}\text{K}{}^{\mathrm{?1}}$ and the implied minimum predawn surface kinetic temperature for the warm pole at longitude 270° is near 93 K. Several pronounced thermal inhomogeneities were seen, one of which appears to coincide with a region of high radar reflectivity. The derived thermal properties and the electrical skin depth and loss tangent fall within the range of values found on the Moon.