Mercury's Thermal Environment

extracted from Thermal Environments JPL D-8160

The following table summarizes the range of Direct Solar, Reflected Solar (Albedo), and Planetary Infrared for the planet Mercury.


                 Perihelion       Aphelion         Mean
----------------------------------------------------------------
Direct Solar     14462 W/sqM      6278 W/sqM      9126 W/sqM

Albedo             0.12             0.12            0.12
(subsolar peak)

Planetary IR.     12700 W/sqM      5500 W/sqM      8000 W/sqM
(dark side Min)   6 W/sqM          6 W/sqM         6 W/sqM

Mercury's sidereal orbit period (it's year) is about 88 Earth days and its period of rotation is ~58 Earth days. This lead to a Mercurian day of 176 Earth days. This effectively means that the rotation is so slow, that the side facing the Sun is essentially in thermal equilibrium as is the dark side. Thus, the surface temperature can be described such that the planetary emission falls off from the subsolar region to the limb as a cosine function. Assume the emittance is ~ 0.77

The albedo of Mercury is generally low but bright craters and rays can be up to 0.25 as shown below.

                   NORMAL ALBEDO
---------------------------------------------------
Bright Craters and Rays              0.19 to 0.25

Heavily Cratered Terrain             0.11 to 0.19
and Textured Plains    

Flat-floored Plains                  0.10 to 0.13

Smooth Plains                        0.08 to 0.12

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