FIG. 2.

Contours of constant planetary flux on an exomoon as a function of the planet-satellite semimajor axis a_ps and the planet's bond albedo α_p. The planet-moon binary orbits at 1 AU from a Sun-like host star. Values depict the maximum possible irradiation in terms of orbital alignment, i.e., on the subplanetary point on the moon, and when the moon is over the substellar point of the planet. For α_p≈0.1 contours of equal f_r and f_t intersect; i.e., both contributions are equal. An additional contour is added at 295 W/m², where the sum of f_r and f_t induces a runaway greenhouse on an Earth-sized moon. Some examples from the Solar System are given: Miranda (Mi), Io, Rhea (Rh), Europa (Eu), Triton (Tr), Ganymede (Ga), Titan (Ti), Callisto (Ca), and Earth's moon (Moon). Color images available online at www.liebertonline.com/ast