Solar Flux on Mars.

The emitted power of Mars is mainly affected by the thermal characteristics of surface and atmosphere. The solar flux is the dominant factor developing the thermal characteristics of Mars’ surface and atmosphere. In addition, the solar flux can help us determine the absorbed solar power with Bond albedo. Therefore, it is necessary to discuss the spatiotemporal variations of solar flux on Mars. There are two dominant factors that influence the distribution of solar flux on Mars: 1) Mars’ axial tilt of 25.19° and 2) the eccentric orbital path Mars follows around the Sun (eccentricity ∼0.0935). Mars’ relatively large axial tilt angle significantly impacts how incident solar radiation is distributed across latitudes, while the large orbital eccentricity affects the Mars–Sun distance and hence the total solar flux. Mars reaches its furthest point from the Sun (∼1.666 AU), or aphelion, during Northern spring (Ls = 71°) and closest point to the Sun (∼1.381 AU), or perihelion, during Northern autumn (Ls = 251°). Considering the two effects (i.e., obliquity and eccentricity), we can calculate the solar flux in the plane of latitude and solar longitude (i.e., season) (SI Appendix, Fig. S1). The global-average solar flux (SI Appendix, Fig. S1B) increases ∼45.4% from ∼123.06 Wm⁻² at aphelion to ∼178.94 Wm⁻² at perihelion. The changes of solar flux at some latitudes can be even more pronounced.