Phenomenon of glory and constraints it places on microphysics of aerosols in the atmosphere of Venus

We investigate the interrelation between the size distribution of sulfuric-acid droplets and the phenomenon of the glory surge on the phase function near backscattering, with special emphasis on photometric observations of Venus at λ = 0.365 μm. We use the Lorenz-Mie theory to compute light scattering by single spheres with a radius spanning the range from r = 0.01 μm up to 7.5 μm and apply a power-law size distribution ñ(r) ∝ r^-n to this polydisperse particle system. Our modeling reveals a weak dependence of the light-scattering response on the bottom limit of the power-law size distribution when it is set to be sufficiently small, r_min ≤ 0.1 μm. There is a straightforward interrelation between the upper limit r_max and the phase-angle location of the glory, which can be easily parameterized with a polynomial. The resulting interrelation can be used for immediate retrievals of r_max of aerosols in the atmosphere of Venus using observations of its glory phenomenon. We also show that the surge of the glory compared to that of the backscattering peak helps identify the chemical composition between water and sulfuric acid droplets remotely.