Evidence for aggregate particles in the atmospheres of Titan and Jupiter

Calculations of the optical properties of aggregate particles are able to resolve a persistent problem in understanding the shape and size of haze aerosols in the atmospheres of Titan and Jupiter. Most of the photometric and polarimetric observations for Titan can be explained by the presence of aggregate particles whose mean projected area is equal to that of a sphere with radius 0.14 μm, containing monomers with mean radii near 0.06 μm. An additional mode of smaller particles is needed to fit ultraviolet data. Aggregate particles can also account for the observed optical properties of Jupiter's high altitude haze. Knowledge of the size and shape of the particles will allow for more precise estimates of the sedimentation rates and provide a key constraint on the coupled surface/atmosphere evolution of Titan.