On an airless world like Slag there were no atmospheric particles to diffuse sunlight into places the sun itself did not reach.

Beyond (above) this, the exosphere describes the thinnest remainder of atmospheric particles with large mean free path, mostly hydrogen and helium.

Optical systems analysis has been conducted for four decades, starting in the 1960s with satellite imagery and laser light scattering from atmospheric particles.

Species that depended on photosynthesis declined or became extinct as atmospheric particles blocked sunlight and reduced the solar energy reaching the Earth's surface.

Instead, they interact with the nuclei of atmospheric particles and cause a cascade of particles, known as an air shower.

I think he was looking at high-level atmospheric particles.

When sunlight interacts with atmospheric particles much smaller than the wavelength of visible light, a phenomenon known as Rayleigh scattering occurs.

This high energy radiation is absorbed by atmospheric particles, raising them to excited states and knocking electrons free in the process of photoionization.

The scattering that produces the veil, or haze, occurs when light is deflected by atmospheric particles.

Therefore the phase curve may constrain other planet properties, such as the particle size distribution of the atmospheric particles.