Question: How smooth must a surface be to produce specular reflection, and do Lunar boot prints meet this standard?
A recent post on Space Exploration asked why footprints on the moon displayed specular reflection. https://space.stackexchange.com/questions/64682/why-do-the-bootprints-on-the-moon-appear-bright-in-some-photographs-or-film
Surfaces displaying specular reflection are (supposedly) flat to within a fraction of the wavelength being reflected. Visible light has a wavelength of about 0.7 microns, but grains of regolith have a size of roughly 70 microns.
Do boot prints reduce the size of regolith a hundred-fold, or is there more to the specular reflection than the wavelength rule?
Even dry asphalt produces specular relections. Asphalt is obviously not smooth to within 0.7 microns. This effect is prominent enough that computer modeling for PBR imaging takes it into account.