# Is the sunlight reflected off of either the atmosphere or surface of a planet polarized?

Is the reflecting off of the surface of the terrestrial planets (those with or without an atmosphere), or the gas- or ice-giants, polarized, or unpolarized like the sunlight before it is reflected?

• It's really hard to make non-normal reflection completely unpolarized or completely polarized, so the answer is going to be "ya, somewhat, depending." Can you explain why this question is related to Space Exploration in some way? It's a great fit in Astronomy SE, but a one-sentence question about the interaction of light with rock, gas, and aerosols doesn't seem to have any Space Exploration aspects at all. – uhoh Mar 23 '20 at 0:53
• Also, for the latter two see the polarization aspects of Rayleigh scattering and Mie scattering/ – uhoh Mar 23 '20 at 0:56
• @uhoh I was thinking it fit under planetary sciences, but I forgot to include the tag. – Bob516 Mar 23 '20 at 3:14

## 1 Answer

The answer is "it's complicated." If you start with Snell's Law(s) , they show that the degree of polarization at an interface depends both on the ratio $$\frac{n_2}{n_1}$$ and on the angle of incidence.

Next, you have to deal with the nonuniform atmosphere (if any), and the properties of whatever reflective & transmissive materials are on the surface. As uhoh's comment points out, Rayleigh and Mie scattering cause polarization as well, which is why we use polarizing material in some sunglasses. Get a pair, and on a sunny day rotate them: you'll see significant difference in the transmitted power with angle.

• Polarizing filters are used for cameras too, they could be rotated to get a little darker and colourful sky. – Uwe Mar 23 '20 at 15:40