# Refractive index of Martian atmosphere near surface

Hi folks,
Does anyone have a good reference for the refractive index of the near surface Martian atmosphere?
(Or alternatively, the means to estimate it from readily available data!)

I'm struggling to think of an equation for which I've got enough of the variables to be of use, (for example assuming the atmosphere is CO2, and the pressure is ~6mbar, temperature etc.)

Hope you'll be able to help. Thanks in advance!

Janus
Staff Emeritus
Gold Member
Thanks very much for your reply Janus. But am I missing something obvious? The section taken largely from Birch & Downs's "Correction to the Updated Edlh Equation for the Refractive Index of Air" deals specifically with air rather than CO2, and the tables don't give values for CO2 the pressure regime at the Martian surface.

http://www.ps.missouri.edu/rickspage/refract/refraction.html

CO2 n=1.000449 according to this page, but the page explicitly says the numbers are a guideline only and as far as I can tell there are no references. Since I am assuming this n value is at 1atm, you will have to convert the value to reflect the difference pressure at Mars' surface. I am not sure what forumula will help you do this, I am curious about this too, so if you find the formula post it for me.

Cheers.

DaveC426913
Gold Member
Mars' atmo is 49 parts vacuum to 1 part air

I would think its refractive index is effectively 1.

Mars' atmo is 49 parts vacuum to 1 part air

I would think its refractive index is effectively 1.

Dave, is that at the surface of Mars?