Friday, March 8, 2013

martian sunset

many humans wish to take the long journey to mars, to stand on another planet, feel gravity differently, watch dust devils zooming by, and see a strange-colored sky overhead.  

since mars has a thin atmosphere, it should have a blue sky due to rayleigh scattering, but mars also has a lot of airborne dust as well.  the dust absorbs the blue and causes its sky to look somewhere between a butterscotch and pink.  

it turns out to be a challenge to know the exact color our eyes would see a martian sky to be, because none of our eyes have ever seen it directly.   we are left to reconstruct images from the limited filters on the martian rovers, and it is not a trivial task to make those look like they might to our eye.

you may have been expecting a hazy or reddish sky on mars, but were you expecting the sunsets to look blue?

taken by mars pathfinder on 22nd june 1996 (JPL/NASA)
the blue color is likely caused by some blue light being scattered by the dust as the light goes through the long distance towards the horizon at sunset.  

from the spirit rover (NASA/JPL/Texas A&M/Cornell)
and... dust devils!!

dust devils captured by NASA's spirit rover in may 2005. (NASA/JPL-Caltech/Cornell/USGS)

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