Moon and Mars

StarDate: August 2, 2014

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Mars is known as the Red Planet. But that overstates its color. Much of the Martian surface is orange, tan, or butterscotch. It’s colored by a thin layer of iron-rich dust.

The color of the Martian sky is a little trickier to pin down. Pictures from landers and rovers show everything from blue to yellow to deep orange.

In part, that’s because the pictures are taken at different times of day and at different Sun angles, so the colors change — just as the sky here on Earth can change from bright blue at mid-day to orange and gold at sunset.

Another reason for the variation is the way the pictures are snapped and processed. Most of them are compiled from black-and-white images that are shot through filters. Different sets of filters, and different processing techniques, can yield different colors.

The true color of the mid-day sky is probably yellowish-brown — tinted by the same dust as the surface. The dust grains are tiny and easily blown around, so it’s probably rare for there to be no dust in the sky.

Without the dust, the atmosphere is so thin that there’s not much material to scatter sunlight. So instead of bright blue, a dust-free Martian sky would probably look dark blue or even black — perhaps dark enough to see a few stars twinkling through the daylight.

Mars isn’t visible during daylight here on Earth, but it is visible as night falls this evening, to the left of the Moon — an orange pinpoint shining through our own black sky.

 

Script by Damond Benningfield, Copyright 2014

For more skywatching tips, astronomy news, and much more, read StarDate magazine.

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