Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2015 May 12
See Explanation.  Clicking on the picture will download
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Two Worlds, One Sun
Left Image Credit & Copyright: Damia Bouic;
Right Image Credit: NASA, JPL-Caltech, MSSS; Digital processing: Damia Bouic

Explanation: How different does sunset appear from Mars than from Earth? For comparison, two images of our common star were taken at sunset, one from Earth and one from Mars. These images were scaled to have same angular width and featured here side-by-side. A quick inspection will reveal that the Sun appears slightly smaller from Mars than from Earth. This makes sense since Mars is 50% further from the Sun than Earth. More striking, perhaps, is that the Martian sunset is noticeably bluer near the Sun than the typically orange colors near the setting Sun from Earth. The reason for the blue hues from Mars is not fully understood, but thought to be related to forward scattering properties of Martian dust. The terrestrial sunset was taken in 2012 March from Marseille, France, while the Martian sunset was captured last month by NASA's robotic Curiosity rover from Gale crater on Mars.

Tomorrow's picture: magnificent horse

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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