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.

2025 June 15
Two images are shown side by side. On the left is
a sunset seen from Earth, while on the right is a sunset
seen from Mars. The Earth sunset is quite orange, while
the Mars sunset is quite blue. The Sun appears angularly
smaller from Mars than from the Earth. 
Please see the explanation for more detailed information.

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 the same angular width and are 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 in 2015 by NASA's robotic Curiosity rover from Gale crater on Mars.

APOD Turns 30!: Free Public Lecture in Cork, Ireland on June 24
Tomorrow's picture: S30E1


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