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.

2024 December 3
Ice clouds are seen over the surface of Mars on the upper
right. Toward the lower left is a bright spot in the sky which
is likely the Sun setting through Martian dust. 
Please see the explanation for more detailed information.

Ice Clouds over a Red Planet
Image Credit: NASA, JPL-Caltech, Kevin M. Gill; Processing: Rogelio Bernal Andreo

Explanation: If you could stand on Mars -- what might you see? You might look out over a vast orange landscape covered with rocks under a dusty orange sky, with a blue-tinted Sun setting over the horizon, and odd-shaped water clouds hovering high overhead. This was just the view captured last March by NASA's rolling explorer, Perseverance. The orange colouring is caused by rusted iron in the Martian dirt, some of which is small enough to be swept up by winds into the atmosphere. The blue tint near the setting Sun is caused by blue light being preferentially scattered out from the Sun by the floating dust. The light-coloured clouds on the right are likely composed of water-ice and appear high in the Martian atmosphere. The shapes of some of these clouds are unusual for Earth and remain a topic of research.

Tomorrow's picture: driveway sunspots


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