July 6, 2025
Your birthday is not just a date on a calendar. It is the yearly return of a moment when the universe became more observant, more feeling,...
The Spiral North Pole of Mars
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APOD published July 6, 2025. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.
Why is there a spiral around the North Pole of Mars? Each winter this pole develops a new outer layer about one meter thick composed of carbon dioxide frozen out of the thin Martian atmosphere. This fresh layer is deposited on a water-ice layer that exists year round. Strong winds blow down from above the cap's center and swirl due to the spin of the red planet -- contributing to Planum Boreum's spiral structure. The featured image is a perspective mosaic generated in 2017 from numerous images taken by ESA's Mars Express and elevations extracted from the laser altimeter aboard NASA's Mars Global Surveyor mission.