September 24, 2019
Somewhere above you, light is arriving from places so distant their names feel like poetry.
Sand Dunes Thawing on Mars
Birthday · September 24, 2019
A little universe, just for you
Your date.
Ready to give.
Free PNG · 1080 × 1350 · No account needed
Image rights and credit requirements apply when sharing or reusing imagery.
Date & occasion only
Change the year
APOD published September 24, 2019. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.
What are these strange shapes on Mars? Defrosting sand dunes. As Spring dawned on the Northern Hemisphere of Mars, dunes of sand near the pole, as pictured here in late May by ESA's ExoMars Trace Gas Orbiter, began to thaw. The carbon dioxide and water ice actually sublime in the thin atmosphere directly to gas. Thinner regions of ice typically defrost first revealing sand whose darkness soaks in sunlight and accelerates the thaw. The process might even involve sandy jets exploding through the thinning ice. By Summer, spots will expand to encompass the entire dunes. The Martian North Pole is ringed by many similar fields of barchan sand dunes, whose strange, smooth arcs are shaped by persistent Martian winds. Create a Distant Legacy: Send your name to Mars.