Tracks of dust devils spotted from space.

Scientists scanning satellite images of the southern Sahara have detected trails left on the landscape by the whirlwinds commonly known as dust devils, the first such observations made from Earth orbit. Cameras on several spacecraft that have landed on Mars have spotted such whirlwinds, and some images of the Red Planet from orbit show shadows cast by dust-filled funnel clouds, says Angelo Pio Rossi of the International Research School of Planetary Sciences in Pescara, Italy. When Rossi and his colleague Lucia Marinangeli looked at satellite photos of Earth for similar tracks, they found them on images of central Niger. Repeated images of the same locale at different times indicate that the tracks last, at most, only a few weeks. Researchers suggest that the windswept tracks reflect less sunlight than normal because the dust devils whisk away dust and small sand grains.