These clouds are the most clearly visible so far from Curiosity, which landed five years ago this month about five degrees south of Mars' equator. Clouds moving in the Martian sky have been observed previously by Curiosity and other missions on the surface of Mars, including NASA's Phoenix Mars Lander in the Martian arctic nine years ago.
Mars' elliptical orbit makes that planet's distance from the Sun vary more than Earth's does. In previous Martian years, a belt of clouds has appeared near the equator around the time Mars was at its farthest from the Sun. The new images of clouds were taken about two months before that farthest point in the orbit, relatively early in the season for the appearance of this cloud belt.
"It is likely that the clouds are composed of crystals of water ice that condense out onto dust grains where it is cold in the atmosphere," said Curiosity science-team member John Moores of York University, Toronto, Canada. "The wisps are created as those crystals fall and evaporate in patterns known as 'fall streaks' or 'mare's tails.' While the rover does not have a way to ascertain the altitude of these clouds, on Earth such clouds form at high altitude."
The Curiosity mission has been investigating the environmental conditions of ancient and modern Mars since the rover landed on Aug. 5, 2012, PDT (Aug. 6, EDT and Universal Time). For more about Curiosity, visit:
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