Wispy, early-season clouds resembling Earth’s ice-crystal cirrus clouds move across the Martian sky in some new image sequences from NASA’s Curiosity Mars rover.
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.
Researchers used Curiosity’s Navigation Camera (Navcam) to take two sets of eight images of the sky on an early Martian morning last month. For one set, the camera pointed nearly straight up. For the other, it pointed just above the southern horizon. Cloud movement was recorded in both and was made easier to see by image enhancement. A midday look at the sky with the same camera the same day showed no clouds. (…)
“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.” [More at link]