Every now and then, the operators of NASA’s Mars Science Laboratory mission Curiosity take a break from avoiding sand traps and analyzing rocks for signs of ancient, habitable environments and instead point the rover’s robotic eyes to the sky to look at the clouds.
That’s what they did last month on July 17th, when early in the Martian morning they pointed Curiosity’s Navigation Camera (Navcam) up to capture two image sequences of feathery clouds as they drifted overhead.
The first clip shows smoky thin clouds moving from left to right as they pass right above the rover. In the second, the camera is aimed to the southern horizon line, revealing how a thin layer of similarly wispy clouds floats above two rounded hills. The Martian clouds shown in the videos look strikingly familiar and Earth-like. According to NASA, these cloud images are the “most clearly visible so far from Curiosity.”
Each sequence is made of eight images taken over a 4-minute time span. They have been processed to adjust for sensitivity differences among pixels in the camera’s sensor and to remove lens artifacts and then creating an “average” of all the frames and subtracting it from each individual frame. These corrections enhance the changes caused by movement and lightning — at the cost of adding some extra grain — making the clouds easier to see. NASA also published a version of the first video without enhancements where the clouds are much less noticeable.
Although the rover’s operators most likely appreciate the change of subject, this is not a leisure activity. Researchers have been observing the Martian sky from the planet’s surface from years, using Curiosity and other previous missions such as the Phoenix Mars Lander, in order to study its climate.
Thanks to these observations as well as others by orbiting spacecraft and the Hubble Space Telescope, scientists have learned much about Mars’s cloud regime, which is driven by the planet’s elliptical orbit. When Mars is closer to the Sun, the extra sunlight it receives heats things up and can create global dust storms that may prevent cloud formation. As it moves away from our star and cools down, clouds begin to form in two major systems: made of frozen carbon dioxide on top of the colder poles and made of water-ice along a wide band following the equator.
These videos show examples of the second type — water-ice cirrus clouds similar to the ones found on Earth.
You can read more about the videos in NASA’s Jet Propulsion Laboratory’s press release.