While clouds exist on Mars, they aren't as common an occurrence as they are here on Earth owing to the thin and dry atmosphere encircling the Red Planet. NASA's Curiosity rover has captured a rare perspective of them at an unexpected time and location, which will help scientists better understand the reasons behind their formation.
Clouds can usually be found during the coldest time of the Martian year at the planet's equator, but two years ago, or one Martian year, NASA scientists spotted them forming earlier than usual. This time around the team had the necessary pieces in place to capture these uncommon cloud formations, with Curiosity's navigation and mast cameras snapping a series of black and white and color photographs as they moved across the Martian sky.
These show "wispy puffs" packed with ice crystals that scatter sunlight and appear to glow against the sky behind them. That they glow brighter as they fill with crystals and then darken as the Sun sets offers scientists an idea of how high these uncommon clouds are.
Already this has led to one interesting discovery, with these early clouds forming at a higher altitude than typical Martian clouds, which hover at altitudes of no more than 37 miles (60 km) and are made of water ice. Because it is much colder where these new clouds have been spotted, the scientists believe they are instead formed of frozen carbon dioxide, or dry ice.
One particularly striking example is the image of colorful "mother of pearl" clouds, seen in this composite image of five frames stitched together.
“If you see a cloud with a shimmery pastel set of colors in it, that’s because the cloud particles are all nearly identical in size,” says Mark Lemmon, an atmospheric scientist with the Space Science Institute in Boulder, Colorado. “That’s usually happening just after the clouds have formed and have all grown at the same rate.”
Further analysis of these images will help scientists determine which clouds are formed of dry ice and which ones are water ice, and inform their broader understanding of how clouds form on the Red Planet.
Source: NASA