At the end of 2020, planetary scientist Marek Slipski found himself glued to his computer, spending countless hours—more than he’d like to admit, he says—poring over image after image of the Martian atmosphere: zooming in, adjusting the contrast, upping the brightness, and playing around with color. Slipski, a postdoctoral researcher at NASA’s Jet Propulsion Laboratory (JPL), was looking for clouds. Although he’d written up an algorithm for the task, it was yielding mixed results, so he’d resorted to eyeballing the data instead.

But this quickly became overwhelming. Even in the small chunk of data Slipski was studying, there were so many distinct cloud populations, each varying in height and brightness. “After I did this for a week, I was like: ‘Okay, this is going to take a bit more time,’” he recalls. “And it’d be nice to have some help.”

Serendipitously, NASA had just put out a call for its Citizen Science Seed Funding Program, which gives space fans an opportunity to get involved in cutting-edge research. Slipski and Armin Kleinböhl, an atmospheric physicist at JPL, immediately started crafting a proposal. Perhaps the crowd could tackle what Slipski had mostly been attempting to do alone: identify mesospheric clouds. These float at altitudes between 50 and 80 kilometers from the surface, and can be seen in data from the Mars Climate Sounder, an instrument orbiting the planet to measure its atmospheric temperature, ice, and dust content. “We actually got selected as the only planetary proposal,” Kleinböhl says. “I guess the stars aligned—or the planets did!”

After weeks of beta testing, in late June the Cloudspotting on Mars project launched on the Zooniverse, a platform that hosts hundreds of citizen projects. So far about 2,600 volunteers have joined the effort, introducing themselves on the forums (“I am ready to chase the clouds,” a mechanic from France wrote) and digging into the climate sounder’s maps of the atmosphere at different heights, locations, and times of day. Participants need only a computer and internet access to contribute, since the data is viewed using a browser-embedded visualization tool that comes with a quick, optional tutorial.

The five researchers making up the Cloudspotting team hope that this work will shed light on the Red Planet’s global weather patterns and why its atmosphere is so thin compared to our own, and even help them understand how liquid water, once present on Mars’ surface, escaped into space. “The climatology that we will get through the citizen science project will be a lot more comprehensive than what has been in the literature so far,” says Kleinböhl, the sounder’s deputy principal investigator.

He’s particularly interested in the processes driving the formation of Martian clouds, which are composed of either carbon dioxide (dry ice) or water ice. “The CO₂ clouds will tell us something about the structure and dynamics of the atmosphere, and the conditions that lead to very low temperatures,” he says, since carbon dioxide condenses at a temperature typically colder than that of the Martian atmosphere, “while the water ice clouds might tell us something about the presence of water vapor and the processes that might be responsible for transporting water vapor to these high altitudes.”