NASA’s Curiosity Mars rover captured a short clip of spectacular dry ice clouds illuminated by the Sun as they drifted over the Red Planet. Martian clouds are predominantly composed of dry ice or frozen carbon dioxide, a consequence of the planet’s 95% CO2 atmosphere. These iridescent clouds form only under low temperatures and at high altitudes.
Curiosity has been climbing Mount Sharp—an 18,000-foot-high volcano located in Gale Crater—and has reached a sufficient altitude to witness these phenomena. The clouds are known as noctilucent, or bright night clouds, as they become especially vivid during the Martian twilight. Sometimes they display a rainbow of colors, creating what are called iridescent, or “mother-of-pearl” clouds.
Mark Lemmon, an atmospheric scientist with the Space Science Institute in Boulder, Colorado, shared his experience: “I’ll never forget the first time I saw those iridescent clouds and was sure at first it was some color artifact.
Martian dry ice clouds observed
Now it’s become so predictable that we can plan our shots in advance; the clouds show up at exactly the same time of year.” Lemmon’s research includes a paper detailing the initial observations of noctilucent clouds on Mars.
One intriguing aspect is why carbon dioxide ice clouds have not been observed in other Martian regions. For instance, the Perseverance rover, located in the northern hemisphere’s Jezero Crater, has yet to report such clouds since its 2021 landing. Lemmon hypothesizes that specific Martian regions may be more conducive to their formation.
He suggests that gravity waves, which can cool the atmosphere, could play a role. “Carbon dioxide was not expected to condense into ice here, so something is cooling it to the point that it could happen. But Martian gravity waves are not fully understood, and we’re not entirely sure what is causing twilight clouds to form in one place but not another,” he explained.
The video of these mesmerizing clouds is available on the Physics Insight YouTube channel.
Image Credits: Photo by Planet Volumes on Unsplash
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