Perseverance Sees Drifting Clouds on Mars

NASA’s Perseverance rover mission provided a bluish pre-sunrise gift above Jezero Crater on March 18, 2022, aka Sol 738, or the 738^th Martian day of the mission, with “sol” being the official timekeeping method for Mars missions since one Martian day is approximately 40 minutes longer than one Earth day. And, on this particular sol, the car-sized explorer used one of its navigation cameras (Navcam) to snap images of high-altitude clouds drifting in the Martian sky, which it shared on its officially Twitter page on March 23, 2023.

“This is the time of maximum cloud development in the equatorial and mid-latitudes of Mars, between the northern spring equinox and the summer solstice,” Dr. Agustín Sánchez-Lavega, a Professor of Applied Physics at the Bilbao School of Engineering (University of the Basque Country/Euskal Herriko Unibertsitatea UPV/EHU), recently told Universe Today. “Most of the Martian clouds are formed by ice crystals with sizes between 1 and 4 microns and usually form up to 40 km high. These morning clouds observed by Perseverance are of this nature. In addition, carbon dioxide clouds can also form, which are rarer and require very low temperature conditions. The formation and dissipation cycles of these clouds are important as tracers of the amount of water in the atmosphere and of the dynamical processes that take place in it.”

Scientists involved in Mars missions from both NASA and the European Space Agency have a long history of studying Martian cloud formations, even though the Red Planet is primarily known for its dust storms. Images of Martian clouds go as far back as NASA’s Viking Orbiter 1, when it imaged water ice clouds in the Valles Marineris region on August 17, 1976 during local Mars morning time. NASA’s Mars Pathfinder lander also snapped numerous images of Martian clouds throughout its mission in 1996, which lasted 83 sols, or 85 Earth days. Later Mars missions such as NASA’s Curiosity rover also imaged Martian clouds in 2021, as well.

As noted, clouds on Mars are made of water ice, but they can also possess carbon dioxide (CO2) ice particles, as well. On Earth, water is heated by the Sun which then rises in the atmosphere and condenses to form clouds. Since water is almost non-existent in the Martian atmosphere, the Sun heats the dust-filled air, which then rises and forms clouds. What makes the clouds on both worlds look similar is the texture patterns that give them a sand-like appearance, which is caused by “closed-cell convection” and occurs on Venus, as well.

Dust also plays a role in Martian sunrises and sunsets. While a number of these images, specifically the most recent one from Perseverance, could be mistaken for Earth, what gives Mars away is the blue sunrise color, whereas on Earth sunrises and sunsets are both red. This blue color comes from atmospheric dust and dust particles that cause blue and green colors to scatter more in the Martian atmosphere, whereas red is the most scattered color within Earth’s atmosphere. Much like past images of Martian clouds, Mars missions also have a rich history of snapping beautiful Martian sunsets, as well.

Billions of years ago, when Mars had much more water, the clouds, sunrises, and sunsets quite possibly had a more Earth-like appearance. Unfortunately, as the interior of Mars cooled, the volcanism and protective magnetic field began to dissipate, which caused the water to evaporate to space. Today, Mars is a cold, dry, and dead world, but that doesn’t stop it from trying to share some resemblance to Earth, which makes the recent images taken by Perseverance all the more breathtaking.

How many more breathtaking images of Martian clouds, sunrises, and sunsets will we take, and what new discoveries will scientists make about Martian clouds in the coming years and decades? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!