Mars' Nights Are Cloudier Than Anyone Expected

[Buster's Uncle]

Mars' Nights Are Cloudier Than Anyone Expected, And Now Scientists Finally Have The Full Picture
Nicolae Bochis
BGR
Tue, September 23, 2025 at 6:17 AM EDT
3 min read



Image of planet Mars from space - Triff/Shutterstock


Since humans first started observing Mars, the existence of nocturnal ice clouds on the Red Planet has been known, primarily through daytime observations and sophisticated climate models. Twilight imagery from NASA's rovers and laboratory climate simulations hinted at wispy formations of water-ice crystallites above the planet's cold surface. However, capturing the true nocturnal character of these clouds remained a challenge for a long time. That changed with the Emirates Mars Infrared Spectrometer (EMIRS). A new study, published in August 2025 in the Journal of Geophysical Research: Planets, explains what exactly the EMIRS, aboard the HOPE probe, captured, as well as its implications for future Mars research.

The probe and its spectrometer allowed us the first comprehensive view of the Martian night clouds. Using the infrared spectrometer revealed what was hidden in the darkness, and long-standing simulations can now be turned into direct, verifiable observations. This achievement marks a milestone in planetary science, bringing us one step closer to understanding the atmosphere and the water cycles on the Red Planet.


The EMIR Mission


A rover on the Mars planet surface - Triff/Shutterstock


When the Emirates Mars Mission's Hope probe slipped into orbit around Mars in February 2021, it carried a promise that it would provide the science world with the most complete picture of what the weather is like on the Red Planet. Previous spacecraft with similar missions typically focused on specific regions or times of the day, but Hope was programmed to follow a sweeping elliptical orbit that allowed it to observe the planet's atmosphere from virtually all latitudes, longitudes, and local times. It's because of this unique vantage point that Hope managed to directly observe the clouds forming in the Martian night.

In the JGR: Planets study, researchers used the data gathered by the probe's infrared spectrometer to track water-ice clouds across two Martian years (almost 4 years on Earth). They found out that there's a certain rhythm to the formation and dissipation of clouds on Mars. Clouds do not simply fade in and out like on Earth. They instead wax and wane in a cycle. Clouds tend to thicken overnight, peak near dawn, and weaken around midday. As the day comes closer to the evening, the clouds rise again. Computer models predicted this double crest of cloud activity on Mars, but the EMIR finally confirmed it.

Another interesting finding is that the Martian clouds change their behavior depending on the season. During aphelion (the cold season), the period when Mars is furthest from the Sun, an equatorial cloud belt emerges. That's the season when morning clouds cluster over the towering volcanoes of the region known as Tharsis.


The importance of finding Mar's night clouds


A picture of Mars from space - Fordelse Stock/Shutterstock


Until now, Mars' climate models relied on simulations that could only approximate how clouds behave during the night. The Hope probe provided direct measurements and offered the scientists an opportunity to refine those models. Scientists note that this will help them understand how energy and moisture circulate through the Martian atmosphere, both daily and seasonally.

Researchers highlight that Martian clouds play a critical role in regulating the planet's thermal balance. Their ability to trap or scatter infrared radiation directly affects how heat is redistributed between the planet's day and night sides. With Hope's data, atmospheric scientists can now quantify those effects with far greater accuracy. This makes the mission's findings a cornerstone for understanding the broader Martian climate system. By confirming the existence of long-suspected night clouds of Mars, the Hope probe opened a new window into the weather of the Red Planet. The decades of theoretical work have transformed into verified knowledge that will guide the next generation of Martian research.

Read the original article on BGR.