Since the dawn of human [observation of Mars](https://www.bgr.com/science/james-webbs-first-photo-of-mars-reveals-new-data-about-the-red-planet/), the presence of nighttime ice clouds on the Red Planet has been recognized, mainly through daylight observations and advanced climate models. Twilight images captured by NASA’s rovers and laboratory climate simulations suggested the presence of delicate wisps of water-ice crystals above the planet’s frigid surface. Nevertheless, effectively demonstrating the true nature of these clouds at night posed a significant challenge for an extended period. This situation was transformed by the Emirates Mars Infrared Spectrometer (EMIRS). A recent study, released in August 2025 in the [Journal of Geophysical Research: Planets](https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025JE008961), clarifies what the EMIRS, located on the HOPE probe, revealed, as well as its implications for upcoming Mars investigations.
The probe and its spectrometer offered the first extensive view of the Martian night clouds. The application of the infrared spectrometer disclosed what was concealed in the darkness, allowing long-standing simulations to be converted into direct, verifiable observations. This accomplishment represents a pivotal advancement in planetary science, inching us closer to comprehending the atmosphere and the water cycles present on the Red Planet.
### The EMIR Mission
When the Emirates Mars Mission’s Hope probe entered orbit around Mars in February 2021, it bore a promise to deliver the scientific community the most comprehensive depiction of [the Martian weather](https://www.bgr.com/science/perseverance-just-created-the-first-martian-weather-report/). Earlier spacecraft on similar missions generally concentrated on specific areas or times of day, but Hope was designed to follow a broad elliptical orbit, enabling observations of the planet’s atmosphere across nearly all latitudes, longitudes, and local times. Thanks to this distinctive perspective, Hope successfully observed cloud formation during the Martian night.
In the JGR: Planets study, researchers utilized data collected by the probe’s infrared spectrometer to monitor water-ice clouds over the course of two Martian years (nearly 4 Earth years). They discovered that cloud formation and dissipation on Mars follows a specific rhythm. Unlike on Earth, clouds do not simply fade in and out; they instead follow a cyclical pattern. Clouds generally thicken overnight, reach their peak near dawn, and diminish by midday. As the day progresses towards evening, the clouds rise once more. Although computer models had anticipated this dual crest of cloud activity on Mars, the EMIR confirmed it.
Another noteworthy discovery is that the behavior of Martian clouds varies with the seasons. During aphelion (the cold season), when Mars is farthest from the Sun, an equatorial cloud belt forms. This is the season when morning clouds cluster around the impressive volcanoes in the Tharsis region.
### The significance of identifying Mars’ night clouds
Up to now, [Mars’ climate models](https://www.bgr.com/1943962/glaciers-on-mars-surface-might-not-be-what-we-thought/) have been based on simulations that could only estimate cloud behavior at night. The Hope probe provided direct measurements, offering scientists the chance to refine those models. Researchers emphasize that this will aid in understanding how energy and moisture travel through the Martian atmosphere, both on a daily and seasonal basis.
Scientists underline that Martian clouds are crucial in maintaining the planet’s thermal equilibrium. Their capacity to either trap or scatter infrared radiation directly influences how heat is distributed between the day and night sides of the planet. With the data from Hope, atmospheric scientists can now quantify these impacts with significantly improved accuracy. This positions the mission’s findings as foundational for grasping the broader Martian climate system. By validating the existence of long-suspected nighttime clouds on Mars, the Hope probe has opened a new avenue for studying the weather patterns of the Red Planet. The years of theoretical investigation have evolved into confirmed knowledge that will steer the next wave of Martian exploration.
