Researchers from Khalifa University have investigated data from the Emirates Mission to Mars to identify patterns in cloud development on Mars. Understanding this process could feed into long-term climatic studies into how Mars lost its atmosphere and whether such a thing could happen here on Earth.
Clouds on Mars fascinate researchers. Mars has a thin atmosphere and water scarcity, so clouds are rare occurrences on the red planet. When they do form, they may not be water-ice clouds at all, but dry ice clouds — so high in the atmosphere and so cold that they’re clouds of frozen carbon dioxide. An infrequent and little understood phenomenon, water-ice clouds are the focus of research for Khalifa University’s Dr. Samuel Atwood, Post-doctoral Fellow.
With researchers from Arizona State University; Northern Arizona University; Space Science Institute, Colorado; Laboratoire de Météorologie Dynamique, France; NASA Goddard Space Flight Center; and Mohammed Bin Rashid Space Center, Dr. Atwood used observations from the Emirates Mars Mission Hope Probe spacecraft to measure the abundance of clouds in the Martian atmosphere and investigate how they change throughout the day. Their results, published in Geophysical Research Letters, add detail to our understanding of cloud behavior on Mars and help validate computer models of the Martian atmosphere.
The Emirates Mars Mission is the United Arab Emirates’ first mission to Mars, its Hope Probe designed to orbit the red planet and study the dynamics in the Martian atmosphere. One of the instruments on board the Hope Probe is the Emirates Mars Infrared Spectrometer, used to study the clouds on Mars.
“A considerable record of Martian water-ice-cloud observations from thermal-infrared spectrometers has now been produced from the combined measurements of numerous Mars missions,” Dr. Mohamed Ramy El-Maarry, Associate Professor and Director of the Space and Planetary Science Center, and co-author on the paper explained. “From these, a general climatology has been developed showing water-ice cloud to be a prominent component of the Martian atmosphere with substantial seasonal and spatial variability.”
This variability is the focus of Dr. Atwood’s research. The Hope Probe orbits Mars at a greater distance than most previous orbiting spacecraft, which are traditionally inserted closer to the planet to get high-resolution pictures and act as telecommunications relay stations for the probes sent to the surface. Instead, the EMM will study the weather and climate systems from a greater distance, which will allow measurements at different times of day and across a larger section of the planet at any one time.
Previous research has shown a pattern of increasing and decreasing cloud coverage throughout the Martian day.
“We know there is a general midday minimum in water-ice-cloud abundance in the aphelion cloud belt, a prominent region of clouds occurring at low latitudes near the equator during the Mars aphelion season when Mars is at its farthest distance from the Sun,” Dr. Atwood said. “This has been observed over six years of data from other instruments orbiting Mars. Some studies indicate that cloud cover increases throughout the day and reaches a maximum in the afternoons, while others show generally higher nighttime water-ice-cloud abundance. However, there are gaps in our observations, which limit our understanding of how these clouds develop and which hinder efforts to develop Martian atmospheric climatologies, validate global circulation models, and resolve observational anomalies.”
Using data gathered from the Emirates Mars Infrared Spectrometer, combined with modelling tools, the research team detailed the daytime cloud variability for different regions on Mars. They considered the aphelion cloud belt, a prominent region of clouds commonly observed near the equator during the Mars cold season, and orographic clouds, which form in the vicinity of volcanoes in response to the forced lifting of air by the surface topography.
The results show that throughout much of the aphelion cloud belt, the lowest optical depths were observed near midday, with higher values often occurring in both the morning and afternoon. Optical-depth measurements provide information on the radiative properties of clouds, helping to determine the liquid and ice-water content as infrared light is scattered. The higher the optical depth, the more water in the cloud. For the orographic clouds at the volcanoes, optical depths increased through the afternoon and showed no indication of a maximum having been reached by dusk when coverage ended for this study.
“The data from the Emirates Mars Mission constitute a new and unique Mars atmospheric data set due in large part to the observational capabilities of the EMM Hope Probe spacecraft,” Dr. El-Maarry said. “The results were generally consistent with expectations based on previous observational datasets and model findings, but the observational coverage provided by the Emirates Mars Infrared Spectrometer allowed for more detailed analysis of the development of water-ice clouds throughout the day, especially in the morning hours when fewer observations have historically taken place.”
Future work using data from the EMM will focus on extending the timeframe for analysis to a full Martian day, particularly during the night. As we learn more about the atmosphere on Mars, we can use data from the EMM to help model the Earth’s atmosphere and study its evolution over millions of years.
24 October 2022