Mars may look like a frozen, lifeless desert, but new observations show that its climate is far more dynamic and structured than a simple cycle of hot days and freezing nights. Researchers from India’s Physical Research Laboratory (PRL) have mapped seasonal, daily and large-scale temperature variations across two of Mars’ biggest impact basins, Hellas and Argyre. Their study, published in the journal Current Science on September 10, uses observations from the Emirates Mars Mission’s Hope spacecraft.
The findings provide new clues about how Mars’ thin atmosphere circulates and how the planet’s enormous surface features influence its weather and climate.
Mars swings between extreme heat and cold
The researchers found extraordinary variations in surface temperature across the studied regions.
Temperatures ranged from roughly -123 degrees Celsius to nearly 22 degrees Celsius. Such dramatic swings are possible partly because Mars has a very thin atmosphere that is inefficient at transporting and retaining heat compared with Earth’s atmosphere.
As a result, the Martian surface can heat rapidly when exposed to sunlight and lose that heat just as quickly after sunset.
The Hope mission is particularly valuable because its orbit allows scientists to observe Mars at different local times and through changing seasons, providing a much broader picture than measurements collected from individual rovers at fixed locations.
Why southern summer gets especially intense
Mars does not orbit the Sun in a perfect circle. Its relatively eccentric orbit means the planet reaches its closest point to the Sun during southern summer.
That orbital geometry makes southern summer particularly intense, with stronger heating in parts of the southern hemisphere than during the corresponding northern season.
The Indian researchers found that temperature behavior across Hellas and Argyre was not controlled by season alone. The data also revealed broad wave-like patterns in temperature, suggesting that atmospheric circulation is leaving a measurable signature on the surface.
Temperature waves reveal Mars’ atmospheric movement
One of the study’s most important findings involves what scientists call zonal wave patterns.
These are large-scale variations in temperature that extend across longitude and can provide indirect information about atmospheric circulation. In effect, researchers can study changes in surface temperature to better understand processes taking place in the atmosphere above it.
The patterns were different in the two impact basins.
Argyre was largely characterized by a wave-1 pattern, meaning one major temperature variation around the basin. Hellas displayed more complicated wave-2 and wave-3 patterns at different times of year.
The researchers linked these differences to the basins’ enormous depths and distinctive topography. Mars’ landscape does not simply sit beneath its atmosphere. It can actively shape atmospheric circulation and temperature patterns.
Hellas and Argyre offer a natural climate laboratory
Hellas is one of the largest impact basins in the solar system, while Argyre is another vast depression in Mars’ southern highlands.
Their size, depth and location make them useful natural laboratories for studying how topography interacts with the Martian atmosphere.
The new observations show that two nearby regions can respond differently to the same seasonal forces. That matters because models of the Martian climate must account not only for solar heating and atmospheric composition, but also for the planet’s highly uneven terrain.
Scientists have long known that Mars experiences planetary-scale waves and atmospheric circulation patterns. The new analysis adds detailed surface-temperature observations that help connect those atmospheric processes with specific geographic features.
Hope spacecraft is giving scientists a wider view
The measurements come from EMIRS, the Emirates Mars Infrared Spectrometer aboard the Hope spacecraft.
EMIRS observes Mars in the infrared and is designed to measure temperature as well as the distribution of dust, water vapor and ice in the lower and middle atmosphere. Hope’s unusual elliptical orbit allows it to observe Mars over much of the planet and at different local times.
That makes the mission particularly useful for studying the planet’s daily temperature cycle, seasonal changes and atmospheric dynamics.
Earlier research using EMIRS had already demonstrated that the instrument could provide temperature measurements covering most of Mars at different local times and could be compared with readings from NASA’s Curiosity and Perseverance rovers.
The latest study takes that capability further by focusing on the complex behavior of two major impact basins.
Mars Climate Database gets the broad pattern right
The researchers also compared their observations with predictions from the Mars Climate Database, a widely used modeling tool for studying Martian atmospheric conditions.
The model reproduced many of the broad temperature patterns detected by EMIRS. However, the researchers found that its predicted temperatures were often lower than the observed values.
That difference is scientifically important because observations can expose where atmospheric models need refinement. Better agreement between models and actual measurements could improve simulations of Martian weather and climate at regional scales.
Such improvements could eventually help mission planners understand environmental conditions faced by spacecraft, landers and future crews.
What this means for future Mars missions
Understanding Mars’ temperature behavior is more than an academic exercise.
Robotic spacecraft and future human missions will need accurate information about surface temperatures, atmospheric circulation, dust and seasonal weather conditions. Climate models can help predict those conditions, but their reliability depends on how well they reproduce what spacecraft actually observe.
The latest PRL study therefore adds another piece to the increasingly detailed picture of Mars as a planet with an active and complicated climate system.
Mars remains cold, dry and inhospitable by terrestrial standards. But beneath that barren appearance is an atmosphere capable of producing waves, circulation patterns and dramatic thermal changes, all strongly influenced by the planet’s seasons and terrain.