The Giants of Mars
To understand the climate of Mars, you first need to appreciate its geography, which is dominated by continent-sized scars of its ancient past. The two most significant are the Hellas and Argyre basins in the southern hemisphere. These are not mere craters;
they are gargantuan impact sites from billions of years ago. Hellas Planitia is about 2,300 kilometres across and over 7 kilometres deep—so vast and deep that the atmospheric pressure at its floor is significantly higher than on the surrounding plains. Argyre is smaller but still a huge feature. These basins are so large they create their own weather systems, acting as natural laboratories for studying how topography influences a planet's atmosphere.
A Planet of Extremes
The Martian climate is defined by brutal temperature changes. Because its atmosphere is about 100 times thinner than Earth's, it cannot effectively trap and redistribute heat. This leads to a surface that heats up quickly under the sun and loses that heat just as fast after sunset. Research by Indian scientists from the Physical Research Laboratory (PRL) in Ahmedabad has quantified these swings, recording temperatures ranging from a relatively mild 27 degrees Celsius in summer to a frigid -113 degrees Celsius in winter. This is further complicated by Mars's elliptical orbit, which makes southern summers particularly intense compared to those in the north.
India's Eye on Martian Weather
In a significant advancement for planetary science, the team from PRL used data from the Emirates Mars Mission's Hope spacecraft to create a detailed map of these thermal behaviours. Publishing their work in the journal Current Science, the scientists analysed observations from an infrared spectrometer to look beyond simple temperature readings. This effort builds on India's legacy in Martian exploration, which began with the celebrated Mars Orbiter Mission (Mangalyaan). While Mangalyaan concluded its mission, Indian researchers continue to play a pivotal role in analysing planetary data from various international missions, solidifying the nation's position at the forefront of space science.
Decoding the Zonal Waves
The study revealed that Martian temperatures don't just rise and fall; they move across the planet in large, structured patterns known as zonal waves. Think of them as atmospheric ripples that provide an indirect window into how the thin air circulates across the planet. By tracking these thermal waves, scientists can understand deeper atmospheric currents without directly measuring them. The PRL team discovered a striking difference between the two basins: Argyre was dominated by a large, simple wave pattern (wave-1), while Hellas exhibited more complex and shifting patterns (wave-2 and wave-3) depending on the season.
How the Basins Drive the Climate
The immense depth and unique topography of Hellas and Argyre are the engines driving these waves. During the intense southern summer, the deep columns of air trapped within these basins are heated differently than the surrounding highlands. This temperature and pressure differential generates massive atmospheric waves that propagate across the globe, influencing weather patterns far beyond the basins themselves. The complex wave patterns in the deeper and larger Hellas basin suggest its topography has a more intricate effect on the atmosphere. The findings also help refine existing climate models, as the observed temperatures were often about 10 Kelvin warmer than what models had predicted, highlighting the importance of real-world observation.
