In the south of Mars, summer begins on July 21. For scientists, that means another complex dusty season.
Mars weather is dusty especially in the spring and summer in the southern Hemisphere, when warmer temperatures create stronger winds that stir up the surface. Road-to-road air poles, known as dust Devils, are also very common, pushing dust higher into the atmosphere, where it can remain suspended for days. The most extreme storms occur every few years and cover the entire planet in a thick layer of smoke for months.
Why is there so much dust?
Scientists are still uncertain about the cause of these dusty storms. However, in a recent study, researchers pointed out that Mars experienced a large energy imbalance at the same time as major dusty storms developed. The results show that the red planet absorbs up to 15% more solar energy than the heat energy it emits back into space in the spring in the south and this excess energy continues in the summer.
Ellen Creecy, an atmospheric scientist at the University of Houston and lead author of the study, said Mars experiences intense changes in the amount of solar radiation as it rotates around the Sun.
This is because Mars' orbit is elip, meaning the planet is much closer to the sun in spring and summer in the south, when it receives more solar radiation. But researchers found that the amount of solar energy emitted was barely increasing.
According to Liming Li - a planetary scientist at the University of Houston - the increase in emitted power cannot be compared to the increase in solar radiation.
In turn, excess energy will warm the atmosphere near the surface and promote the air to fly, leading to dust storms. But whether the seasonal imbalance is linked to dusty storms across the Red planet such as the most recent match covering the planet in 2018 remains an open question. Creecy says the energy imbalance is affecting the entire climate system, so it could play a role.
Tracking
Mars' summer is also the time when people find dark streaks on the dusty surface of the red planet. These recurring slopes ( RSL) develop gradually over a period of months, then fade away or disappear. The cause of RSL spots is still unknown, but some believe they are caused by dust storms.
In fact, planetary scientist Alfred McEwen at the University of Arizona (USA) in a study published in 2021 found more RSLs after a dusty storm in 2018.
RSL are largely driven by attraction, but they need something to get them away. The results show that dust storms, including dust Devils, could be such a catalyst.
In addition, the 2018 storm that built up dust on much of Mars' surface is likely to explain why traces have faded or disappeared over time. McEwen added that the difference in the amount of dust could explain why they are present on some mountainsides, not others.
In the future, researchers hope to study the locations where these global storms began to see if there was an energy imbalance there. Future observations of RSL and studies of energy balance at specific locations could help uncover the mysteries of Mars dusty summer. Meanwhile, the dusty season will continue until December 26, the beginning of autumn in the south of Mars.
