Massive dust storms on Mars triggered by thermal imbalances, scientists say

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The dust storms engulfing the planet of Mars are driven by a dramatic energy imbalance between seasons and even between day and night on the Red Planet, according to new research.

“One of the most interesting findings is that excess energy – more energy absorbed than produced – could be one of the mechanisms that generate dust storms on March“, said Ellen Creecy in a statement. Creecy is a doctoral student at the University of Houston and lead author of the new research.

Mars is famous for its dust storms, which tend to erupt during the summer in the planet’s southern hemisphere. Often they can expand to encompass a significant region of the Red Planet. For example, in January 2022a dust storm covering almost twice the area of ​​the United States has forced some of NASA’s Mars missions to be extinct until the storm passes. A global dust storm also put an end to the agency’s activity. Opportunity rover in 2018.

Related: A giant pile of dust from Mars is wind-sculpted in this photo by a European probe

Planetary scientists have long wondered where the energy for these vast storms comes from. Solar heating clearly has something to do with it, given the link between dust storms and the austral summer, but the extreme nature of the storms suggests it’s more complex.

Now new research, based mostly on observations from the now defunct NASA Mars Global Surveyor (MGS), which operated from 1996 to 2006, and its thermal emission spectrometer. The scientists also integrated new measurements of the surface temperature of the Curiosity Rover and the InSight Lander, which still work today. Altogether, the researchers found that dust storms are strongly linked to the imbalance between the amount of solar energy absorbed by Mars and the amount of energy it then retransmits as heat.

In technical parlance, this relationship between absorption and re-radiation of heat is called the radiant energy balance. It is different for each planet. The gas giant planets — Jupiter, Saturn and so on – have a great imbalance because their great distance from the sun means they receive relatively little solar energy, but they re-radiate a lot because they still have substantial amounts of interior heat left over from their formation .

A comparison image, showing how a dust storm invaded the Red Planet in 2001. (Image credit: NASA/JPL–Caltech/MSSS)

Earth, on the other hand, has a slight imbalance of between 0.2% and 0.4%, meaning that the amount of heat absorbed by the planet and the amount it radiates back into space are about the same. same. This is partly due to the ability of our oceans and atmosphere to trap and redistribute heat around the planet.

The prevailing hypothesis was that Mars also had a slight disequilibrium, but the new work shows that this is not the case, which can lead to stark differences between the two hemispheres, especially during the austral summer and winter. North.

In 2001, a global dust storm engulfed Mars and MGS was on hand to study the storm in detail. The spacecraft found that during this great storm, there was an energy imbalance between the northern and southern hemispheres of the Red Planet of 15.3%. The extra energy absorbed by the southern hemisphere was more than enough to power the massive dust storms.

Moreover, the imbalance between day and night is even more striking. During the dust storm of 2001, the global average heat emitted decreased by 22% compared to the global average (111.7 watts per square meter) during the day, but increased by 29% at night. The presence of heat-absorbing dust suspended in the atmosphere during the storm is partly responsible for this imbalance, but the main cause is the absence of large oceans or a thick atmosphere, the researchers said.

Artist’s impression of an approaching dust storm on Mars. (Image credit: James Gitlin (STScI))

“Mars is not a planet that has real energy storage mechanisms like we have on Earth,” Creecy said. “Our great oceans, for example, help balance the climate system.”

Once upon a time, Mars had oceans and a thicker atmosphere itself, but the the oceans have dried up more than 3 billion years ago and the atmosphere was mostly lost in space. This story implies that the energy imbalance – and the dust storms it brings – are the product of climate change on Mars. Therefore, Mars can provide a glimpse of what awaits Earth, either in the event of a runaway global warming sets in, or about a billion years in the future when an aging sun will have become too hot for oceans to exist on our planet.

Meanwhile, on Mars, the dust storm season will intensify again in the coming months, with the Red Planet’s southern hemisphere passing its vernal equinox in February 2022, according to the Planetary Society. That means there’s no respite from the dust for the various rovers and landers on the Martian surface – at least until the next austral winter in 2023.

The research is described in a paper published on May 16 in the journal Proceedings of the National Academy of Sciences.

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