As Mars approaches its southern summer solstice, scientists and spacecraft are preparing for a new season of dust storms, powerful wind-driven clouds of dust that can cover thousands of square miles. or even the entire planet.
Learn more about the causes of dust storms MarchSpace.com spoke with Claire Newman, atmospheric scientist at Aeolis Research and lead author of a new study exploring how dust devils and winds can fill the Martian atmosphere with dust.
Related: Massive dust storms on Mars triggered by thermal imbalances, scientists say
Space.com: What do we know about how dust storms start?
new man: I could talk for hours about dust storms! One of the big questions we ask about Mars is how big dust storms start and will we ever be able to predict them. To answer this, one of the really useful things we need to know is how dust is lifted from the surface in the first place. Another important thing to know is how much dust there is on the surface to be lifted. We can understand the processes very well, but if we don’t really know how much dust there is in a particular place, then it’s really hard to be able to estimate it accurately. Then the third thing you need is to have a weather model that describes the environmental conditions. There could be certain types of atmospheric waves or pressure patterns that could make Mars predisposed to have some type of dust storm.
Space.com: What do the models tell us?
new man: I posted a paper (opens in a new tab) with my colleague Mark Richardson in 2015, where we modeled dust storms but with a restricted amount of dust. We found that the places with the strongest winds never held enough dust to really produce a lot of dust storms. But in places that produced an average amount of wind, there was dust blowing in and out of it, because it had enough time to redeposit and then lift.
Then there were interesting things such as an area could be completely dust free during a storm, and then it wouldn’t be able to produce the same storm the following year because there wouldn’t be any dust there. -low – and it could take three years for the dust to build up and the wind patterns to repeat. Then you need to consider where the winds peak due to seasonal effects and the shape of the terrain – where the mountains are, where the slopes are, where the ice caps are. There is also the possibility of variability in the wind, that it repeats itself exactly from year to year. There’s this notion that the system is a bit chaotic, because a small difference could trigger a big comeback.
Space.com: But isn’t dust storm season predictable to some degree?
new man: Yes, there is usually a very repeatable storm track, and there are certain small storms that appear in certain places at certain times of the year. But big storms don’t usually seem to happen at exactly the same time. So in a way I think we have an idea of when the storms might happen and what they might look like, but there may be differences. For example, one year a storm may move south, and the next year it does not because it is blocked by a combination of pressure patterns. And the year after, there could be a different combination that would allow the storm to spread. They are really very difficult to fully understand, and you can attack it in different ways. But there is a lot of information that we don’t have yet.
Space.com: Are there similarities between dust storms in desert regions of Earth and dust storms on Mars?
new man: Mars has big differences from Earth: It has a much thinner atmosphere, it is colder and it has a gravity. So Mars is a great place for us to try and test our theories of dust lifting and sand movement, as we have many ideas based on theory and decades of wind tunnel research and field work. in the deserts of the Earth.
And that’s a good question: Are they the same processes? For example, do electrostatic effects have a greater impact on Mars because Mars is drier? On Earth, water is an extremely important factor in the amount of dust raised; it limits the size of dust storms and prevents global storms from developing, because clearly there is no dust to kick up on oceans and lakes or on places that are more vegetated. On Mars, is water always a factor, or is there so little water that has no effect?
Water on Mars: exploration and evidence
Space.com: How does dust get in? Atmosphere of Mars affect the planet’s climate?
new man: When dust is in the atmosphere, it absorbs heat the sun. Because Mars has a very thin atmosphere, one hundred times less dense than Earth, usually most of the solar radiation that passes through the surface is then reflected back to space without being absorbed. But when you put 10 times more dust in the atmosphere, it absorbs a lot more solar radiation. This ends up heating the middle atmosphere, about 25 kilometers away [16 miles] high, where you might get a temperature of 40 degrees Celsius [72-degree-Fahrenheit] increase, while on the surface, the temperature will drop because the dust absorbs the sunlight. Then, at night, the surface cools faster than the atmosphere, and because it’s warmer, the atmosphere begins to warm the surface below. And there are huge temperature gradients that drive thermal winds and tides that alter atmospheric circulation, especially during a global dust storm.
Space.com: Is there a link between dust storms and Mars loses its water in space?
new man: There are interesting questions about dust storms and water loss rate. During the 2018 global [Mars] storm, there was a large increase in water being elevated at higher elevations. A dust storm causes an increase in the vertical wind speed and, therefore, the height reached by the dust, which can allow more water vapor to be carried higher because it is warmer and there is also larger updrafts. Dust storms therefore have a significant impact on water loss rates.
Space.com: Can the dust that warms the atmosphere pose a danger to spacecraft?
new man: As the dust heats the atmosphere, the atmosphere swells upwards, which needs to be considered if you are trying to aerobrake a spacecraft prior to entry, descent and landing. You have to worry about air density and wind strength, and all of those things. By understanding these things better, we can give early warnings that there may be dust storms. Additionally, by measuring atmospheric pressure at different landing sites, we can get an idea of when thermal tides are rising. And that’s because there’s a lot of dust in the atmosphere, and so we can give an early warning there. If there are astronauts on the surface, it would be nice if they could have that information so they could get to safety.
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