As Mars approaches the southern summer solstice, scientists and spacecraft are preparing for a new season of dust storms, powerful wind-driven dust clouds that can cover thousands of square miles or even whole planet.
For more information on what causes dust storms MartSpace.com spoke with Claire Newman, an atmospheric scientist at Aeolis Research and lead author of a new study that explores how dust devils and winds can fill Martian atmospheres with dust.
Related: Scientists find massive Mars dust storms caused by heat imbalances
Space.com: How much do we know about how dust storms start?
Newman: I could talk for hours about dust storms! One of the big questions we have about Mars is how big dust storms start and we can never predict them. To answer them, one of the really useful things we need to know is how to get the dust off the surface in the first place. Another important thing to know is how much dust is on the surface to be lifted. We can understand processes very well, but if we don’t really know how much dust there is in a particular place, it’s very difficult to accurately estimate it. Then the third thing you need is to have a weather model that describes the environmental conditions. There may be certain types of atmospheric waves or pressure patterns that can cause Mars to be predisposed to a certain type of dust storm.
Space.com: What do the models tell us?
Newman: I posted one paper (opens in new tab) with my colleague Mark Richardson in 2015, where we modeled dust storms but with a limited amount of dust. We found that places that had the strongest winds never held back enough dust to actually produce many dust storms. But in places that produced an average amount of wind, there was dust coming and going from them, because it had enough time to reposition itself and then get up.
Then, there were some interesting things, such as that a region could be completely dust-free during a storm, and then it could not produce the same storm the following year because there would be no dust, and it could take three. years for the dust to build up again and this wind pattern to repeat itself. Then you have to consider the maximum point of the winds due to the seasonal effects and the shape of the earth: where the mountains are, where the slopes are, where the glacial caps are. There is also the possibility of wind variability, whether it is repeated exactly from one year to the next. There is this idea that the system is a bit chaotic, because a small difference could cause a lot of feedback.
When a global dust storm engulfed the Curiosity rover in 2018, it saw dust steadily reduce visibility (image credit: NASA / JPL-Caltech)
Space.com: But is the dust storm season unpredictable to some extent?
Newman: Yes, there is usually a very repeatable storm track, and there are certain smaller storms that appear in certain places at certain times of the year. But big storms don’t usually seem to happen at the exact same time. So in a way, I think we have an idea of when storms can occur and how they can be, but there can be differences. For example, one year a storm could travel south, and the next year not because it is blocked by a combination of pressure patterns. And the next year, 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 them in many different ways. But there is a lot of information we don’t have yet.
Space.com: Is there any resemblance between dust storms in the desert regions of Earth and dust storms on Mars?
Newman: Mars has some big differences compared to Earth: It has a much finer atmosphere, is colder and has a lower one gravity. So Mars is a great way to try to test our theories about dust lifting and sand movement, because we have a lot of theory-based ideas and decades of research in wind tunnels and fieldwork that they are taking place in the deserts of the Earth.
And it’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 how much dust rises; it limits the size of dust storms and prevents global storms from developing, as it is clear that there is no dust to rise over oceans and lakes or places with more vegetation. On Mars, is water still a factor, or is it? so little water which has no effect?
Water on Mars: Exploration and Evidence
Claire Newman (image credit: Claire Newman)
Space.com: How Dust Comes In atmosphere of Mars Does it affect the planet’s climate?
Newman: When there is dust in the atmosphere, it absorbs heat the sun. Because Mars has a very thin atmosphere, a hundred times less dense than Earth, usually most of the solar radiation that reaches the surface is reflected back into space without being absorbed. But when you put 10 times more dust into the atmosphere, it absorbs a lot more solar radiation. This ends up warming the average atmosphere, about 25 miles [16 miles] high, where you could reach 40 degrees Celsius [72-degree-Fahrenheit] increases, while on the surface, the temperature will drop because the dust is absorbing sunlight. Then, at night, the surface cools faster than the atmosphere, and as it gets warmer, the atmosphere begins to heat up the surface below. And there are huge temperature gradients that drive winds and thermal tides that disrupt air circulation, especially during a global dust storm.
Space.com: Is there a connection between dust storms and Mars loses its water in space?
Newman: There are some interesting questions about dust storms and the rate of water loss. During the 2018 global [Mars] storm, there was a large increase in water rising to higher altitudes. A dust storm causes an increase in the vertical speed of the wind and, consequently, in the height reached by the dust, and this can allow more water vapor to be transported higher because it is hotter and there are also higher upward currents. Thus, dust storms have a major impact on water loss rates.
Space.com: Can Dust Warming the Atmosphere Danger to Spaceships?
Newman: As the dust warms the atmosphere, the atmosphere inflates upward, which should be taken into account if you are trying to air brake a spacecraft before entering, descending, and landing. You have to worry about the density of the air and the strength of the wind, and all that stuff. If we understand these things better, we can warn before there are dust storms. Also, by measuring the air pressure at different landing sites, we can get an idea of when the thermal tides are rising. And that’s because there’s a lot of dust in the atmosphere, so we can warn you soon. If there are astronauts on the surface, it would be great if they could have this information to protect themselves.
Follow Keith Cooper on Twitter @ 21stCenturySETI. follow us on Twitter @Spacedotcom (opens in a new tab) and on Facebook (opens in a new tab).