A massive dust storm on Mars that threatened a NASA lander is finally fading.
At the end of September, NASA Mars reconnaissance orbiter sounded the alarm for missions studying the red planet: A dust storm was brewing. Such storms have a grim reputation among surface missions since a storm circling the entire planet put an end to solar power. Opportunity rover mission in 2018. And NASA now has another solar-powered robot on the surface to worry about: its InSight Lander. For a few weeks the storm left InSight alone, but by early October dust had darkened the sky above and spacecraft personnel were concerned their mission would come to an abrupt end.
Now it’s clear that although the end of the InSight mission is still looming, the lander is going through the worst of the storm and dust is starting to fall from the sky, Claire Newman, atmospheric scientist at Aeolis Research who works on weather observations from the surface of Mars spacecraft, Space.com told Space.com.
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Scientists are still working to understand the nuances of the Red Planet’s weather, and its dust storms in particular, Newman said. Small local dust storms can occur year-round, but larger storms become more frequent in late summer in the Southern Hemisphere, so a storm like the one that threatened InSight is not not beyond the norm.
“It’s a type of event that we often see at this time of year,” Newman said. “We were hoping it would just be a regional. It looks like that guy is pretty big.”
Storms follow a seasonal pattern because they are triggered by thermal imbalances that lift dust from the surface and into the thin Martian atmosphere. This triggers a vicious circle. “You kick up the dust, the dust heats up, which tends to lower those temperature gradients, so locally you tend to have stronger winds, and then they tend to kick up more dust,” Newman said.
Orbiters can detect brewing storms in images and temperature data, but surface missions can also identify storms, even the most distant ones, because dust makes the typical daily Martian cycle of atmospheric pressure more dramatic. The Rover of Perseverancefor example, detected these pressure changes in the early days of the storm, even without dust in the sky above Jezero Crater.
“It’s a global response to something that might only happen in a third of the planet or even less,” Newman said.
It’s different from a global storm, which fills the atmosphere around the entire planet, from east to west, with dust. These storms can form every few years because on Mars it is difficult to stop the feedback cycle triggered by dust in the atmosphere.
“You don’t get a global-scale dust storm on Earth, and that’s partly because the thick atmosphere kind of prevents these really strong feedbacks,” Newman said. “But it’s also because you have the oceans and you have water and precipitation, and that pulls dust out of the atmosphere, whereas on Mars you don’t have any of that to slow the dust.”
Although the recent storm was a significant regional event, it failed to cover the entire planet. The reprieve may come from the fact that usually at this time of year the surface winds on Mars blow from the north, and this storm started from the south. So while the northern hemisphere’s upper atmosphere (where Perseverance is displayed) became somewhat dusty, the storm itself might have struggled to gain a foothold on the surface and expand northward.
“It could be that the time of year this is happening and the background circulation has made it more difficult for it to expand and go global,” Newman said. “It’s going to struggle to expand northward and into the northern hemisphere at low levels because the background flow is coming from the wrong direction.”
It’s unlikely, but not impossible, that Mars will experience another major dust storm this year, Newman said. “We’re probably coming to the end of the big dust storm season,” she said. “You can never say never with Mars.”
The recent storm is the second major to occur this Earth year, following a storm that occurred near the Perseverance rover outpost in Jezero Crater. This storm came unusually early in the season and was particularly intriguing, Newman noted.
“It was the first time we could take detailed observations in a place where there was active dust lifting during the storm,” she said. “We were actually in a stormy location.”
Previously, other surface missions in places where dust was lifting from the surface had to hunker down, unable to observe the phenomenon. That said, January’s Perseverance sightings didn’t quite go to plan: the storm’s winds were strong enough and carrying enough debris that they damaged one of the rover’s wind sensorshindering the measurements the rover can make.
Fortunately, there was still plenty to see. “When that January storm came over us, we saw a big increase in dust kicking up and even dust devils,” Newman said. “We also saw a lot of movement on the surface; we basically saw little ripples moving around.”
InSight is particularly vulnerable to dust storms due to its reliance on solar panels, but the nuclear power plant Curiosity and Perseverance rovers always benefit from knowing that a storm is approaching.
Scientists can advance activities that would be easier before a storm arrives, for example, or delay activities that could be more dangerous in high winds. And, of course, they can schedule additional sightings of the storm itself. “Even if you don’t have to worry about dust, you still want to agree to do some weather monitoring,” Newman said.
And weather observations, especially on the surface, are crucial for scientists working to develop models of dust storms that better match reality.
“No model can simulate the life cycle of a dust storm really well,” Newman said, unless scientists load them with lots of special specifications. “All models diverge from reality at some point.”
These models are essential for the work she and other atmospheric scientists are doing using surface observations at individual locations in addition to orbital data to reconstruct the dynamics of Mars on a much larger scale than is currently possible. any spacecraft can observe.
“We’re trying to figure out where we are,” she said of the surface weather stations. “We’re trying to understand the whole planet by understanding where we are. And we’re also trying to understand the past by understanding the present.”
Email Meghan Bartels at mbartels@space.com or follow her on Twitter @meghanbartels. Follow us on Twitter @Espacedotcom and on Facebook.
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