Mars’ dust primarily spews from 1,000km-long reservoir, study finds
Image credit: nasa
Martian dust largely originates from a single 1,000km-long geological formation near the Red Planet’s equator, according to new research.
“Mars wouldn’t be nearly this dusty if it wasn’t for this one enormous deposit that is gradually eroding over time and polluting the planet, essentially,” said Kevin Lewis, a Johns Hopkins University assistant professor, who co-authored the study.
On Earth, dust is separated from soft-rock formations by forces of nature, including wind, water, glaciers, volcanoes and meteor impacts.
For more than four billion years, however, streams of water and moving glaciers have likely made only a small contribution to the global dust reservoir on Mars, which is called the Medusae Fossae Formation (MFF).
While meteor craters are a common feature on the Red Planet, the fragments created by the impacts are typically bigger than the fine particles that comprise Martian dust.
“How does Mars make so much dust, because none of these processes are active on Mars?” said the study’s lead author Lujendra Ojha.
Although these factors may have played a role in the past, something else is to blame for the large swathes of dust surrounding Mars now, he said.
Ojha and the science team looked at the dust’s chemical composition. Landers and rovers far apart on the planet have all reported surprisingly similar data about the dust. “Dust everywhere on the planet is enriched in sulphur and chlorine and it has this very distinct sulphur-to-chlorine ratio,” Ojha said.
They also studied data captured by the spacecraft Mars Odyssey, which has orbited the planet since 2001. Ojha and his colleagues were able to pinpoint the MFF region as having an abundance of sulphur and chlorine, as well as a match to the ratio of sulphur to chlorine in Mars dust.
Earlier findings suggest that the MFF had a volcanic origin. Once 50 per cent of the continental United States in size, the wind has eroded this down to just 20 per cent, although it is still the largest known volcanic deposit in our solar system.
Wind-carved ridges known as yardangs are the remnants of erosion. By calculating how much of the MFF has been lost over the past three billion years, the scientists could approximate the current quantity of dust on Mars, enough to form a 2-12 metre-thick global layer.
Dust particles can also affect Martian climate by absorbing solar radiation, resulting in lower temperatures at the ground level and higher ones in the atmosphere. This temperature contrast can create stronger winds, leading to more dust being lifted from the surface.
The planet has recently been embroiled in a global dust storm lasting for weeks that has blocked out the Sun causing Nasa’s opportunity rover to lose power.
While seasonal dust storms happen every Martian year (twice as long as an Earth year), global dust storms can form about every 10 or so years.
“It just explains, potentially, one big piece of how Mars got to its current state,” Lewis said.
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