Currently, a planet-wide dust storm is encircling Mars, blotting out the sky over the two NASA rovers that are currently exploring the Red Planet. The storm is particularly troublesome for the 15-year-old Opportunity rover, which has no power source save its solar panels. Under the darkened skies, the rover has entered a power fault mode, and though NASA was optimistic that the robot could ride out the storm a month ago, the agency has of yet failed to establish contact with Opportunity.
These types of global dust storms kick up on Mars about every 10 years, though the exact cause remains a mystery. However, a new study in Nature Communications reveals that practically all of the dust on Mars comes from one specific rock formation: the Medusae Fossae Formation (MFF).
“The Medusae Fossae Formation has been eroding for the last 3 billion years and is most likely the largest source of Martian dust,” Lujendra Ojha, a postdoctoral researcher at Johns Hopkins University and lead author of the new paper, told Popular Mechanics in an email. “This is similar to Bodele Depression in Chad, which is regarded as the largest single source of dust on Earth.”
More than 3 billion years ago, a massive volcanic eruption is thought to have shaken Mars, ejecting rock, dust, gas, and volcanic ash high into the Martian skies. The eruption was of such a scale that it could have spewed out enough water to cover the entire planet in 4 inches of liquid.
Resent research shows that the volcanic ash and dust settled to form the Medusae Fossae Formation that we see today. This expansive series of trenches, mesas, and ridges (known as yardangs) covers an area equivalent to about 20 percent of the continental United States, making it the largest known explosive volcanic deposit in the solar system. Three billion years ago, it was more than twice that size, stretching over an area closer to 50 percent of the lower 48.
Over the eons, the Medusae Fossae Formation steadily eroded as winds swept over the soft red sedimentary rock. Although Mars does not have many of the eroding processes that create dust on Earth, such as running water and migrating glaciers, the MFF is so lightly held together that it can be broken down by the light Martian breeze. According to the new study, this country-sized deposit of volcanic ash and rock released the vast majority of dust present on Mars today.
“Our calculation suggests that the amount of dust sourced from the MFF is similar to the known volume of dust on Mars,” Ojha says. This dust circulates freely across the planet, and there is enough of it—between 300,000 and 1,800,000 cubic kilometers—to cover the planet in 2 to 12 meters of dust. For reference, the largest building in the world by volume, Boeing’s Everett Factory, is only about .013 cubic kilometers, so you would need about 22.4 million of them to hold all the dust released by the MFF (assuming the lowest estimate). Some dust on Mars has likely been contributed by other sources, but nearly all of it appears to have come from the MFF.
Looking at data from multiple Mars landers and rovers, the team found that dust across Mars has the same abundance of sulfur and chlorine. The ratio of these two chemical elements in the dust is also common across Martian dust. Compositional data from the Mars Odyssey spacecraft, which has been orbiting Mars since 2001, showed that the MFF has the same abundance and ratio of sulfur and chlorine as dust found all over the planet.
On Earth, dust can be trapped in geologic conditions known as sinks that bury the material to form new sedimentary rock. While this process also occurs on Mars, it does not pull nearly as much dust out of the environment. “As long as the flux into sinks in the system (perhaps dusty areas of the planet that never experience strong winds, and so act as permanent dust traps) is less than the erosion out of the MFF, Mars will stay dusty,” Kevin Lewis, an assistant professor of planetary science and co-author of the new study, told Popular Mechanics in an email.
Although the source of the tons and tons of dust on Mars appears to have been revealed, the cause of the planet-engulfing dust storms is still unknown. “The MFF doesn’t cause the dust storms directly (typically they are initiated at other specific locations on the planet), but it seems like the planet has evolved to a critical level of dustiness (in large part due to the erosion of the MFF) that has enabled these runaway dust storms,” Lewis says.
A localized dust storm occurs on Mars about every Martian year, or roughly two Earth years, as the Red Planet makes its closest approach to the sun. The planet-wide storms that occur about every decade have some sort of mechanism that kicks the dust into overdrive, causing it to travel higher into the atmosphere.
Scientists are still working to determine how exactly these global dust events occur, but for now, the source of all that red dust has been identified, adding another piece to the puzzle.
Previously published by: Popular Mechanics USA