Scientists trace origin of Martian dust

Similar composition of dust grains around the planet lead researchers to single source.
By Laurel Kornfeld | Sep 26, 2018
Mars's abundant dust comes from one geological formation near the planet's equator, a 621-mile (1,000-km) region that has undergone billions of years of erosion and may have once been volcanic.

Known as the Medussae Fossae Formation, this large deposit, which continues to erode over time, has been imaged by the HiRISE camera on NASA's Mars Reconnaissance Orbiter (MRO).

Unlike dust on Earth, which is separated from rock by water, wind, glaciers, volcanoes, and even meteor impacts, dust on Mars has experienced little influence from any of these phenomena. Ancient surface water and moving glaciers had a limited impact on the dust's movement.

With a much thinner atmosphere than that protecting Earth, Mars experiences more meteor impacts than our planet, but fragments created by meteors are significantly larger than the fine, tiny Martian dust grains.

Led by Lujendra Ojha and Kevin Lewis of Johns Hopkins University, a team of researchers studied the chemical composition of dust grains collected by landers and rovers in various locations on the Red Planet and found a distinct similarity in all the samples.

"Dust everywhere on the planet is enriched in sulfur and chlorine, and it has this very distinct sulfur-to-chlorine ratio," Ojha noted.

NASA's Mars Odyssey, which has been orbiting the planet since 2001, found the dust in the Medusae Fossae Formation to have the same abundance and ratio of sulfur and chlorine as the dust studied by the rovers and landers.

"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," Lewis stated.

The Medussae Fossae Formation is the largest known volcanic deposit in the solar system though it has been steadily shrinking due to erosion by the Martian wind.

By measuring the ridges carved by the wind over time, scientists can calculate how much of the region's dust has eroded over three billion years, enabling them to approximate the current amount of dust on the Red Planet capable of forming a global layer between 6.6 and 39 feet (2-12 meters) thick.

Dust particles can lower ground temperatures on the Martian surface and raise them further up in the atmosphere through absorption of solar radiation. Greater discrepancy between ground and atmospheric temperatures causes stronger winds, which pick up and transport surface dust.

Every few years, regular seasonal dust storms can become global, potentially harming science instruments and their solar panels by getting stuck inside both.

Findings of the study have been published in the journal Nature Communications.

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