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Where Mars dust comes from



Part of the Medusae Fossae Formation on Mars shows the effect of billions of years of erosion. The image was taken by the HiRISE camera (High Resolution Imaging Science Experiment) aboard the Mars Reconnaissance Orbiter. Credit: NASA / JPL / University of Arizona

The dust that covers much of the surface of Mars comes largely from a single thousand kilometer long geological formation near the equator of the Red Planet, scientists found.

A study published in the journal Nature Communications found a chemical match between dust in the Martian atmosphere and the surface feature, the so-called Medusae Fossae Formation.

"Mars would not be nearly as dusty if it were not for this one huge deposit that gradually erodes over time and essentially pollutes the planet," said co-author Kevin Lewis, an assistant professor of Earth and planetary science Johns Hopkins University.

In the movie The Martian, a dust storm leads to a series of events that plays an astronaut by actor Matt Damon. As in the movie, Dust on Mars has caused problems with real missions, including the explorer-rover Spirit Mars. The fine, powdery stuff can get into expensive instruments and opaque solar panels, which are needed to drive devices.

On earth, dust is separated from soft rock formations by forces of nature such as wind, water, glaciers, volcanoes and meteorite impacts. However, for more than 4 billion years, water currents and moving glaciers have probably made only a small contribution to the global dust reservoir on Mars. While meteorite craters on the fourth planet are a common feature of the Sun, the fragments created by the impacts are typically larger than the fine particles that make up the mire dust.

"How does Mars pollute so much because none of these processes take place? Are active on Mars?" Said lead author Lujendra Ojha, a postdoctoral fellow in Lewis's lab. Although these factors have played a role in the past, something else is responsible for the large dust clouds surrounding Mars, he said.

Ojha and the science team investigated the chemical composition of the dust. Lander and Rover far apart on the planet have all reported surprisingly similar data on the dust. "Dust everywhere on the planet is enriched with sulfur and chlorine and has a very pronounced sulfur to chlorine ratio," said Ojha.

They also looked at data taken from the spacecraft Mars Odyssey, which has been orbiting the planet since 2001

. Ojha and his colleagues found that the MFR region has an abundance of sulfur and chlorine and that the ratio of sulfur to chlorine in the mire dust is right.

Previous results indicate that the MFF was of volcanic origin. Once 50 percent of the continental United States in size, the wind has eroded it, leaving behind an area that is now more like about 20 percent. Yet it is 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 in the last 3 billion years, scientists could approach the current amount of dust on Mars, enough to form a 2 to 12 meter thick global layer.

Dust particles can also affect Mars climate by absorbing solar radiation, which leads to lower temperatures on the ground and higher temperatures in the atmosphere. This temperature contrast can create stronger winds, which causes more dust to be lifted off the surface.

During each Martian year, seasonal dust storms happen (twice as long as one Earth year), global dust storms may emerge about every 10 years

"It explains, possibly, a large chunk of how Mars came to its current state," said Lewis.


Further information:
Image: Mars Dust Storm

Further information:
Lujendra Ojha et al., The Medusae Fossae Formation as the Largest Dust Source on Mars, Nature Communications (2018). DOI: 10.1038 / s41467-018-05291-5

Source:
Nature communications

Provided by:
Johns Hopkins University


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