Most Martian Dust Probably Came From a Single Geological Formation

Mars has a well-deserved reputation as the dustball of our solar system. Currently, a humongous dust storm has completely encircled the planet, and this isn’t the first time. That happens every couple of years. Scientists studying the Martian dust now think they know how it all got there. According to researchers at Johns Hopkins University, most of the dust on Mars came from a single geological formation.

On Earth, outdoor dust forms from any process that breaks up rocks. That could be a volcanic eruption, asteroid impact, or water erosion. Probably the most common, though, is wind erosion. Mars today doesn’t have volcanic activity or flowing water, but it does have wind that can wear down rocks and add dust to the atmosphere. The team led by Kevin Lewis and Lujendra Ojha studied the composition of the fine particles blowing around Mars, tracking them back to the Medusae Fossae formation. If that sounds familiar, it’s because Medusae Fossae has been the subject of extensive research over the years.

Medusae Fossae was discovered by NASA orbital Mars missions back in the 1960s. This wavy rock formation measures about 1.24 million square miles (2 million square kilometers), and scientists believe it was substantially larger before erosion took its toll. The long ridges that mark Medusae Fossae are signs of the erosion that shrunk the rocks and loaded the atmosphere up with fine, powdery dust.

The long ridges and valleys are produced by wind erosion, leading to a build-up of dust across the planet.

In a separate study earlier this year, this same team discovered that Medusae Fossae has volcanic origins. It formed from ash released about three billion years ago that eventually compressed into porous rock. Medusae Fossae has eroded quickly (on a geological scale) because it has a lower density than the rest of the rocks around it. The team estimated in the previous study that Medusae Fossae used to be twice as large as it is now.

Using data from missions spread across the planet, the team searched for a matching chemical signature. Martian dust has a surprisingly consistent makeup, so the team focused on Medusae Fossae early on. This formation has the same ratios of sulfur and chlorine found in the dust covering Mars. There’s no other viable source for all that dust.

Mars is covered in between two and 12 meters of dust. Without Medusae Fossae, it would be a completely different world.