Explore the rolling dunes of our solar system

This flight depends on the speed of the wind: wind tunnel experiments suggest that the movement of a grain of sand on Mars takes a gust 10 times stronger than necessary for the same grain on Earth. But once the sand starts moving, it’s easier to hold it, thanks to the planet’s weaker gravity. “The big unknown for Mars is the threshold you need to start sand movement,” says Simone Silvestro, a researcher at the National Institute of Astrophysics (INAF) in Italy.

For decades, scientists have suspected that the dunes they saw on Mars were ancient relics of a past characterized by a thicker atmosphere and stronger winds. That changed in 2019, when Silvestro and his colleagues used NASA’s Mars Reconnaissance Orbiter to capture crawling dunes near the Martian equator. By comparing images taken more than seven years apart at two different sites, the team determined that these megariples – which are the largest of the dunes at about 3 feet (1 meter) tall – edge at about 4 inches (10 centimeters) per year.

Even today, scientists are uncertain about the strength of surface winds on Mars. They mapped global wind patterns based on topography and landscape formation, but the bulk of the planet’s atmospheric measurements have been made by orbiters, which are limited to observing the upper atmosphere. Meanwhile, landers and rovers can only provide wind speed information at ground level; this leaves a large expanse of sky devoid of atmospheric measurements.

Ideally, a rover or lander would sit in one place and constantly watch the movement of the sand, rather than in timed snapshots, Diniega says. This would allow researchers to base their models on truth. Since the windy, dust-filled air has the potential to clog and damage robotic explorers, it would be even better, Silvestro says, to send people to the planet to measure wind speed and motion. dunes.

Arline J. Mercier