Martian Dune Mystery Solved by Bouncing Sand Grains

The way sand grains knock each other around turns out to make all the difference, Kok says. Because Martian gravity and air density are so much lower than Earth’s, a small kick from the wind sends sand particles on Mars flying much higher, up to a meter off the ground.

“It’s like playing golf on the moon,” Kok says. Particles get caught in stronger winds as they rise, causing them to pick up speed and ultimately slam into the ground, where they kick up more particles and start the cycle over. “This splashing process is really efficient,” Kok says. “It can keep saltation, or sand blowing, going on Mars at relatively low wind speeds.” These jumping sand grains can create ripples over time even without high sustained winds, he says.