Researchers from the University of Washington have discovered hundreds imprints of ancient sand piles — known as ghost dunes — on Mars’ surface, according to a recent study in the Journal of Geophysical Research.
The team found the remains in two different locations on the Red Planet, a discovery that could give insight into the world’s past climate.
The dunes formed back when the planet had both flowing water and active volcanoes. Such natural processes covered the formations with sediment about two billion years ago and slowly hardened them over time. Then, harsh winds blew the sand away from the inside and left the imprints behind.
This is not the first time astronomers have discovered ghost dunes on Mars — there are some in the Medusa Fossae formation for instance — but the new research identified 300 previously undiscovered ones in both the Hellas Basin and the Noctis Labyrinthus.
They made the discovery by looking at images of the Mars’ surface and then scanning the pictures for clusters of crescent-shaped pits. That unique shape indicates the dunes were “barchan dunes,” which form on flat surfaces with unidirectional winds.
Studying the orientation allowed scientists to determine that the winds came from the north and steadily pushed the dunes south. That is strictly different than the wind direction today, suggesting that environmental conditions on the planet shifted over time.
“One of the cool things about the ghost dunes is that they tell us, for sure, that the wind on Mars was different in the ancient past, when they formed,” said lead author Mackenzie Day, a researcher at the University of Washington, in a statement.
In addition, the team managed to figure out how big the dunes were. The ones in the Hellas Basin averaged 250 feet tall, while the ones in the Noctis Labyrinthus were roughly half that size.
The finding is interesting, and the researchers hope to follow up on their study could give new insight into the rocky landscape. There is also a chance that the wind did not fully clear the molds and that some ancient sand could still be stuck in them.
“There is probably nothing living there now,” added Day, according to Atlas Obscura. “But if there ever was anything on Mars, this is a better place on average to look.”