Ghost dunes that have been spotted on Mars may be the best chance of finding signs of alien life on the Red Planet, if it ever existed.

NASA recently revealed that the Curiosity rover found ancient organic matter on Mars. According to the study that detailed the discovery of the ghost dunes, the formations may be a better place than average to continue the search for microbes on the Red Planet.

Ghost Dunes On Mars: What Are They?

In a study that was published on the Journal of Geophysical Research, planetary geomorphologist Mackenzie Day and astrobiologist David Catling revealed that they discovered around 800 so-called ghost dunes in two different locations on Mars.

The ghost dunes are the negative spaces that were left behind by ancient sand dunes. Sediments in lava or water partially buried the dunes and then hardened, which preserved the contours. Wind then blew sand off the dunes' exposed tops and scoured them from inside, leaving solid molds in the shapes of the ancient dunes.

Day and Catling spotted around 300 ghost dunes on the Hellas Basin, which is a 1,600-mile-long impact crater that also features canyon systems and volcanic flows, and almost 500 ghost dunes on the Noctis Labyrinthus, which is a system of steep valleys that look like a maze.

By looking at the orientation of the ghost dunes, the researchers determined the direction that the wind was blowing. In both clusters, the winds came from the north and slowly pushed the dunes south, different than the winds in the areas today and indicating that the environmental conditions on Mars have since changed.

Understanding the wind in Mars' past may help researchers reconstruct the travel of sediments on the planet's surface, how the Red Planet's major features were formed, and how different the ancient climate was compared to the Martian climate today.

How Will Ghost Dunes Prove Life On Mars?

According to the researchers, the ghost dunes may hold important clues on signs of ancient life on Mars.

Day and Catling pointed out that there is the possibility that the wind did not completely clear out the molds. In such cases, some ancient sand, including whatever was in them, could still be stuck inside the ghost dunes, which may have protected them from destructive elements such as surface radiation.

"There is probably nothing living there now," said Day. "But if there ever was anything on Mars, this is a better place on average to look."