Curiosity images mysterious 'pits' on Martian soil: What does NASA have to say about them?

“After Curiosity’s 14 years on the surface, Mars continues to surprise,” wrote Michelle Minitti in a NASA blog post published on September 3. Minitti, who’s the Deputy Principal Investigator of the Mars Hand Lens Imager (MAHLI) onboard NASA’s Curiosity rover, was referring to a group of ‘pits’ on the Martian soil that the instrument had imaged last month, between mission days 4988 and 4994.

But what is so special about these pits?

Minitti explained that pits on the Red Planet are quite common—tough pebbles often weather out their host rocks, leaving behind a void. “But the pits of this week were much broader and shallower than past features and were not accompanied by obvious objects that were once in the pits,” she explained. 

While NASA is not sure as to how these pits came to be, Minitti said that they are a “welcome new puzzle” in the study of the processes that have shaped the rocks on the slopes of Mount Sharp, which Curiosity has been climbing since 2014. Both MAHLI and Mastcam took images that will be used to map the structures in three dimensions and will help researchers understand them better.

The pits were far from the only features in the region that caught the attention of the Curiosity team. In fact, the bedrock itself was quite interesting, with layers that changed their appearance over short distances. “These might be evidence of changes in depositional conditions captured in close proximity to one another,” Minitti speculated. 

Curiosity was directed to analyze stubborn grey layers that stood out from the bedrock, hinting at a different chemical makeup. It also looked into a gray float rock (like the small pebbles seen in the first slide) and tried to figure out its origins, but it will be a while before the analysis yields results.