The organic carbon was found in mud samples dating back 3.5 billion years, just after Mars lost its atmosphere.
The formations, shared by the alien-hunting SETI Institute, were probably formed by natural erosion.
The clouds of frozen carbon dioxide were photographed at an altitude of around 50 miles by NASA's Curiosity rover.
Curiosity has been exploring the red planet and gathering scientific data for almost a decade, having touched down on the surface on August 5, 2012.
Following years of analysis, the results of experiments conducted by the rover's SAM instrument, which searched for the building blocks of life on Mars, are in.
The car-sized vehicle has been operating on Mars since 2012.
Photos show black and white landscape view of Gale Crater taken as the rover investigates geological formations.
The rover is currently climbing the slopes of an 18-foot-high mountain on Mars.
The drill malfunctioned in December 2016.
The rover used its arm and camera ensemble to take a selfie on the Red Planet's Vera Rubin Ridge.
Fortunately, the scientists behind the rover love a good mystery.
New findings bolster the idea that life once existed on the red planet.