Some of the most amazing scientific discoveries are actually happy accidents. Back in 2017, the otherwise sturdy Curiosity rover went through one of its first crises when its drill bit suddenly malfunctioned. Without this drill, much of Curiosity’s mission of finding signs of habitability, past or present, would have been seriously jeopardized. Luckily, NASA engineers repaired the system malfunction remotely, but a new study has reported what the rover found in that particular sample that Curiosity took exactly when the drill broke down.

Curiosity analyzes powdered samples drilled from rocks in order to measure the chemical fingerprints present in these various minerals and soils. This data helps scientists to determine the composition of Martian soil and rock, but also their history, especially as it relates to their past interaction with water. Gale Crater, where the rover was deployed, is believed to have once hosted a large body of water billions of years ago.

Typically, the sampling technique involves placing the dirt sample into an empty, dry cup. But when the drill bit broke down, the very last sample before the malfunction was placed into a cup containing a chemical cocktail made of reagents. The rover arrived on Mars equipped with nine of these pre-filled cups.

This type of sampling, known as a wet sampling experiment, caused a chemical reaction that allowed NASA researchers to identify organic molecules previously never observed on Mars.

“This experiment was definitely successful,” Maëva Millan, a postdoctoral fellow at NASA’s Goddard Spaceflight Center and lead author of the new study, tells Inverse. “While we haven’t found what we were looking for, biosignatures, we showed that this technique is really promising.”

In their new study published this week in the journal Nature Astronomy, NASA scientists have reported for the first time the presence of ammonia and benzoic acid on Mars. That was surprising since such molecules were thought to be nonviable due to the radiation presence on the Martian surface. Previously, other organic molecules identified by NASA included thiophenes, benzene, toluene, and some small molecules made of carbon chains.

Organic molecules are the building blocks of life. However, ammonia and benzoic acid aren’t exactly biosignatures — but the precursor molecules could be. That’s why scientists at NASA are now focused on finding these molecules that may indicate past habitability on the red planet. The 2022 ExoMars mission led by the European Space Agency (ESA) may provide this opportunity, as well as the Perseverance rover whose samples will be returned to Earth between 2028 and 2030. 

“Once we have found that, we can say where they originated from,” Millan says. “As of now, with all the molecules that we have found on Mars, we have made the hypothesis that they could come from geological processes.”