NASA’s Curiosity rover may have brought scientists closer to finding signs of past life on Mars after detecting organic compounds in a rock sample nearly a year ago.

While such compounds can form through non-biological processes, researchers concluded that these alone could not account for the findings, leaving open the possibility that life once existed on the planet.

The study, published Feb. 4 in Astrobiology, stops short of confirming past life but highlights the significance of the discovery.

Curiosity, along with the Perseverance rover, has been exploring Mars to search for evidence of ancient habitability, USA Today has reported.

Since landing in Gale Crater in August 2012, Curiosity has collected 42 powdered rock samples to study the planet’s geology and potential biosignatures.