NASA’s Curiosity rover has discovered the largest organic compounds ever found on Mars, sparking speculation about the possibility of past life on the planet.

The compounds, long-chain alkanes, were found in a 3.7 billion-year-old rock from an ancient Martian lakebed.

While these molecules can form through both chemical and biological processes, they are key components of cell membranes on Earth, raising the possibility they could be remnants of ancient Martian life.

Though not conclusive evidence of life, the discovery offers the best chance yet of finding biological remnants on Mars, The Guardian has reported.

Further analysis of additional samples may help clarify the origins of these compounds, but definitive answers will require future sample-return missions to Earth.

Written by B.C. Begley