NASA’s Curiosity rover has been crawling across the dusty, windswept plains of Mars, drilling into rocks and, in the process, revealing the Red Planet’s geological history. Now, it has stumbled upon its most compelling chemical clues yet: large organic molecules resembling fatty acids.

The NASA rover "Curiosity" discovered what scientists say is the largest ever seen organic molecules on Mars, raising speculation about if life was created billions of years ago on the Red Planet.

NASA’s Curiosity rover has unearthed the largest organic molecules ever detected on Mars—possible fragments of fatty acids—hinting at the tantalizing possibility that prebiotic chemistry on the Red Planet may have been more advanced than previously thought.