Nasa’s Curiosity rover has found organic matter preserved on Mars. The discovery suggests the red planet could have once been home to life.

“The chances of being able to find signs of ancient life with future missions, if life ever was present, just went up,” said Curiosity’s project scientist, Ashwin Vasavada of NASA’s Jet Propulsion Laboratory in Pasadena, California.

The organic molecules were found in Gale Crater — believed to once contain a shallow lake the size of Florida’s Lake Okeechobee. For the past six years, Curiosity has sifted samples of soil and ground-up rock for signs of organic molecules.

The new announcement is actually the result of two new studies. One is that the rover has found carbon-containing organic matter in 3.5-billion-year-old rock. The other result is that methane levels around Curiosity are being stored underneath the surface of the planet. Seasonal changes appear to bring that methane out and onto the surface. Combined, these results present tantalizing hints of a potentially habitable Martian past.

“With these new findings, Mars is telling us to stay the course and keep searching for evidence of life,” said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters, in Washington. “I’m confident that our ongoing and planned missions will unlock even more breathtaking discoveries on the Red Planet.”

The nuclear-battery-powered Curiosity rover, a $2.5 billion mobile chemistry lab,  launched in 2011. NASA calls the Curiosity the “largest and most capable” rover ever to make contact with Mars.