Curiosity has been beaming back valuable scientific data since landing on Mars in August.
The search for signs of life on Mars may have suffered a setback.
NASA's Curiosity Rover has been analyzing air samples gathered from the Martian atmosphere.
NASA scientists announced Friday their initial analysis of the Martian atmosphere at the scan site did not detect any sign of methane -- a key byproduct of life.
"Methane is clearly not an abundant gas at the Gale Crater site, if it is there at all," said Chris Webster of NASA's Jet Propulsion Laboratory in Pasadena, California, in a release.
Traces of methane were remotely detected on the red planet by probes in 2003, sparking excitement in the scientific community.
While on Earth the gas can be released through geological processes, most of it is generated by biological organisms.
The rover used a special type of on-board instrument to scan the atmosphere sample.
The Martian air was pumped into small chamber and scanned with laser beams.
But Webster says even though no sign of methane was detected, the search continues.
"While we determine upper limits on low values, atmospheric variability in the Martian atmosphere could yet hold surprises for us," he said.
Part of Curiosity's mission is to search for signs that Mars may have once been able to support life.
It is also looking for clues about how the planet lost its atmosphere, which is now 100 times thinner than Earth's.