Curiosity comes up empty-handed in its first attempt to find the gas, which on Earth is tied to biological processes.
After more than a month of searching, scientists using NASA's rover Curiosity to study Mars' atmosphere have found no evidence that the planet most like Earth in the solar system has methane, a gas tied to biological processes.
The finding adds a new twist into a puzzling story about methane on Mars, which previously was detected by ground-based telescopes and orbiting spacecraft.
"Maybe its understandable because it's a very early measurement and they're just really still learning the idiosyncrasies of the instrumentation," planetary scientist Michael Mumma, with NASA's Goddard Space Flight Center in Greenbelt, Md., told Discovery News.
Mumma led a team that found methane in Mars' atmosphere in 2003.
On Earth, living systems produce more than 90 percent of the methane in the atmosphere, with the rest tied to geochemical processes. The gas is easily broken down by sunlight, so its presence in the Martian atmosphere would imply a continuous source on the planet's surface.