Though the levels are far below those found on Earth, methane is a key indicator that life may be or may once have been present. In addition, the nuclear-powered explorer has also detected the first confirmed organic compounds in drill samples taken from Martian rocks.
NASA says that the methane was detected by the Sample Analysis at Mars (SAM) laboratory, which is one of the on-board experiments carried by Curiosity. Over a 20-month period, it took air samples and used its Tunable Laser Spectrometer to measure the amount of methane present. Until now, methane levels on the surface of Mars have been so small that early results indicated that it was non-existent, but low and variable levels have now been confirmed.
According to the NASA, the levels jumped to seven parts per billion in late 2013 and early 2014, which is ten times the amount detected at other times of the year. NASA scientists say that the sharp up and down increases in methane indicate a local source, which may be biological or chemical in nature and may be due to some release from a below-ground source.