In 2004, scientists working with the European Space Agency's Mars Express orbiter reported traces of methane. (sciencemag.org)
But in late March, researchers analyzing data from the European Mars Express satellite reported the planet's atmosphere contains traces of methane, a by - product of bacteria here on Earth. (discovermagazine.com)
From October 2012 to June 2013, Curiosity used its Tunable Laser Spectrometer (TLS) six times to search for traces of methane in the Martian atmosphere. (extremetech.com)