The Planetary Fourier Spectrometer (PFS) on board the ESA's Mars Express spacecraft malfunctioned a few months ago, and the agency wants to know why. The instrument was working perfectly for two years, and made the surprising discovery of methane in Mars' atmosphere. It might be malfunctioning because of spacecraft vibration, but the source of the problem is still under investigation. Even if engineers can't get the instrument working again, the spacecraft still has another 6 which are working fine.