SCI2016_0001: SOFIA/GREAT [O I] spectrum at 4.7 THz (63 μm) superimposed on a picture of Mars. Absorption line depth is approximately 10% of the continuum. The abundance of atomic oxygen computed from the data is less than expected from the Forget et al. 1999 global circulation & photochemical model. Credit: SOFIA/GREAT spectrum: NASA/DLR/USRA/DSI/MPIfR/GREAT Consortium/MPIfS/Rezac et al. 2015; Mars image: NASA