EYE IN THE SKY. For three Mars years, TES
tracked the weather on Mars, following the planet through its yearly
cycle. Mars dates are based on the Sun's longitude (Ls, seen at
bottom); northern hemisphere spring begins at Ls = 0. Click on the
image to download a larger version. NASA/JPL/Arizona State
Smith, M. D., Interannual variability in TES atmospheric observations of Mars during 1999-2003, Icarus, 167, 148-165, 2004.