This figure shows average temperature structure in the martian northern polar regions in six Mars Years as measured by Mars Climate Sounder on Mars Reconnaissance Orbiter and the Thermal Emission Spectrometer on Mars Global Surveyor. (Mars Year 1 started in 1956; Mars Year 25 started in June 2000; Mars Year 31 started in September 2011.) The profiles cover the atmosphere from the surface up to about 75 kilometers altitude. The profiles are from the aphelion season, when Mars is farthest from the Sun. This coincides with late northern spring (about three weeks before the start of summer). These night-time averages each cover 25 days of observations.

Courtesy David Kass, JPL