This image shows the temperature of the martian surface measured by the Mars Global Surveyor Thermal Emission Spectrometer (TES) instrument. On September 15, 3 hours and 48 minutes after the spacecrafts third close approach to the planet, the TES instrument was commanded to point at Mars and measure the temperature of the surface during a four minute scan. At this time MGS was approximately 15,000 miles (~24,000 km) from the planet, with a view looking up from beneath the planet at the south polar region. The circular blue region (- 198 F) is the south polar cap of Mars that is composed of CO₂ ice. The night side of the planet, shown with crosses, is generally cool (green). The sunlit side of the planet reaches temperatures near 15 F (yellow). Each square represents an individual observation acquired in 2 seconds with a ground resolution of ~125 miles (~200 km). The TES instrument will remain on and collect similar images every 100 minutes to monitor the temperature of the surface and atmosphere throughout the aerobraking phase of the MGS mission.