First absolute wind measurements in the middle atmosphere of Mars

Abstract

The first absolute wind measurements in the middle atmosphere of Mars (40-70 km) were obtained from Doppler shifts in the J = 1-2 CO transition at 230.538 GHz. During the 1988 opposition, this line was observed at 100 kHz resolution with the IRAM 30 m telescope. The 12″ FWHM beam of the facility allowed spatial resolution of the Martian disk. The high S/N of the data allowed measurement of winds with a 1 σ absolute line-of-sight accuracy of 20 m/s. The measurements, performed during Southern summer solstice, stress the Southern hemisphere and clearly indicate a global easterlies flow