A NEW TECHNIQUE TO MEASURE TEMPERATURE PROFILES IN THE MARS' MIDDLE ATMOSPHERE

摘要

Measuring temperature in CO_2-rich atmospheres like those of Mars and Venus is challenging. As CO_2 absorbs most of the incoming radiation in the IR spectral region, spectra recorded by conventional instruments that use remote sensing in the thermal infrared (IR) region become saturated over a short distance. This renders measurements of temperature in the middle atmospheric region difficult. In fact, the temperature profile in the middle atmosphere of Mars about 40 to 120 km above the surface is poorly characterized [7]. One alternative is to use airglow measurements to derive temperature profiles. It is a cost-effective technique, since relatively simple photometers are used to measure the selected emission rates. This technique has not yet been exploited on Mars or Venus. We present here the first estimates of the Martian airglow emissions from the O_2 Herzberg I & II and Chamberlain bands using a time-dependent photochemical model. Preliminary results are presented, current limitations in terms of laboratory measurements are highlighted, and the feasibility of using those emissions to sound the temperature of the Martian neutral atmosphere in the aerobreaking altitude region is discussed. Our calculations show that the O_2 Herzberg II band system is the strongest emission and it reaches an intensity of 323.4 R assuming a direct excitation mechanism. It is therefore a possible candidate to derive the temperature profile in the middle atmosphere of Mars.