THE STRUCTURE OF THE UPPER-ATMOSPHERE OF MARS - IN-SITU ACCELEROMETERMEASUREMENTS FROM MARS GLOBAL SURVEYOR

The Mars Global Surveyor (MGS) z-axis accelerometer has obtained over 200 vertical structures of thermospheric density, temperature, and pre ssure, ranging from 110 to 170 kilometers, compared to only three prev ious such vertical structures. In November 1997 a regional dust storm in the Southern Hemisphere triggered an unexpectedly large thermospher ic response at mid-northern latitudes, increasing the altitude of ther mospheric pressure surfaces there by as much as 8 kilometers and indic ating a strong global thermospheric response to a regional dust storm. Throughout the MGS mission, thermospheric density bulges have been de tected on opposite sides of the planet near 90 degrees E and 90 degree s W, in the vicinity of maximum terrain heights. This wave 2 pattern m ay be caused by topographically-forced planetary waves propagating up from the lower atmosphere.