Characteristics of Near-Polar Atmosphere/Thermosphere of Mars at Altitudes of 125–145 km: The Data of a Radio Occultation Experiment onboard the Mars Global Surveyor Spacecraft

Abstract

Using data from a radio occultation experiment onboard the Mars Global Surveyor spacecraft, altitude variations of the scale height of the neutral atmosphere in the northern and southern hemispheres of Mars are analyzed. The averaged altitude gradient of temperature for neutrals in the thermosphere is estimated. The revealed variations of the scale height of the neutral atmosphere at zenith angles of less than 82 ° indicate that the near polar atmosphere is not isothermal at altitudes of 125-145 km, which experimentally confirms predictions of models of the Martian atmosphere. It is shown that when one approaches the terminator the near polar atmosphere is cooled and the effects of variation of the solar zenith angle modulate the local time effects in both hemispheres.