Mars thermosphere extends from 90 KM to the exobase (CA. 200 KM). Thermosphere variability at mars is driven primarily by forcing from its lower atmosphere, and by the absorption of variable solar EUV…

The University of Colorado, Boulder was awarded a $533,094 grant by the National Aeronautics and Space Administration (NASA) to conduct research on the dynamics of the Martian thermosphere, the upper atmosphere layer extending from 90 km to the exobase at around 200 km. The project will focus on understanding the coupling between the lower/middle Martian atmosphere, as measured by the Mars Climate Database, and the thermosphere up to the exosphere, including the aerobraking region between 100-120 km altitude. The research aims to provide new insights into the origins and predictability of aerobraking-region atmospheric densities, which impact spacecraft operations. The grant is not associated with a larger contracting vehicle and does not have a set-aside designation.

Mars thermosphere extends from 90 KM to the exobase (CA. 200 KM). Thermosphere variability at mars is driven primarily by forcing from its lower atmosphere, and by the absorption of variable solar EUV radiation. Modeling and scattered observations indicate that mars thermosphere is furthermore distinguished by its longitudinal variability, which varies with latitude, season (LS), and height. We also know that since traveling planetary waves (PW) do not extend appreciably above 100 KM, that most longitudinal variability is attributable to the spectrum of solar tides propagating up from below, with some additional contributions from stationary PW (SPW) excited in-situ by tide-tide nonlinear interactions. In a 2020 paper by the PI, IT is shown that the mars climate data base (MCD), which is based on a first principles model extending from mars surface to the exosphere, approximates well the tidal spectrum at 75 KM altitude measured by MRO/MCS, and provides new insights into the origins of longitudinal density structures at aerobraking altitudes (100-120 KM). The project focuses on understanding the dynamical coupling between the lower/middle atmosphere of mars as embodied in 75-KM altitude MCS measurements, and the thermosphere up to the exosphere (CA. 90-200 KM) and including the aerobraking region (100-120 KM). New insights into the origins and potential predictability of aerobraking-region densities is expected to emerge. Since tidal dissipation is a major contributor to the zonal-mean circulation and specifically the hadley-type cell that extends into the thermosphere, new insights into the LMD GCM s capability to model transport of H2O and H2 into the thermosphere and exosphere are also expected to emerge.