HR: 17:00h
AN: G42C-05 INVITED     [PDF]
TI: Estimation of Seasonally-varying CO$_2$ Ice Mass and Mean Atmospheric Pressure on Mars from Temporal Changes in the Gravitational Field
AU: * Zuber, M T
EM: zuber@mit.edu
AF: Department of Earth, Atmospheric and Planetary Sciences, 54-518 Massachusetts Institute of Technology, Cambridge, MA 02139-4307 United States
AB: The seasonal exchange of CO$_2$ between the atmosphere and cryosphere of Mars modifies the planetary mass distribution and results in small changes in the long-wavelength gravitational field. Over the course of the Martian year $\sim$18% of the total volatile mass will be exchanged between the atmosphere and the surface, resulting in a re-distribution of $\sim 1 \times 10^{-8}$ of the total mass of Mars. Changes in the Martian long-wavelength gravity field have been detected from orbiting spacecraft and the challenge is to relate these variations to the CO$_2$ cycle. In the current study we develop an analytical approach to relate gravity field changes to seasonal variations in CO$_2$ ice mass and to the global mean atmospheric surface pressure. We have also performed a direct recovery of temporally-varying cryospheric mass and demonstrate an equivalence to the recovery using low-degree gravity coefficients. In addition, we have estimated gravity anomalies over the poles, as yet another representation of the same phenomenon. We compare our estimates with Viking lander pressure measurements and with predictions from a General Circulation Model (GCM) simulation for a typical Mars year. This combined theoretical and observational approach provides a means of estimating the global-scale volatile mass exchange and global mean pressure on Mars on a routine basis from precise tracking of orbital spacecraft.
DE: 1227 Planetary geodesy and gravity (5420, 5714, 6019)
DE: 5417 Gravitational fields (1227)
DE: 6225 Mars
SC: Geodesy [G]
MN: 2003 Fall Meeting