Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climate change on Mars

A key question regarding the evolution of Mars is related to the behavior of its volatiles. The present investigation is concerned with the global and seasonal abundances of water vapor in the Mars atmosphere as mapped by the Viking Mars Atmospheric Water Detector (MAWD) instrument for almost 1-1/2 Martian years from June 1976 to April 1979. Attention is given to the implications of the observed variations for determining the relative importance of those processes which may be controlling the vapor cycle on a seasonal basis. The processes considered include buffering of the atmosphere water by a surface or subsurface reservior of ground ice, physically adsorbed water, or chemically bound water. Other processes are related to the supply of water from the residual or seasonal north polar ice cap, the redistribution of the vapor resulting from atmospheric circulation, and control of the vapor holding capacity of the atmosphere by the local atmospheric temperatures.

The seasonal and global behavior of water vapor in the Mars atmosphere: Complete global results of the Viking Atmospheric Water Detector Experiment

The astronomical theory of climatic change on Mars

Numerical simulations of the Martian atmosphere general circulation are carried out for 50 simulated days, using a three-dimensional model, based on the primitive equations of meteorology, which incorporated the radiative effects of atmospheric dust on solar and thermal radiation. A large number of numerical experiments were conducted for alternative choices of seasonal date and dust optical depth. It was found that, as the dust content of the winter polar region increased, the rate of atmospheric CO2 condensation increased sharply. It is shown that the strong seasonal variation in the atmospheric dust content observed might cause a number of hemispheric asymmetries. These asymmetries include the greater prevalence of polar hoods in the northern polar region during winter, the lower albedo of the northern polar cap during spring, and the total dissipation of the northern CO2 ice cap during the warmer seasons.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/JB095iB02p01447%4010.1002/%28ISSN%292169-9356.POLMARS1

Simulations of the general circulation of the Martian atmosphere: 1. Polar processes

Wind friction threshold speeds for particle movement were determined in a wind tunnel operating at martian surface pressure with a 95 percent CO2 and 5 percent air atmosphere. The relationship between friction speed and free-stream velocity is extended to the critical case for Mars of momentum thickness Reynolds numbers between 425 and 2000. It is determined that the dynamic pressure required to initiate saltation is nearly constant for pressures between 1 bar and 4 mb for atmospheres of both air and CO2.

Threshold windspeeds for sand on Mars: Wind tunnel simulations

The imaging systems on board the two Viking landers have documented eolian processes and condensate formation on the Martian surface during the first Mars year of operation. During the winter, the formation of what appeared to be solid H2O and CO2 at the Viking 2 lander site was noted. The condensate formation suggested that solar radiative heating dominates atmospheric conductive heating on Mars. In addition, the Viking observations indicated that Martian surface erosion due to dust distribution may be lower than previously thought.

https://science.sciencemag.org/content/sci/204/4395/799.full.pdf

Susan L. Bragg

Papers

One Mars year: viking lander imaging observations.