INTERPRETATION OF THE GLOBAL CLIMATIC CYCLES OF MARS BY USING THE AVAILABLE INFORMATION FROM ITS GEOLOGIC RECORD

Analysis and interpretation of the collected data from the NASA’s different missions to Mars indicate the occurrence of at least four major climatic cycles. These cycles are as follows: 1) extreme climatic cycle that existed during the early stage of Martian formation. Meteorite impacts, volcanic activities (outgassing), and crustal deformation (folds, faults, and joints), ridges, troughs, and dispersed craters were very common; 2 ) warm and wet cycle that associated with heavy rains, runoffs, and infiltration. The high precipitations developed stream channels, sinuous rills, gullies, fluvial fans, and drainage patterns. Consequently, the drainage channels jointed to flood most of the low-elevated continental interior and contributed in the formation of an epeiric sea (epicontinental sea). Sedimentary structures and microstructures including crossbedding, ripple marks, laminations of the hydrated silicate minerals, and formation of canyons strongly support the presence of liquid waters on Mars through that time. During this climatic cycle, life may existed in the Martian epicontinental sea in form of prokaryotic organisms (cynobacteria); 3) warm and dry cycle that is characterized by the presence of mud cracks, desert pavements, wind-transported sand, sand dunes, playa lakes, and abundance amount of evaporitic minerals including halite and gypsum; and 4) glacial and interglacial periods in which freezing and thawing conditions have contributed in the formation of glacial lakes, glacial varves, grooves, striations, tills, and tillites.

In this study, a general model is proposed to illustrate the paleoclimatic changes of Mars and the related depositional environments throughout the Martian geologic history.