The Seasonal Behavior of Water Ice Clouds in the Tharsis and Valles Marineris Regions of Mars: Mars Orbiter Camera Observations

The Voyager and Galileo images of Europa and the Viking Orbiter images of Phobos revealed the surface cracking and fracture systems of the satellites of Jupiter and Mars. The complex system of lineaments and grooves cover the whole surface of these satellites. Based on earlier studies we compared the main characteristics of these structures and propose a joint model of the layered structure (Phobos) and the tidal fractured structure (Europa). However, more details are needed about the relevance of these models. Introduction Viking Orbiters transfered good images of Phobos in 1976. The system of linear striations, lineaments (grooves) were found to cover the surface which were distinguished morphologically and were classified into three types according to their characteristics: a) morphology, b) geometrical distribution on the surface, and c) relation with orbital motion of Phobos. According to the global character of the third system: that system was interpreted as expression of the probable inner layered structure of Phobos [1-6]. Fig. 1. The lineament system of Phobos on a Vikingimage. In studies of the Voyager and Galileo images the cracking system of Europa has been mapped [7] and on the basis of tidal stress field studies [8] the global pattern of the Europa cracking system was concluded as expression of the stress field on the surface of Europa generated by the tidal forces of the near giant Jupiter. Fig. 2. The cracking system of Europa Comparison of the two global patterns show strong similarities in the following characteristics. Both systems have a fractured "polar" region and a counterpart similarly fractured "antipolar" region. These fractured polar and antipolar regions are "connected" by various lineaments (Fig. 3., and Fig. 4.). But the comparison showed differences between the two systems, too. The third system of lineaments of Phobos [4] consists of lineaments forming arcs which are forming parallel planes which are perpendicular to the PhobosMars axis. Therefore the "polar" region of this system is 90 degrees rotated from the sub-planetary (subMartian) point (and its opposite point on the far side of Phobos) is in accord with this system (Fig. 3.). On Europa the fractured "polar" region is in the vicinity of the sub-planetary (sub-Jovian) point and its counter-polar region at the anti-sub-planetary point. Sixth International Conference on Mars (2003) 3198.pdf