Admissible height of local roughness of Titan's landscape

Titan's landscape has been formed by both short-term phenomena, such as int ernal tectonic processes and atmospheric activity, and long-term factors of planetary scale, such as global stress and gravity forces. Short-term phen omena can be ignored since the timescale of any relaxation process 5x10(14) s is shorter than Titan's lifetime 1.4x10(17) s. Global stress can be igno red as well, because Titan's figure is practically a right sphere. Thus bot h Titan's body as a whole and the crust in particular are free from any str ess, except the gravity force. For the cold, stable, incompressible Titan, the only significant relief-forming factor is the counteraction between the gravity force and the crust's ability to resist this force. This results i n a simple estimation of the maximal height of any admissible feature locat ed above ocean level (RAOL) H-max = 3 sigma/rho g. The issue is the proper estimation of the crust density and real shear stress. Chemically, Titan's crust is an ice-rock medium, while physically, it is a frozen two-phase sys tem, the density of the crust being equal to 1.81x10(3) kg m(-3). Titan's c rust is considered here to be similar to Earth's permafrost, corrected for a lower temperature. This medium was treated as a quasi-isotropic entity th at is subjected to a slow viscoelastic deformation, the ultimate shear stre ss being equal to 2.15 MPa. The estimation of the admissible height of Tita n's RAOL results eventually in H-max similar to 1900 m. The validity of the gravitational approach was verified by the calculation of known H-max for the rocky inner planets, Earth, Venus, Mars, and the icy Jovian satellites, Ganymede and Callisto, and it appears to be reliable within similar to 50% .