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Gravity Models of the Elysium Dome on Mars
| Content Provider | Semantic Scholar |
|---|---|
| Author | Janle, Peter Ropers, J. |
| Copyright Year | 1982 |
| Abstract | P. Janle, Institut fiir Geophysik, D-2300 Kiel, and J. Ropers, Rechenzentrum der Universitbt, D-200 Hamburg 13. Line-of-sight (L0S)-Doppler gravity is calculated for density models of the Elysium dome on Mars. The model gravity is fitted to the observed LOSgravity of Vik. Orb. I1 mission Rev. 511. The models comprise the topography which has been generalized by topographic discs (TD1 etc., Fig. 1) and lateral density variations with a normal density depth distribution of 3.0 g/cm3 for the crust and 3.5 g/cm3 for the upper mantle (1); 2.8 g/cm3 has been assumed for the topography (Figs. 1,2). Airy or a modified Pratt isc-, static compensation (2) have been considered for the construction of the density models. The gravity attraction of all topographic discs (Fig. 1) yields 222 mgal in comparison to 87 mgal of the observed gravity. Thus, the dome should be partially or totally compensated dependingon the value of the mean crustal thickness T. The following Airy models are consistent with the gravity data (Figs. 1,3): compensations of 89.1%, 97.5%, and 100% with T=50, 100, and 120 km. A 100% compensation is unlikely, because Elysium Mons and, to a less degree, Hecates Tholus are surrounded by extensional lineaments and therefore are probably uncompensated. An estimation of shear stresses in the upper mantle (3) from the Airy model of Fig. 1 (T=50) yields 148 bar in a depth of 140 km. As less compensated models imply smaller Ts and higher stresses, very thin Ts are unlikely for the relatively old Elysium dome. Thus, a T of about 30 km (86.1% compensation) should be the lower limit. Models considering modified Pratt isostasy (2) are consistent with T=50 and 80 km and a (minimum) thickness of the lower lithosphere L of 100 km. Thus, T (or the upper lithosphere) and L give a minimum lithospheric thickness of 150 km. Summary. Limits of the mean crustal thickness of 30 to 100 km can be determined for the Elysium area from Airy models. A minimum lithospheric thickness of 150 krn results from Pratt models. As the uncompensated Airy models yield shear stresses of more than 1 0 0 bar down to a depth of 250 km and as terrestrial upper mantle strengths may be less than 100 bar ( 4 ) , an increase of the minimum lithospheric thickness up to 250 km should be considered. References (1) Johnston, D.H. and Toksbz, M.N. (1979). Icarus 32, 73-84. -(2) Sleep, N.H. and Phillips, R.J. (1979). Geophys. Res. Letters 6, 803-806. (3) Janle, P. (1981). J. Geophys. 49, 57-65. (4) Phillips, R.J. and Lambeck, K. (1980). Rev. Geophys. Space Phys. 18, 27-76. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://www.lpi.usra.edu/meetings/lpsc1982/pdf/1188.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
