Depths of the Relief Compensation and the Anomalous Structure of Crust and Mantle of Mars

TL;DR

This study analyzes Martian gravity and topography to determine the depths of compensation and the structure of the crust and mantle, revealing multiple compensation depths and possible mantle plume activity.

Contribution

It introduces a quadratic approximation method to determine topography compensation depths and maps their lateral distributions on Mars.

Findings

All topography compensation occurs within 0-1400 km depth range.

Multiple specific depths identified for topography compensation, including crust and mantle transition layers.

Evidence suggests mantle plumes may sustain Tharsis volcanic plateau anomalies.

Abstract

This study determined the contribution of Martian topography and the density jump at the Mohorovicic discontinuity (M) to the gravity in a quadratic approximation. It also resolved the problem of determining the possible depths of compensation for topography harmonics of various degrees and orders. It shows that all the topography compensation is within the depth range from 0 to 1400 km. Different topographic irregularities are most likely to be compensated at depths that correspond to the upper crust (d =(4.5 +- 3.7)km), crust-mantle transition layer (d = (78 +- 24)km), lithospheric boundary (d = (200 +- 34)km), upper-middle mantle transition layer (d = (400 +- 70)km), or middle-lower mantle transition layer (d =(1120 +- 180)km). This paper presents the lateral distributions of compensation masses for these depths and the respective maps. According to calculations, stresses in the Martian crust and mantle may be as high as 10^8 Pa. This paper shows that the topographic anomalies of the Tharsis volcanic plateau and the symmetric formation in the eastern hemisphere could have originated and be dynamically maintained by two plumes of melted mantle substance enriched with fluids; these plumes may have their origin at the boundary of the lower mantle.