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The global gravity field of Mars reveals an active interior
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  • Barend Cornelis Root,
  • Weilun Qin,
  • Cedric Thieulot,
  • Youandi van der Tang
Barend Cornelis Root
Delft University of Technology

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Weilun Qin
Delft University of Technology
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Cedric Thieulot
Utrecht University
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Youandi van der Tang
Delft University of Technology
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Abstract

Mars hosts the largest volcano in our solar system, Mons Olympus. Up until now, flexural isostasy has commonly been used to understand the relationship between observed topography, crustal structure, and gravity. NASA’s InSight mission has brought new information about the Martian lithosphere, which warrants a re-analysis of the support of the large volcanic complex. After conducting spectral analysis on the topographic and gravity results from the flexural models, the gravitational signal of Martian topography with thin shell compensation fits well with the observed free-air anomaly for degrees, n≥2. The Martian lithosphere can be modelled by a thin shell model using the following parameters: crustal thickness of 60 ±10 km, crustal density of 3050 ±50 kg/m3, mantle density of 3550 ±100 kg/m3, and the best-fit elastic thickness (Te) is found to be 80 ±5 km. The remaining short scale gravity residuals give insight in Martian crustal density distributions. There appear to be buried mass anomalies in the subsurface of the northern polar plains, suggesting an older history of the northern hemisphere of Mars. A mismatch between modeled and observed gravity field for the long-wavelengths (between n=2-6 degrees) exists. The location of the residual anomaly correlates with the Tharsis Rise. which suggests active large-scale dynamic support of the volcanic region. A substantial negative mass anomaly in the mantle underneath the Tharsis Region can explain the gravity residual. Could mantle convection is still be active in Mars, explaining the relatively young geologic surface volcanism on Mars.