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.