Evaluating the Use of Seasonal Surface Displacements and Time-Variable
Gravity to Constrain the Interior of Mars
Abstract
The mass transport of volatiles on Mars represents a seasonally changing
load onto the lithosphere of the planet. Much like on Earth, as mass is
redistributed across the planet, the surface responds in a complex
manner becoming displaced downwards or upwards. The magnitude and extent
of displacement depend on the properties of the load and mechanical
properties of the planetary interior. Based on new estimates of the
height variation of the seasonal polar cap (SPC) we predict local
surface displacements of up to tens of millimeters with a strong degree
1 signal throughout the Martian year. The long-wavelength portion of the
displacement is potentially observable, with a magnitude of a few
millimeters, located away from the seasonal polar cap where we could
realistically measure it with a landed or orbital mission. We also model
the direct contribution of this process to observable time variable
gravity where we find the odd zonal coefficients to be in line with
previous measurements, although with a smaller magnitude. Future
measurements of this displacement could be used to help elucidate the
composition of the mantle and crust of Mars, using this process as a
probe into the Martian interior. Furthermore, more refined measurements
of time-variable gravity would be a powerful tool in constraining the
pole-to-pole volatile cycle present on Mars.