Pre-mission InSights on the Interior of Mars

Abstract

The Interior exploration using Seismic Investigations, Geodesy, and Heat Transport (InSight) Mission will focus on Mars' interior structure and evolution. The basic structure of crust, mantle, and core form soon after accretion. Understanding the early differentiation process on Mars and how it relates to bulk composition is key to improving our understanding of this process on rocky bodies in our solar system, as well as in other solar B S.E. Smrekar

Hydrostatic Interfaces in Bodies With Nonhydrostatic Lithospheres

“…Though all harmonic degrees and orders will be considered, the largest contributor is for the C 20 term. The predicted contribution to the observed value for this harmonic is provided in Table for several density profiles that were employed in Smrekar et al (). As is seen, depending on the assumed density profile, between 4.4% and 6.4% of the observed C 20 gravity coefficient is a result of hydrostatic interfaces beneath the lithosphere.…”

“…For our first test, we make use of a density profile of Mars that is derived from the Mars bulk-silicate compositional model of Taylor (2013). This model (TAAK, see Table 4) has a core radius of 1,791 km and is taken from the Mars reference models presented in Smrekar et al (2019). The predicted hydrostatic flattening corresponds to a difference of 17 km between the poles and equator, and the observed values of h 20 and h 40 , our predicted values, and those predicted by the first-and second-order hydrostatic theories from the numerical code of Chambat et al (2010) are given in Table 1. Somewhat remarkably, our first-order results and the second-order results using the code of Chambat et al (2010) for the zonal degree-2 surface shape h 20 are found to differ by only 0.09%.…”

“…Lacking seismic constraints, the average thickness of the crust was adjusted iteratively in order to obtain a minimum crustal thickness of 1 km, which was always found to occur in the center of the Isidis impact basin. A thicker minimum crustal-thickness constraint could have been employed, and though not considered here, lateral variations in crustal density could also have been accounted for (see Plesa et al, 2016;Smrekar et al, 2019;Wieczorek et al, 2013). Our final crustal thickness model is displayed in the top panel of Figure 3.…”

“…Then using these results, we compute a new global crustal thickness map of the planet that accounts for the gravitational attraction of hydrostatic interfaces beneath the lithosphere. These global crustal thickness models will benefit from data that are being collected by the InSight seismometer (Lognonné et al, ; Smrekar et al, ). Following this, we then quantify how the lithospheric mass anomalies affect the free core nutation period of Mars that will be measured by the InSight spacecraft (Folkner et al, ).…”

Calibration of the Heat Flow and Physical Properties Package (HP) for the InSight Mars Mission

“…This indicates a lunar bulk concentration of heat producing elements similar to that of the Earth. Present-day Martian heat flow is estimated to be 14-25 mW m −2 (Plesa et al, 2015(Plesa et al, , 2018Parro et al, 2017;Smrekar et al, 2019), in between the lunar and terrestrial values. Present-day Martian heat flow is estimated to be 14-25 mW m −2 (Plesa et al, 2015(Plesa et al, , 2018Parro et al, 2017;Smrekar et al, 2019), in between the lunar and terrestrial values.…”