Deriving Mercury Geodetic Parameters With Altimetric Crossovers From the Mercury Laser Altimeter (MLA)

Abstract

Mercury is one of the most interesting objects in the Solar System, still challenging our understanding of planetary formation and evolution with its high density, unexpected magnetic field, and the 3:2 resonance between its rotational and orbital periods.

Mercury's Northern Rise Core‐Field Magnetic Anomaly

“…To test the dependence of our results on our parameter choices, we repeated our calculations for a range of ext L and inv L (Figure 4c) and obtained a mean source radius of 1,953 km with a standard deviation of 47 km over all ext L and inv L and optimal J. The consistency of our source depths confirmed the robustness of our result (Figure 4c) and places the source of the observed field at or below Mercury's core-mantle boundary (1,985 km  39 km Genova et al, 2019; 2,020 km  50 km Bertone et al, 2021, and see the discussion by Steinbrügge et al [2021]).…”

“…Solid line and gray area indicate the mean and one standard deviation for the magnetic anomaly source radius. Dashed lines denote means and hatched areas show standard deviations for the core-mantle boundary (Bertone et al, 2021;Genova et al, 2019).…”

“…We specified a non-zonal magnetic field model following the spectrum by Langlais et al (2014) for a chosen source depth. We used a source radius of 2,000 km, corresponding to a magnetic source close to Mercury's core-mantle boundary (Bertone et al, 2021;Genova et al, 2019). The model (Figure 2a) was evaluated at our data locations (Figure 2b) and Gaussian noise was added (Figure 2c) with a standard deviation 2.5-times that of the evaluated model to obtain synthetic data with characteristics similar to the filtered MESSENGER data (Figure 1g).…”

Evaluation of Recent Measurements of Mercury’s Moments of Inertia and Tides Using a Comprehensive Markov Chain Monte Carlo Method

“…Konopliv et al (2020) also provided an estimate of k 2 = 0.53 ± 0.03, consistent with the higher value of Genova et al (2019). Recent analysis of MLA altimetric crossovers (Bertone et al 2021) yielded an additional measurement of Mercury's obliquity that is fully consistent with the Cassini state, but this value is higher than that of Genova et al (2019), resulting in a higher polar moment of inertia of C/(MR 2 ) = 0.343 ± 0.006, and in a value of C m /C = 0.423 ± 0.012 (using the degree 2 coefficients from Genova et al 2019). Multiple combinations of the R.A. and decl.…”

“…Multiple combinations of the R.A. and decl. of the pole can satisfy the Cassini state requirement, as can be seen in, for example, Bertone et al (2021;Figure A1), resulting in different obliquities, and hence the discrepancy where two different obliquities satisfy the Cassini state.…”