A crustal magnetic field model of Mars with spherical harmonic degree up to 140

We develop a new crustal magnetic field model of Mars with spherical harmonic degree up to 140, which is based on orbiting measurements from Mars Global Surveyor (MGS), Mars Atmosphere and Volatile Evolution (MAVEN), and surface measurements from InSight and Zhurong. We follow the techniques from M14 model[Morschhauser et al., 2014] to inverse the spherical harmonic coefficients, including assigning different weights to the data of different sources, eliminating outliers with huber norm fitting, and employing the horizontal gradient of B_z component as L1 regularization term in the final model. It is found that our new model achieves the best spatial resolution ever before (~150 km). The unweighted misfits between our model and the MGS MPO, MGS AB/SPO and MAVEN are 8.0 nT, 9.9 nT, and 8.1 nT, respectively. Compared with the previous models, our model predictions are consistent with the surface measurements at InSight and Zhurong landing sites since the surface data are involved in the model inversion, which indicates the surface measurements are crucial to constrain the model downward continuation. The model characterizes the small-scale stratigraphic units on Mars, for example, the Lucus Planum, Apollinaris Patera, Hadriaca Patera, etc., contributing to the research of the structures of magnetic anomalies on Mars with different scales and the evolution of Martian dynamo.