High‐resolution local magnetic field models for the Martian South Pole from Mars Global Surveyor data

Abstract

We present two high-resolution local models for the crustal magnetic field of the Martian south polar region. Models SP130 and SP130M were derived from three-component measurements made by Mars Global Surveyor at nighttime and at low altitude (<200 km). The availability area for these data covers the annulus between latitudes −76 ∘ and −87 ∘ and contains a strongly magnetized region (southern parts of Terra Sirenum) adjacent to weakly magnetized terrains (such as Prometheus Planum). Our localized field inversions take into account the region of data availability, a finite spectral bandlimit (spherical harmonic degree L = 130), and the varying satellite altitude at each observation point. We downward continue the local field solutions to a sphere of Martian polar radius 3376 km. While weakly magnetized areas in model SP130 contain inversion artifacts caused by strongly magnetized crust nearby, these artifacts are largely avoided in model SP130M, a mosaic of inversion results obtained by independently solving for the fields over individual subregions. Robust features of both models are magnetic stripes of alternating polarity in southern Terra Sirenum that end abruptly at the rim of Prometheus Planum, an impact crater with a weak or undetectable magnetic field. From a prominent and isolated dipole-like magnetic feature close to Australe Montes, we estimate a paleopole with a best fit location at longitude 207 ∘ and latitude 48 ∘ . From the abruptly ending magnetic field stripes, we estimate average magnetization values of up to 15 A/m.

Paleopole Reconstruction of Martian Magnetic Field Anomalies

“…Models of the magnetic field of Mars usually represent the field in terms of Equivalent Source Dipoles (ESD) (e.g., Langlais et al, ; Purucker et al, ) or spherical harmonic (SH) functions (e.g., Arkani‐Hamed, , ; Morschhauser et al, ). The most recent global SH model is expanded up to degree and order 110 (Morschhauser et al, ), and local models have been expanded to degree and order 130 (Plattner & Simons, ). Using MGS data (Frawley & Taylor, ; Hood & Zakharian, ; Hood et al, , ; Langlais & Purucker, ; Milbury et al, ; Quesnel et al, ; Richmond & Hood, ) or field models derived from these data (Arkani‐Hamed, ; Arkani‐Hamed & Boutin, ; Plattner & Simons, ), a number of studies have tried to constrain the characteristics of the Martian core dynamo field during the Noachian period.…”

“…The most recent global SH model is expanded up to degree and order 110 (Morschhauser et al, ), and local models have been expanded to degree and order 130 (Plattner & Simons, ). Using MGS data (Frawley & Taylor, ; Hood & Zakharian, ; Hood et al, , ; Langlais & Purucker, ; Milbury et al, ; Quesnel et al, ; Richmond & Hood, ) or field models derived from these data (Arkani‐Hamed, ; Arkani‐Hamed & Boutin, ; Plattner & Simons, ), a number of studies have tried to constrain the characteristics of the Martian core dynamo field during the Noachian period. Assuming that the main field was of dipolar character (Lillis et al, ), paleopole locations have been derived for a number of crustal magnetic field anomalies.…”

Terrestrial Water Storage in African Hydrological Regimes Derived from GRACE Mission Data: Intercomparison of Spherical Harmonics, Mass Concentration, and Scalar Slepian Methods

“…As a result, the leakage errors are attenuated from the surrounding areas, and spatial resolutions inside the ROI are increased [35]. The method has been applied to different geophysical and planetary phenomena, such as: (1) mapping the spatiotemporal loss of the ice shields [35]; (2) earthquake-derived gravity changes [37,38]; (3) deriving the TWS in the Amazon basin [39] and high plain aquifer [28]; (4) estimating the ocean bottom pressure signal [39]; and (5) obtaining a high local resolution model for the Mars south pole’s magnetic field [40]. Among the different CBF methods, the scalar Slepian localization approach can deduce a reliable TWS estimate for small and irregularly shaped ROI [28].…”

Utility of Slepian basis functions for modeling near-surface and satellite magnetic anomalies of the Australian lithosphere

“…Slepian functions (Slepian 1983) have been used for modeling noisy regional potential fields over an incomplete portion of the globe (Simons and Dahlen 2006), and to study gravity (e.g., Han and Simons 2008;Han 2008;Wang et al 2012) and magnetic (e.g., Beggan et al 2013;Plattner and Simons 2015) fields. However, the joint inversion of near-surface and satellite altitude magnetic observations relies on relatively standard least squares weighting procedures (e.g., Ravat et al 2002;Menke 2012).…”

“…The Slepian method also has been used to evaluate the continental and oceanic power spectrum components from the global spherical harmonic coefficients of the geomagnetic field (Beggan et al 2013), and for modeling south polar Martian magnetic anomalies from the Mars Global Surveyor satellite data (Plattner and Simons 2015). These Slepian-based studies, however, were restricted to single-altitude grids of satellite-based observations.…”