Key Points:• SH model up to degree and order 110 of the magnetic lithospheric field of Mars • Several techniques have been used to obtain a stable and wellresolved model • Anomalies over small craters, volcanoes, and isolated anomalies are described Supporting Information:• Readme • Figure S1• Figure S2 • Figure S3 • Figure S4 • Figure S5 • Figure S6 • Figure S7 • Figure S8 • Figure S9 • Table S1 • Table S2 • Table S3 • Table S4 • Table S5 • Table S6 Correspondence to: A. Morschhauser, achim.morschhauser@dlr.de Citation:Morschhauser, A., V. Lesur, and M. Grott (2014) Abstract We present a model of the lithospheric magnetic field of Mars which is based on Mars GlobalSurveyor orbiting satellite data and represented by an expansion of spherical harmonic (SH) functions up to degree and order 110. Several techniques were applied in order to obtain a reliable and well-resolved model of the Martian lithospheric magnetic field: A modified Huber-Norm was used to properly treat data outliers, the mapping phase orbit data was weighted based on an a priori analysis of the data, and static external fields were treated by a joint inversion of external and internal fields. Further, temporal variabilities in the data which lead to unrealistically strong anomalies were considered as noise and handled by additionally minimizing a measure of the horizontal gradient of the vertically down internal field component at surface altitude. Here we use an iteratively reweighted least squares algorithm to approach an absolute measure (L1 norm), allowing for a better representation of strong localized magnetic anomalies as compared to the conventional least squares measure (L2 norm). The resulting model reproduces all known characteristics of the Martian lithospheric field and shows a rich level of detail. It is characterized by a low level of noise and robust when downward continued to the surface. We show how these properties can help to improve the knowledge of the Martian past and present magnetic field by investigating magnetic signatures associated with impacts and volcanoes. Additionally, we present some previously undescribed isolated anomalies, which can be used to determine paleopole positions and magnetization strengths. IntroductionThe Mars Global Surveyor (MGS) spacecraft operated from 1997 to 2006 in Martian orbit and was the first mission to provide magnetic field measurements of Mars at a sufficiently low altitude to reveal the characteristics of the Martian magnetic field. The early mission phases include the aerobraking and science phase orbits (AB/SPO), which are characterized by strongly varying altitudes. At altitudes below 200 km, these early mission phases provide mainly dayside data with sparse global coverage [Acuña et al., 1999]. They are complemented by the later mapping phase orbit (MPO) data, which provide dense global coverage during dayand nighttime at a nearly constant altitude of around 400 km.Earliest results based on AB/SPO data already indicated that Mars does not possess a relevant large-scale magnetic ...

In December 2019, the International Association of Geomagnetism and Aeronomy (IAGA) Division V Working Group (V-MOD) adopted the thirteenth generation of the International Geomagnetic Reference Field (IGRF). This IGRF updates the previous generation with a definitive main field model for epoch 2015.0, a main field model for epoch 2020.0, and a predictive linear secular variation for 2020.0 to 2025.0. This letter provides the equations defining the IGRF, the spherical harmonic coefficients for this thirteenth generation model, maps of magnetic declination, inclination and total field intensity for the epoch 2020.0, and maps of their predicted rate of change for the 2020.0 to 2025.0 time period.

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Please cite this article as: Morschhauser, A., Grott, M., Breuer, D., Crustal recycling, mantle dehydration, and the thermal evolution of Mars, Icarus (2010), doi: 10.1016/j.icarus.2010 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Crustal recycling, mantle dehydration, and the thermal evolution of Mars Mars would then be driven by the extraction of a primordial crust after core formation, cooling the mantle to temperatures close to the peridotite solidus. According to this scenario, the second stage of global crust formation took place over a more extended period of time, waning at around 3500 Myr b.p., and was driven by heat produced by the decay of radioactive elements. Present-day volcanism would then be driven by mantle plumes originating at the core-mantle boundary under regions of locally thickened, thermally insulating crust. Water extraction from the mantle was found to be 1 relatively efficient and close to 40 percent of the total inventory was lost from the mantle in most models. Assuming an initial mantle water content of 100 ppm and that 10% of the extracted water is supplied to the surface, this amount is equivalent to a 15 m thick global surface layer, suggesting that volcanic outgassing of H 2 O could have significantly influenced the early Martian climate and increased the planet's habitability.

Geomagnetic variation consists of quiet variation, which is regular in appearance and mostly of solar electromagnetic radiation origin, and geomagnetic disturbance, which is irregular in appearance and mostly driven by the solar wind. The purpose of the Kp index, or Kp for short, is to monitor subauroral geomagnetic disturbance on a global scale. Bartels (1949) introduced the standardized Ks and the planetary Kp indices (see also Bartels, 1957aBartels, , 1957bSiebert & Meyer, 1996), which are derived from observatory-specific three-hourly K indices (Bartels, 1938(Bartels, , 1939Bartels et al., , 1940. The methodology to determine Ks and Kp indices is based on earlier indices, namely the global Km index and the reduced Kr and global Kw indices (Bartels et al., 1940). The K index, for which is an early and excellent description in English, is defined as a quasi-logarithmic measure, ranging in steps of 1 from 0 to 9, of the range of geomagnetic disturbance at a geomagnetic observatory in a three-hourly UT interval (00-03, 03-06, …, 21-24). Geomagnetic disturbance is also denoted as K-variation. The concept of K-variation, also referred to as geomagnetic activity or disturbance, predates the discovery of the solar wind and historically, K-variation was seen as the effect of 'solar particle radiation' (e.g. Bartels, 1957a). Siebert (1971) and Siebert and Meyer (1996) use this definition: "K-variations are all irregular disturbances of the geomagnetic field caused by solar particle radiation within the 3 h interval concerned. All other regular and irregular disturbances are non-K-variations. Geomagnetic activity is the occurrence of K-variations." We regard geomagnetic disturbance that is instantaneously driven by the solar wind as K-variation.The sum of the K-variation and its counterpart, the non-K-variation, equals the measured geomagnetic field variation at a geomagnetic observatory. K-variation includes geomagnetic pulsations, bays or substorms, sudden commencements, geomagnetic storms (with the exception of the recovery phase, see below) and other geomagnetic disturbance from fast changes in the ring-current and other magnetospheric and ionospheric currents. The non-K-variation includes phenomena related to energetic electromagnetic solar radiation (EUV, X-ray) like the daily solar and lunar quiet variation Yamazaki & Maute, 2017) and the rare solar flare effects (SFE;Curto & Gaya-Piqué, 2009;Veldkamp & van Sabben, 1960). However, some phenomena that are related to the solar wind also contribute to the non-K-variation because of their regular appearance. Examples are the quiet-time magnetospheric fields of the tail current, the magnetopause current and the ring current that appear as diurnal variation of the geomagnetic field at a point rotating with the Earth (e.g., Maus & Lühr, 2005). Another example is the slow decay of the ring current field in the recovery phase of a geomagnetic storm (e.g., Kamide & Maltsev, 2007). While the ring current field is driven by the solar wind, its decay in the recovery phase i...