Magnetic anomalies concentrated near and within Mercury's impact basins: Early mapping and interpretation

Hood, L. L.

doi:10.1002/2016je005048

Cited by 27 publications

(36 citation statements)

References 32 publications

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“…Instead, it possesses very localized magnetic field anomalies. Such anomalies are also found on the Earth (e.g., Lesur et al, ), the Moon (e.g., Purucker & Nicholas, ), and Mercury (Hood, ; Johnson et al, ), but the Martian anomalies are 1 or 2 orders of magnitude more intense than on these bodies.…”

Section: Introductionmentioning

confidence: 89%

A New Model of the Crustal Magnetic Field of Mars Using MGS and MAVEN

et al. 2019

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While devoid of an active magnetic dynamo field today, Mars possesses a remanent magnetic field that may reach several thousand nanoteslas locally. The exact origin and the events that have shaped the crustal magnetization remain largely enigmatic. Three magnetic field data sets from two spacecraft collected over 13 cumulative years have sampled the Martian magnetic field over a range of altitudes from 90 up to 6,000 km: (a) Mars Global Surveyor (MGS) magnetometer (1997–2006), (b) MGS Electron Reflectometer (1999–2006), and (c) Mars Atmosphere and Volatile EvolutioN (MAVEN) magnetometer (2014 to today). In this paper we combine these complementary data sets for the first time to build a new model of the Martian internal magnetic field. This new model improves upon previous ones in several aspects: comprehensive data coverage, refined data selection scheme, modified modeling scheme, discrete‐to‐continuous transformation of the model, and increased model resolution. The new model has a spatial resolution of ∼160 km at the surface, corresponding to spherical harmonic degree 134. It shows small scales and well‐defined features, which can now be associated with geological signatures.

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Section: Introductionmentioning

confidence: 89%

A New Model of the Crustal Magnetic Field of Mars Using MGS and MAVEN

et al. 2019

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“…A valuable data set for investigating crustal magnetism on Mercury was obtained by the NASA MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) Discovery mission during the final year of its existence (Johnson et al, ). Altitude‐normalized maps of the crustal field covering part of one side of the planet (mainly 90 ∘ E to 270 ∘ E and 35 ∘ N to 75 ∘ N) have previously been constructed from low‐altitude magnetometer data using an equivalent source dipole (ESD) technique (Hood, , ; hereafter H15 and H16). Results showed that the strongest crustal field anomalies in this region are concentrated around and within the 1,550‐km‐diameter Caloris impact basin.…”

Section: Introductionmentioning

confidence: 99%

Investigating Sources of Mercury's Crustal Magnetic Field: Further Mapping of MESSENGER Magnetometer Data

et al. 2018

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One hundred six low‐altitude passes of magnetometer data from the last 2 months of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging mission have been applied to produce a map of the crustal magnetic field at a constant altitude of 40 km covering latitudes of 35–75∘ N and longitudes of 270–90∘ E. Some anomalies correlate significantly with impact basins/craters (e.g., Rustaveli and Vyasa), while other basins/craters have no obvious anomalies. A possible interpretation that is consistent with lunar evidence is that some impactors delivered more ferromagnetic Fe–Ni metal to the interior subsurfaces and ejecta fields of the craters/basins that they produced. The amount of metallic iron that could plausibly be delivered is limited by the diameter and mass of an impactor that would yield a crater with observed diameters (e.g., 200 km for Rustaveli). This in turn limits the maximum amplitude of anomalies that could be induced by impactor‐added iron in the present‐day Mercury global field to relatively low values. It is therefore concluded that if impactor‐added iron is the source of the observed crater‐associated anomalies, then they must be almost entirely a consequence of ancient remanent magnetization. A broad magnetic anomaly occurs over the northern rise, a topographically high region with an associated strong free air gravity anomaly. A possible interpretation of the latter anomaly is that an early major impact preconditioned the region for a later mantle uplift event.

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“…The optimal depth of the array for a given spacing of the dipoles is determined by repeating the inversion procedure until a minimum root‐mean‐square (RMS) deviation of the model radial field values from the observed radial field measurements is obtained. For example, a depth of about 20 km for a dipole array with a horizontal spacing of 1°in latitude and 2°in longitude centered at 55°N latitude was found to be optimal using MESSENGER data [ Hood , ]. The derived depth of this equivalent source representation does not imply that the true sources are at this depth.…”

Section: Mapping Methods and Resultsmentioning

confidence: 99%

Magnetic anomalies in the Imbrium and Schrödinger impact basins: Orbital evidence for persistence of the lunar core dynamo into the Imbrian epoch

Hood

Spudis

2016

JGR Planets

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Approximate maps of the lunar crustal magnetic field at low altitudes in the vicinities of the three Imbrian‐aged impact basins, Orientale, Schrödinger, and Imbrium, have been constructed using Lunar Prospector and Kaguya orbital magnetometer data. Detectable anomalies are confirmed to be present well within the rims of Imbrium and Schrödinger. Anomalies in Schrödinger are asymmetrically distributed about the basin center, while a single isolated anomaly is most clearly detected within Imbrium northwest of Timocharis crater. The subsurface within these basins was heated to high temperatures at the time of impact and required long time periods (up to 1 Myr) to cool below the Curie temperature for metallic iron remanence carriers (1043 K). Therefore, consistent with laboratory analyses of returned samples, a steady, long‐lived magnetizing field, i.e., a former core dynamo, is inferred to have existed when these basins formed. The asymmetrical distribution within Schrödinger suggests partial demagnetization by later volcanic activity when the dynamo field was much weaker or nonexistent. However, it remains true that anomalies within Imbrian‐aged basins are much weaker than those within most Nectarian‐aged basins. The virtual absence of anomalies within Orientale where impact melt rocks (the Maunder Formation) are exposed at the surface is difficult to explain unless the dynamo field was much weaker during the Imbrian period.

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Magnetic anomalies concentrated near and within Mercury's impact basins: Early mapping and interpretation

Cited by 27 publications

References 32 publications

A New Model of the Crustal Magnetic Field of Mars Using MGS and MAVEN

A New Model of the Crustal Magnetic Field of Mars Using MGS and MAVEN

Investigating Sources of Mercury's Crustal Magnetic Field: Further Mapping of MESSENGER Magnetometer Data

Magnetic anomalies in the Imbrium and Schrödinger impact basins: Orbital evidence for persistence of the lunar core dynamo into the Imbrian epoch

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