Examinando por Autor "Wieczorek, Mark A."

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A New Large-Scale Map of the Lunar Crustal Magnetic Field and Its Interpretation
(Advancing Earth and Space Science AGU, 2021-02-23) Hood, L. L.; Torres, C. B.; Oliveira, Joana S.; Wieczorek, Mark A.; Stewart, S. T.; National Aeronautics and Space Administration (NASA)
A new large-scale map of the lunar crustal magnetic field at 30 km altitude covering latitudes from 65°S to 65°N has been produced using high-quality vector magnetometer data from two complementary polar orbital missions, Lunar Prospector and SELENE (Kaguya). The map has characteristics similar to those of previous maps but better resolves the shapes and distribution of weaker anomalies. The strongest group of anomalies is located on the northwest side of the South Pole-Aitken basin approximately antipodal to the Imbrium basin. On the near side, both strong isolated anomalies and weaker elongated anomalies tend to lie along lines oriented radial to Imbrium. These include named anomalies such as Reiner Gamma, Hartwig, Descartes, Abel, and Airy. The statistical significance of this tendency for elongated anomalies is verified by Monte Carlo simulations. Great circle paths determined by end points of elongated anomaly groups and the locations of five individual strong anomalies converge within the inner rim of Imbrium and intersect within the Imbrium antipode zone. Statistically significant evidence for similar alignments northwest of the Orientale basin is also found. The observed distribution of anomalies on the near side and the location of the strongest anomaly group antipodal to Imbrium are consistent with the hypothesis that iron from the Imbrium impactor was mixed into ejecta that was inhomogeneously deposited downrange in groups aligned radial to the basin and concentrated antipodal to the basin.
Acceso Abierto
Constraints on the Spatial Distribution of Lunar Crustal Magnetic Sources From Orbital Magnetic Field Data
(Advancing Earth and Space Science (AGU), 2024-02-14) Oliveira, Joana S.; Vervelidou, Foteini; Wieczorek, Mark A.; Díaz Michelena, Marina; Ministerio de Ciencia e Innovación (MICINN); European Research Council (ERC)
Spacecraft measurements show that the crust of the Moon is heterogeneously magnetized. The sources of these magnetic anomalies are yet not fully understood, with most not being related to known geological structures or processes. Here, we use an inversion methodology that relies on the assumption of unidirectional magnetization, commonly referred to as Parker's method, to elucidate the origin of the magnetic sources by constraining the location and geometry of the underlying magnetization. This method has been used previously to infer the direction of the underlying magnetization but it has not been tested as to whether it can infer the geometry of the source. The performance of the method is here assessed by conducting a variety of tests, using synthetic magnetized bodies of different geometries mimicking the main geological structures potentially magnetized within the lunar crust. Results from our tests show that this method successfully localizes and delineates the two-dimensional surface projection of subsurface three-dimensional magnetized bodies, provided their magnetization is close to unidirectional and the magnetic field data are of sufficient spatial resolution and reasonable signal-to-noise ratio. We applied this inversion method to two different lunar magnetic anomalies, the Mendel-Rydberg impact basin and the Reiner Gamma swirl. For Mendel-Rydberg, our analysis shows that the strongest magnetic sources are located within the basin's inner ring, whereas for Reiner Gamma, the strongest magnetic sources form a narrow dike-like body that emanates from the center of the Marius Hills volcanic complex.
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Initial results from the InSight mission on Mars
(Nature Research Journals, 2020-02-24) Banerdt, W. B.; Smrekar, Suzanne; Banfield, D.; Giardini, D.; Golombek, M.; Johnson, C. L.; Lognonné, P.; Spiga, A.; Spohn, T.; Perrin, C.; Stähler, S.; Antonangeli, D.; Asmar, S.; Beghein, C.; Bowles, N.; Bozdag, E.; Chi, P.; Christensesn, U.; Clinton, J.; Collins, G. S.; Daubar, I.; Dehant, V.; Drilleau, M.; Fillingim, M.; Folkner, W.; García, R. F.; Garvin, J. B.; Grant, J.; Grott, M.; Grygorczuk, J.; Hudson, T.; Irving, J. C. E.; Kargl, G.; Kawamura, T.; Kedar, S.; King, S.; Knapmeyer Endrun, B.; Knapmeyer, M.; Lemmon, M. T.; Lorenz, R.; Maki, Justin N.; Margerin, L.; McLennan, S. M.; Michaut, C.; Mimoun, D.; Mittelholz, A.; Mocquet, A.; Morgan, P.; Mueller, N. T.; Murdoch, N.; Nagihara, S.; Newman, C. E.; Nimmo, F.; Panning, M.; Thomas Pike, W.; Plesa, A. C.; Rodríguez, Sébastien; Rodríguez Manfredi, J. A.; Russell, C. T.; Chmerr, N.; Siegler, M.; Stanley, S.; Stutzmann, E.; Teanby, N.; Tromp, J.; Van Driel, M.; Warner, N.; Weber, R.; Wieczorek, Mark A.; Agence Nationale de la Recherche (ANR); Swiss National Science Foundation (SNSF); Tromp, J. [0000-0002-2742-8299]; Rodríguez, S. [0000-0003-1219-0641]; Lognonné, P. [0000-0002-1014-920X]; Perrin, C. [0000-0002-7200-5682]; Murdoch, N. [0000-0002-9701-4075]; Knapmeyer, M. [0000-0003-0319-2514]; Rodríguez Manfredi, J. A. [0000-0003-0461-9815]; Spiga, A. [0000-0002-6776-6268]; Panning, M. P. [0000-0002-2041-3190]; García, R. [0000-0003-1460-6663]; Johnson, C. [0000-0001-6084-0149]; Stutzmann, E. [0000-0002-4348-7475]; Knapmeyer-Endrun, B. [0000-0003-3309-6785]; Schmerr, N. [0000-0002-3256-1262]; Irving, J. C. E. [0000-0002-0866-8246]; Morgan, P. [0000-0001-8714-4178]; Mueller, N. [0000-0001-9229-8921]; Pike, W. [0000-0002-7660-6231]; Kawamura, T. [0000-0001-5246-5561]; Clinton, J. [0000-0001-8626-2703]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
NASA’s InSight (Interior exploration using Seismic Investigations, Geodesy and Heat Transport) mission landed in Elysium Planitia on Mars on 26 November 2018. It aims to determine the interior structure, composition and thermal state of Mars, as well as constrain present-day seismicity and impact cratering rates. Such information is key to understanding the differentiation and subsequent thermal evolution of Mars, and thus the forces that shape the planet’s surface geology and volatile processes. Here we report an overview of the first ten months of geophysical observations by InSight. As of 30 September 2019, 174 seismic events have been recorded by the lander’s seismometer, including over 20 events of moment magnitude Mw = 3–4. The detections thus far are consistent with tectonic origins, with no impact-induced seismicity yet observed, and indicate a seismically active planet. An assessment of these detections suggests that the frequency of global seismic events below approximately Mw = 3 is similar to that of terrestrial intraplate seismic activity, but there are fewer larger quakes; no quakes exceeding Mw = 4 have been observed. The lander’s other instruments—two cameras, atmospheric pressure, temperature and wind sensors, a magnetometer and a radiometer—have yielded much more than the intended supporting data for seismometer noise characterization: magnetic field measurements indicate a local magnetic field that is ten-times stronger than orbital estimates and meteorological measurements reveal a more dynamic atmosphere than expected, hosting baroclinic and gravity waves and convective vortices. With the mission due to last for an entire Martian year or longer, these results will be built on by further measurements by the InSight lander.
Restringido
Magnetic Anomalies in Five Lunar Impact Basins: Implications for Impactor Trajectories and Inverse Modeling
(Advancing Earth and Space Science AGU, 2020-12-30) Hood, L. L.; Oliveira, Joana S.; Andrews Hanna, J. J.; Wieczorek, Mark A.; Stewart, S. T.; Oliveira, Joana S.; National Aeronautics and Space Administration (NASA)
A recent large-scale map of the lunar crustal magnetic field is examined for the existence of magnetic anomalies internal to ringed impact basins. It is found that, of 25 basins with upper preNectarian and younger ages, 18 contain mapped internal anomalies with amplitudes of at least 1 nT at 30 km altitude. Of these, five are most confidently judged to contain intrinsic anomalies (i.e., anomalies located within the inner basin rims and originating at the times of basin formation): Crisium, Humboldtianum, Mendel-Rydberg, Moscoviense, and Nectaris. Comparing the anomaly distributions with previous numerical simulations of the impact of iron-rich planetesimals to form a large (SPA-sized) basin, inferences are drawn about the likely trajectories of the impactors. Specifically, results suggest that impactor trajectories for these basins were within ∼45° of being vertical and tended to lie on average parallel to the lunar equatorial plane and the ecliptic plane. Inverse modeling of anomalies within these basins yields inferred directions of magnetization that are difficult to reconcile with the axial centered dipole hypothesis for the geometry of the internal lunar dynamo field: Paleomagnetic pole positions are widely scattered and, in agreement with a recent independent study, the two main anomalies within Crisium yield significantly different directions of magnetization.