Showing papers by "Mark A. Wieczorek published in 2023"
TL;DR: The Psyche magnetometer as discussed by the authors measured the magnetic field around the asteroid to search for evidence of remanent magnetization, assuming that the asteroid formed from the core of a differentiated planetesimal.
Abstract: The objective of the Psyche Magnetometry Investigation is to test the hypothesis that asteroid (16) Psyche formed from the core of a differentiated planetesimal. To address this, the Psyche Magnetometer will measure the magnetic field around the asteroid to search for evidence of remanent magnetization. Paleomagnetic measurements of meteorites and dynamo theory indicate that a diversity of planetesimals once generated dynamo magnetic fields in their metallic cores. Likewise, the detection of a strong magnetic moment ( >2×1014Am2 ) at Psyche would likely indicate that the body once generated a core dynamo, implying that it formed by igneous differentiation. The Psyche Magnetometer consists of two three-axis fluxgate Sensor Units (SUs) mounted 0.7 m apart along a 2.15-m long boom and connected to two Electronics Units (EUs) located within the spacecraft bus. The Magnetometer samples at up to 50 Hz, has a range of ±80,000nT , and an instrument noise of 39pTaxis-13σ integrated over 0.1 to 1 Hz. The two pairs of SUs and EUs provide redundancy and enable gradiometry measurements to suppress noise from flight system magnetic fields. The Magnetometer will be powered on soon after launch and acquire data for the full duration of the mission. The ground data system processes the Magnetometer measurements to obtain an estimate of Psyche's dipole moment.
1 citations
TL;DR: In this article , the authors report observations of Rayleigh waves that orbit around Mars up to three times following the S1222a marsquake, and find the largest amplitude signals at 30 and 85 s central period, propagating with distinctly different group velocities of 2.9 and 3.8 km/s.
Abstract: We report observations of Rayleigh waves that orbit around Mars up to three times following the S1222a marsquake. Averaging these signals, we find the largest amplitude signals at 30 and 85 s central period, propagating with distinctly different group velocities of 2.9 and 3.8 km/s, respectively. The group velocities constraining the average crustal thickness beneath the great circle path rule out the majority of previous crustal models of Mars that have a >200 kg/m3 density contrast across the equatorial dichotomy between northern lowlands and southern highlands. We find that the thickness of the Martian crust is 42–56 km on average, and thus thicker than the crusts of the Earth and Moon. Considered with the context of thermal evolution models, a thick Martian crust suggests that the crust must contain 50%–70% of the total heat production to explain present‐day local melt zones in the interior of Mars.
1 citations
DOI•
TL;DR: In this article , the authors proposed an approach based on random matrix theory applied to receiver functions (RFs) to further constrain the subsurface structure of Mars by detecting coherent arrivals in the waveforms.
Abstract: Recent estimates of the crustal thickness of Mars show a bimodal result of either ∼20 or ∼40 km beneath the InSight lander. We propose an approach based on random matrix theory applied to receiver functions (RFs) to further constrain the subsurface structure. Assuming a spiked covariance model for our data, we first use the phase transition properties of the singular value spectrum of random matrices to detect coherent arrivals in the waveforms. Examples from terrestrial data show how the method works in different scenarios. We identify three previously undetected converted arrivals in the InSight data, including the first multiple from a deeper third interface. We then use this information to jointly invert RFs with the absolute S‐wave velocity information in the polarization of body waves. Results show a crustal thickness of 43 ± 5 km beneath the lander with two mid‐crustal interfaces at depths of 8 ± 1 and 21 ± 3 km.
1 citations
TL;DR: Nimmo et al. as discussed by the authors proposed an approach for the first time in the context of space flight, which is based on the Plesa-Collins algorithm. But Plesa and Collins' approach is not suitable for the current state-of-the-art.
Abstract: F. Nimmo1, A.-C. Plesa2, M.A. Wieczorek3, R. Citron4,5, and G.S. Collins6, 1University of California, Santa Cruz (UCSC; Santa Cruz, CA 95060, USA; sgyalay@ucsc.edu), 2German Aerospace Center (DLR; Berlin, Germany), 3Institut de Physique du Globe de Paris (IPGP), Paris Cité, French National Centre for Scientific Research (Paris, 75005 France), 4Massachusetts Institute of Technology (MIT; Cambridge, MA 02139, USA), 5NASA Goddard Space Flight Center (Greenbelt, MD 20771, USA), 6Imperial College London (London, UK).