A5031534516- Astro and Planetary Science
- Planetary Science and Exploration
- Space Science and Extraterrestrial Life
- Isotope Analysis in Ecology
- Space Exploration and Technology
- Geology and Paleoclimatology Research
- earthquake and tectonic studies
- Space exploration and regulation
- Geological formations and processes
- Earthquake Detection and Analysis
- Methane Hydrates and Related Phenomena
- Stellar, planetary, and galactic studies
- Seismology and Earthquake Studies
- Spacecraft and Cryogenic Technologies
- Contact Mechanics and Variational Inequalities
- Spacecraft Design and Technology
- Technology Assessment and Management
- Orthopaedic implants and arthroplasty
- Geological and Geophysical Studies
- Adhesion, Friction, and Surface Interactions
- Marine and environmental studies
- High-pressure geophysics and materials
- Scientific Research and Discoveries
- Geomagnetism and Paleomagnetism Studies
- Drilling and Well Engineering
University of Maryland, College Park
2020-2024
Institut Superieur de l'Aeronautique et de l'Espace (ISAE-SUPAERO)
2024
University of Washington
2001
Harborview Medical Center
2001
When the OSIRIS-REx spacecraft pressed its sample collection mechanism into surface of Bennu, it provided a direct test poorly understood near-subsurface physical properties rubble-pile asteroids, which consist rock fragments at rest in microgravity. Here, we find that forces measured by are best modeled as granular bed with near-zero cohesion is half dense bulk asteroid. The low gravity small asteroid such Bennu effectively weakens near subsurface not compressing upper layers, thereby...
Abstract We explore binary asteroid formation by spin-up and rotational disruption considering the NASA DART mission's encounter with Didymos–Dimorphos binary, which was first small visited a spacecraft. Using suite of N -body simulations, we follow gravitational accumulation satellite from meter-sized particles following mass-shedding event rapidly rotating primary. The satellite’s is chaotic, as it undergoes series collisions, mergers, close encounters other moonlets, leading to wide range...
We numerically investigate tidally induced surface refreshing on Apophis during its close approach with Earth within a perigee distance of 5.96 radii April 13, 2029. implement tidal resurfacing model two stages: dynamics modeling the entire body to determine time-varying accelerations and slope profiles felt by each patch 6-h-long closest encounter, DEM track motions grains in localized patches. The measured grain are combined statistically extrapolate 'expected' percentage resurfaced area....
The internal structure of small asteroids (diameter < 1 km) remains poorly known, and recent spacecraft/surface interactions performed by the Osiris-REX Hayabusa2 missions produced unexpected results about their physical properties.What is level macro- micro-porosity? What are cohesive forces? Are bodies stratified, heterogeneous or more homogenous? answers to these questions have strong implications for both long-term evolution planetary defense.Seismology experiments on such objects...
Lead Arthropathy and Systemic Poisoning from an Intraarticular BulletJoseph DeMartini1, Anthony Wilson1, Jerry S. Powell2 Clermont Powell3Audio Available | Share
Abstract Spectral characterization of near-Earth asteroids (NEAs) has revealed a continuum space-weathered states for the surfaces S-complex NEAs, with Q-class an subclass, most closely matching unweathered ordinary chondrite meteorites. Dynamical calculations orbital evolution NEAs that tend to have close encounters terrestrial planets, suggesting planetary tides may play role in refreshing NEA surfaces. However, exact physical mechanism(s) drive resurfacing through tidal and encounter...
Many advancements in planetary science are achieved by seizing upon the opportunity created rare natural events (e.g. comet Shoemaker-Levy 9 Jupiter impact; 1994) and planned physical interactions Deep Impact into Tempel 1; 2005). A forthcoming to seize a “experiment” occurs on April 13, 2029 with unprecedentedly close Earth encounter large 340m asteroid (99942) Apophis. On that date, nature is performing of subjecting body Apophis Earth’s tidal torques as it approaches within 31,000 km...
Abstract We present an approach for the inclusion of nonspherical constituents in high-resolution N -body discrete element method (DEM) simulations. use aggregates composed bonded spheres to model components. Though may be applied more generally, we detail our implementation existing code pkdgrav . It has long been acknowledged that grains confer additional shear strength and resistance flow when compared with spheres. As a result, expect rubble-pile asteroids will also exhibit these...
We explore binary asteroid formation by spin-up and rotational disruption considering the NASA DART mission's encounter with Didymos-Dimorphos binary, which was first small visited a spacecraft. Using suite of $N$-body simulations, we follow gravitational accumulation satellite from meter-sized particles following mass-shedding event rapidly rotating primary. The satellite's is chaotic, as it undergoes series collisions, mergers, close encounters other moonlets, leading to wide range...
Spectral characterization of near-Earth asteroids (NEAs) has revealed a continuum space-weathered states for the surfaces S-complex NEAs, with Q-class an subclass, most closely matching un-weathered ordinary chondrite meteorites. Dynamical calculations orbital evolution NEAs that tend to have close encounters terrestrial planets, suggesting planetary tides may play role in refreshing NEA surfaces. However, exact physical mechanism(s) drive resurfacing through tidal and encounter distance at...
The 2029 close Earth encounter of Near-Earth Asteroid 99942 Apophis presents a unique opportunity to study the dynamics, bulk properties, and interior structure potential rubble-pile asteroid [1]. Numerical models &#8211; including Finite Element Methods (FEM) Discrete (DEM) are essential constrain dynamical outcomes support planned science missions [2, 3].The primary consensus from indicate that most visible physical outcome approach will be change in rotation state [4, 5], pass outside...
Introduction:&#160; The tidal encounter of asteroid Apophis with the Earth in 2029 offers ideal scenario for first in-situ seismic investigation an asteroid. A seismometer can be used to monitor seismicity due forces [1], and other natural sources such as micro-meteoroid impacts or thermal cracks; [2-4]. In addition, a image Apophis&#8217; sub-surface internal structure [2] providing information about asteroid&#8217;s physical properties that is critical planetary defense,...
Introduction:The evolution of rotation rates small asteroids is subjected to mechanisms including (1) The Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect [1]: a thermophysical process that arises from the anisotropic thermal re-radiation absorbed sunlight a&#160;non-axially symmetric surface, resulting in net torque can secularly modify bulk rate. (2) Off-spin-axis collisions by projectile [2]: such change spin state an asteroid through exchange between orbital angular momentum and...
Apophis 2029
&lt;p&gt;Recent sample-return missions to asteroids (101955) Bennu and (162173) Ryugu have revealed their rough surfaces are strewn with regolith particles ranging from millimeters tens of meters in diameter a broad spectrum shapes. Numerical modelers often simulate these kinds bodies as rubble piles composed discrete rock-like material properties. The most models for the past few decades been independent spheres meant represent individual grains that make up surface interior pile....
In 2019, the New Horizons spacecraft flew by Kuiper belt object (486958) Arrokoth, a member of cold classical population in belt. Images returned from flyby reveal that Arrokoth is contact binary composed two distinct lobes joined narrow region (the "neck"). The are roughly similar to oblate spheroids shape and long axis whole body about 35 km [1]. Cold objects like thought be among most primitive bodies our solar system, forming their current positions nebula over 4 Gyr ago remaining nearly...
We numerically investigate tidally induced surface refreshing on Apophis during its close approach with Earth within a perigee distance of 5.96 radii April 13, 2029. implement tidal resurfacing model two stages: dynamics modeling the entire body to determine time-varying accelerations and slope profiles felt by each patch 6-h-long closest encounter, DEM track motions grains in localized patches. The measured grain are combined statistically extrapolate 'expected' percentage resurfaced area....
We present an approach for the inclusion of non-spherical constituents in high-resolution N-body discrete element method (DEM) simulations. use aggregates composed bonded spheres to model components. Though may be applied more generally, we detail our implementation existing code pkdgrav. It has long been acknowledged that grains confer additional shear strength and resistance flow when compared with spheres. As a result, expect rubble-pile asteroids will also exhibit these properties behave...