A5036900042- Astro and Planetary Science
- Planetary Science and Exploration
- earthquake and tectonic studies
- Spacecraft and Cryogenic Technologies
- High-pressure geophysics and materials
- Landslides and related hazards
- Isotope Analysis in Ecology
- Geological and Geochemical Analysis
- Rock Mechanics and Modeling
- Space Exploration and Technology
- Space Satellite Systems and Control
- Gamma-ray bursts and supernovae
- Geotechnical and Geomechanical Engineering
- Spaceflight effects on biology
- Earthquake Detection and Analysis
- Marine and environmental studies
- Space Science and Extraterrestrial Life
- Geology and Paleoclimatology Research
- Nuclear Physics and Applications
- Methane Hydrates and Related Phenomena
- Science Education and Perceptions
- Building materials and conservation
- Climate change and permafrost
- Elbow and Forearm Trauma Treatment
- Pulsars and Gravitational Waves Research
Planetary Science Institute
2012-2024
Jet Propulsion Laboratory
2017-2021
University of Arizona
2011-2015
Ames Research Center
2009-2010
Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances particle ejection from the surface (101955) Bennu, demonstrating it is an active asteroid. The events were imaged by OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) spacecraft. For three largest observed events, we estimated ejected velocities sizes, event times, source regions, energies. also determined trajectories photometric properties...
Heterogeneous thermal properties of Bennu are due primarily to spatial mixing two boulder types with differing strengths.
Abstract Thermomechanical processes such as fatigue and shock have been suggested to cause contribute rock breakdown on Earth, other planetary bodies, particularly airless bodies in the inner solar system. In this study, we modeled grain‐scale stresses induced by diurnal temperature variations simple microstructures made of pyroxene plagioclase various system bodies. We found that a heterogeneous microstructure Moon experiences peak tensile order 100 MPa. The are controlled coefficient...
Visible-wavelength color and reflectance provide information about the geologic history of planetary surfaces. Here we present multispectral images (0.44 to 0.89 micrometers) near-Earth asteroid (101955) Bennu. The surface has variable colors overlain on a moderately blue global terrain. Two primary boulder types are distinguishable by their texture. Space weathering Bennu materials does not simply progress from red (or vice versa). Instead, freshly exposed, redder surfaces initially...
Abstract Rock breakdown due to diurnal thermal cycling has been hypothesized drive boulder degradation and regolith production on airless bodies. Numerous studies have invoked its importance in driving landscape evolution, yet morphological features produced by fracture processes never definitively observed an body, or any surface where other weathering mechanisms may be ruled out. The Origins, Spectral Interpretation, Resource Identification, Security–Regolith Explorer (OSIRIS-REx) mission...
Abstract The exploration of near‐Earth asteroids has revealed dynamic surfaces characterized by mobile, unconsolidated material that responds to local geophysical gradients, resulting in distinct morphologies and boulder distributions. OSIRIS‐REx (Origins, Spectral Interpretation, Resource Identification, Security‐Regolith Explorer) mission confirmed asteroid (101955) Bennu is a rubble pile with an surface dominated boulders. In this work, we documented indicative mass movement on assessed...
Abstract We analyze the trajectories of 313 particles seen in near‐Bennu environment between December 2018 and September 2019. Of these, 65% follow suborbital trajectories, 20% undergo more than one orbital revolution around asteroid, 15% directly escape on hyperbolic trajectories. The median lifetime these is ∼6 hr. are sensitive to Bennu's gravitational field, which allows us reliably estimate spherical harmonic coefficients through degree 8 resolve nonuniform mass distribution 3....
Many boulders on (101955) Bennu, a near-Earth rubble pile asteroid, show signs of in situ disaggregation and exfoliation, indicating that thermal fatigue plays an important role its landscape evolution. Observations particle ejections from surface also it to be active though the driving mechanism these events is yet determined. Exfoliation has been shown mobilize disaggregated particles terrestrial environments, suggesting may capable ejecting material Bennu's surface. We investigate nature...
We manually mapped particles ranging in longest axis from 0.3 cm to 95 m on (101955) Bennu for the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) asteroid sample return mission. This enabled mission identify candidate collection sites shed light processes that have shaped surface of this rubble-pile asteroid. Building a global survey particles, we used higher-resolution data regional observations calculate particle size-frequency...
Thermal stress weathering may play a role in the evolution of terrestrial‐planet landscapes, particularly those without atmospheres, by contributing to rock breakdown, regolith production, and crater degradation. Damage occurs form microscopic cracks that result from thermal cycle or shock. Terrestrial studies typically evaluate efficacy this process measuring rate surface temperature change (dT/dt), using damage threshold 2 K/min. While extent is unknown, we investigate its relative...
The origins of fractures in Martian boulders are unknown. Here, using Mars Exploration Rover 3D data products, we obtain orientation measurements for 1,857 cracks visible 1,573 rocks along the Spirit traverse and find that rock oriented statistically preferred directions similar to those compiled herein Earth found mid-latitude deserts. We suggest directional cracking occurs due preferential propagation microfractures favourably with respect repeating geometries diurnal peaks sun-induced...
This paper summarizes the evidence for optical effects of space weathering, as well properties surface that control changes, on asteroid (101955) Bennu. First, we set stage by briefly reviewing what was known about weathering low-albedo materials from telescopic surveys, laboratory simulations, and sample return analysis. We then look at nature Bennu recent spacecraft imaging spectroscopy observations, including visible to near-infrared thermal infrared wavelengths, followed other...
Asteroid (101955) Bennu, a near-Earth object with primitive carbonaceous chondrite-like composition, was observed by the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft to undergo multiple particle ejection events near perihelion between December 2018 February 2019. The three largest during this period, which all occurred 3.5 6 hr after local noon, placed numerous particles <10 cm on temporary orbits around Bennu. Here we...
Ice sintering is a form of metamorphism that drives the microstructural evolution an aggregate grains through surface and volume diffusion. This leads to increase in grain-to-grain contact area ("neck") density over time, resulting its strength, porosity, thermal conductivity, other properties. process plays important role icy planetary surfaces, though rate nature are not well constrained. In this study, we explore model Swinkels Ashby (1981), assess extent which it can be used quantify...
Abstract The finding by the OSIRIS‐REx (Origins, Spectral Interpretation, Resource Identification, and Security‐Regolith Explorer) mission that its target (101955) Bennu is an active asteroid has raised questions as to whether observed particle ejection events are driven temperature. To investigate sublimation of water ice rock thermal fracture possible temperature‐driven causes, we modeled global temperatures searched for correlations with identified points on surface. We computed Advanced...
Abstract In arid environments, thermal oscillations are an important source of rock weathering. Measurements temperature have been made on the surface rocks in a desert environment at sampling interval 0·375 s, with simultaneous measurements wind speed, air temperature, and incoming shortwave radiation. Over timescales hours, was determined primarily by radiation while rapid variations, high dT/dt , intervals seconds or less, were speed. The maximum values change time spent above 2°C min −1...
Abstract The sample of asteroid (101955) Bennu was collected from the Nightingale site by Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer spacecraft arrived on Earth 24 September 2023. To better understand Bennu's parent body, we identified boulders over 2 m in diameter around region analyzed normal albedo, morphology, surface roughness. We found that can be separated into two groups based four using morphology including angularity, texture, presence...
Vegetation bands are periodic of vegetation, separated by interband spaces devoid oriented parallel to the topographic contour in some gently sloping arid semiarid environments. Models vegetation band formation attribute their positive feedbacks among density, soil porosity/permeability, and infiltration rates. Here we present an alternative model based on field measurements at our study sites southern Nevada. In this model, between form because mounds beneath detain water upslope from...