T. J. McCoy
A5027513521- Astro and Planetary Science
- Planetary Science and Exploration
- Isotope Analysis in Ecology
- Geological and Geochemical Analysis
- High-pressure geophysics and materials
- Geology and Paleoclimatology Research
- Nuclear Physics and Applications
- Space Exploration and Technology
- Paleontology and Stratigraphy of Fossils
- Geochemistry and Geologic Mapping
- Geomagnetism and Paleomagnetism Studies
- Hydrocarbon exploration and reservoir analysis
- Stellar, planetary, and galactic studies
- Space Science and Extraterrestrial Life
- Gamma-ray bursts and supernovae
- Spacecraft and Cryogenic Technologies
- Laser-induced spectroscopy and plasma
- Marine and environmental studies
- earthquake and tectonic studies
- Archaeology and ancient environmental studies
- Mineralogy and Gemology Studies
- Geological and Geophysical Studies
- Particle Detector Development and Performance
- Astronomical and nuclear sciences
- Geochemistry and Elemental Analysis
National Museum of Natural History
2016-2025
Smithsonian Institution
2016-2025
Sanofi (United States)
2022
Virginia Tech
2021
University of Oxford
2018
University of Arizona
2008-2017
Chevron (United States)
2014
Armstrong Flight Research Center
2012
Illinois State University
2010
Johnson Space Center
1992-2008
The mineralogy of terrestrial planets evolves as a consequence range physical, chemical, and biological processes. In pre-stellar molecular clouds, widely dispersed microscopic dust particles contain approximately dozen refractory minerals that represent the starting point planetary mineral evolution. Gravitational clumping into protoplanetary disk, star formation, resultant heating in stellar nebula produce primary constituents chondritic meteorites, including chondrules calcium-aluminum...
The Dawn spacecraft targeted 4 Vesta, believed to be a remnant intact protoplanet from the earliest epoch of solar system formation, based on analyses howardite-eucrite-diogenite (HED) meteorites that indicate differentiated parent body. observations reveal giant basin at Vesta's south pole, whose excavation was sufficient produce Vesta-family asteroids (Vestoids) and HED meteorites. spatially resolved mineralogy surface reflects composition meteorites, confirming formation crust by melting...
Mineral deposits on the martian surface can elucidate ancient environmental conditions planet. Opaline silica (as much as 91 weight percent SiO2) have been found in association with volcanic materials by Mars rover Spirit. The are present both light-toned soils and bedrock. We interpret these to formed under hydrothermal therefore be strong indicators of a former aqueous environment. This discovery is important for understanding past habitability because environments Earth support thriving...
X-ray fluorescence spectra obtained by the MESSENGER spacecraft orbiting Mercury indicate that planet's surface differs in composition from those of other terrestrial planets. Relatively high Mg/Si and low Al/Si Ca/Si ratios rule out a lunarlike feldspar-rich crust. The sulfur abundance is at least 10 times higher than silicate portion Earth or Moon, this observation, together with Fe abundance, supports view formed highly reduced precursor materials, perhaps akin to enstatite chondrite...
The MESSENGER Gamma-Ray Spectrometer measured the average surface abundances of radioactive elements potassium (K, 1150 ± 220 parts per million), thorium (Th, 60 billion), and uranium (U, 90 20 billion) in Mercury's northern hemisphere. abundance moderately volatile element K, relative to Th U, is inconsistent with physical models for formation Mercury requiring extreme heating planet or its precursor materials, supports from volatile-containing material comparable chondritic meteorites....
Abstract The recent determination of the gravity field Mercury and new Earth‐based radar observations planet's spin state afford opportunity to explore Mercury's internal structure. These provide estimates two measures radial mass distribution Mercury: normalized polar moment inertia fractional solid portion planet overlying liquid core. Employing Monte Carlo techniques, we calculate several million models density structure consistent with its radius bulk constrained by these parameters. We...
Using Dawn's Gamma Ray and Neutron Detector, we tested models of Vesta's evolution based on studies howardite, eucrite, diogenite (HED) meteorites. Global Fe/O Fe/Si ratios are consistent with HED compositions. measurements confirm that a thick, diogenitic lower crust is exposed in the Rheasilvia basin, which global magmatic differentiation. regolith contains substantial amounts hydrogen. The highest hydrogen concentrations coincide older, low-albedo regions near equator, where water ice...
We present the analysis of 205 spatially resolved measurements surface composition Mercury from MESSENGER's X‐Ray Spectrometer. The footprints these are categorized according to geological terrain. Northern smooth plains deposits and interior Caloris basin differ compositionally older terrain on Mercury. generally has higher Mg/Si, S/Si, Ca/Si ratios, a lower Al/Si ratio than plains. Mercury's mineralogy is likely dominated by high‐Mg mafic minerals (e.g., enstatite), plagioclase feldspar,...
Abstract On September 24, 2023, NASA's OSIRIS‐REx mission dropped a capsule to Earth containing ~120 g of pristine carbonaceous regolith from Bennu. We describe the delivery and initial allocation this asteroid sample introduce its bulk physical, chemical, mineralogical properties early analyses. The is very dark overall, with higher‐reflectance inclusions particles interspersed. Particle sizes range submicron dust stone ~3.5 cm long. Millimeter‐scale larger stones typically have hummocky or...
Abstract Evaporation or freezing of water-rich fluids with dilute concentrations dissolved salts can produce brines, as observed in closed basins on Earth 1 and detected by remote sensing icy bodies the outer Solar System 2,3 . The mineralogical evolution these brines is well understood regard to terrestrial environments 4 , but poorly constrained for extraterrestrial systems owing a lack direct sampling. Here we report occurrence salt minerals samples asteroid (101955) Bennu returned...
Organic matter in meteorites reveals clues about early Solar System chemistry and the origin of molecules important to life, but terrestrial exposure complicates interpretation. Samples returned from B-type asteroid Bennu by Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer mission enabled us study pristine carbonaceous astromaterial without uncontrolled Earth's biosphere. Here we show that samples are volatile rich, with more carbon, nitrogen ammonia than...
The Mössbauer (MB) spectrometer on Opportunity measured the Fe oxidation state, identified Fe‐bearing phases, and relative abundances of among those phases at Meridiani Planum, Mars. Eight were identified: jarosite (K,Na,H 3 O)(Fe,Al)(OH) 6 (SO 4 ) 2 , hematite, olivine, pyroxene, magnetite, nanophase ferric oxides (npOx), an unassigned phase, metallic (kamacite). Burns Formation outcrop rocks consist hematite‐rich spherules dispersed throughout S‐rich rock that has nearly constant...
MESSENGER from Mercury The spacecraft passed by in October 2008, what was the second of three fly-bys before it settles into planet's orbit 2011. Another visited mid-1970s, which mapped 45% surface. Now, after MESSENGER, only 10% Mercury's surface remains to be imaged up close. Denevi et al. (p. 613 ) use this near-global data look at mechanisms that shaped crust, likely formed eruption magmas different compositions over a long period time. Like Moon, is dotted with impact craters. Watters...
Geochemical diversity of rocks and soils has been discovered by the Alpha Particle X‐Ray Spectrometer (APXS) during Spirit's journey over Husband Hill down into Inner Basin from sol 470 to 1368. The APXS continues operate nominally with no changes in calibration or spectral degradation course mission. Germanium added Spirit data set confirmation that it occurs at elevated levels many around Home Plate. Twelve new rock classes two soil have identified landing site since on basis geochemistry....
Orbital gamma‐ray measurements obtained by the MESSENGER spacecraft have been analyzed to determine abundances of major elements Al, Ca, S, Fe, and Na on surface Mercury. The Si abundance was determined used normalize those other reported elements. analysis provides first estimate 2.9 ± 0.1 wt% for this element Mercury's surface. elemental results (S/Si = 0.092 0.015, Ca/Si 0.24 0.05, Fe/Si 0.077 0.013) are consistent with previously X‐Ray Spectrometer, including high sulfur low iron...
Home Plate is a layered plateau in Gusev crater on Mars. It composed of clastic rocks moderately altered alkali basalt composition, enriched some highly volatile elements. A coarsegrained lower unit lies under finer-grained upper unit. Textural observations indicate that the strata were emplaced an explosive event, and geochemical considerations favor volcanic origin over impact origin. The likely represents accumulation pyroclastic materials, whereas may represent eolian reworking same materials.
Spirit's Mössbauer (MB) instrument determined the Fe mineralogy and oxidation state of 71 rocks 43 soils during its exploration Gusev plains Columbia Hills (West Spur, Husband Hill, Haskin Ridge, northern Inner Basin, Home Plate) on Mars. The are predominantly float soil derived from olivine basalts. Outcrops at West Spur Hill have experienced pervasive aqueous alteration as indicated by presence goethite. Olivine‐rich outcrops in a possible mafic/ultramafic horizon present Ridge. Relatively...
Irvine, Backstay, and Wishstone are the type specimens for three classes of fine‐grained or fragmental, relatively unaltered rocks with distinctive thermal emission spectra, found as float on flanks Columbia Hills. Chemical analyses indicate that these mildly alkaline basalt, trachybasalt, tephrite, respectively. Their mineralogy consists Na‐ K‐rich feldspar(s), low‐ high‐Ca pyroxenes, ferroan olivine, Fe‐Ti (and possibly Cr) oxides, phosphate, glass. The texture is consistent a pyroclastic...