A5054666787- Astro and Planetary Science
- Geological and Geochemical Analysis
- Planetary Science and Exploration
- Geology and Paleoclimatology Research
- High-pressure geophysics and materials
- Isotope Analysis in Ecology
- Geochemistry and Elemental Analysis
- earthquake and tectonic studies
- Paleontology and Stratigraphy of Fossils
- Geomagnetism and Paleomagnetism Studies
- Stellar, planetary, and galactic studies
- Space Exploration and Technology
- Geochemistry and Geologic Mapping
- Nuclear Physics and Applications
- Astrophysics and Star Formation Studies
- Methane Hydrates and Related Phenomena
- Hydrocarbon exploration and reservoir analysis
- Marine and environmental studies
- Geological Studies and Exploration
- Astronomical and nuclear sciences
- Radioactive element chemistry and processing
- Astronomy and Astrophysical Research
- Spacecraft and Cryogenic Technologies
- Gamma-ray bursts and supernovae
- High-Velocity Impact and Material Behavior
Planetary Science Institute
2015-2024
Harvard University
2015-2024
Harvard University Press
2011-2024
Lawrence Livermore National Laboratory
2006-2020
University of California, Davis
2020
Sandia National Laboratories
2020
California Institute of Technology
1978-2020
Charles River Laboratories (Netherlands)
2018
John Wiley & Sons (United States)
2018
University of Copenhagen
2015
Research Article| September 01, 1991 Chicxulub Crater: A possible Cretaceous/Tertiary boundary impact crater on the Yucatán Peninsula, Mexico Alan R. Hildebrand; Hildebrand 1Department of Planetary Sciences, University Arizona, Tucson, Arizona 85721 Search for other works by this author on: GSW Google Scholar Glen T. Penfield; Penfield 2Aerogravity Division, Carson Services Inc., 32A Blooming Road, Perkasie, Pennsylvania 18944 David A. Kring; Kring Mark Pilkington; Pilkington 3Geophysics...
The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. preliminary examination these samples shows that the nonvolatile portion is an unequilibrated assortment materials have both presolar solar system origin. contains abundance silicate grains are much larger than predictions interstellar grain models, many high-temperature minerals appear formed in inner regions nebula. Their presence a proves formation included...
The radii and orbital periods of 4,000+ confirmed/candidate exoplanets have been precisely measured by the Kepler mission. show a bimodal distribution, with two peaks corresponding to smaller planets (likely rocky) larger intermediate-size planets, respectively. While only masses orbiting brightest stars can be determined ground-based spectroscopic observations, these observations allow calculation their average densities placing constraints on bulk compositions internal structures. However,...
Mantle and crust evolution is discussed in terms of two simple transport models. In model I, continents ( j = 3) are derived by melt extraction over the history earth from undepleted mantle 1), residue forms a depleted 2), which today source mid‐ocean ridge basalts. II, new additions to reservoir 2, becomes more through time repeated melts. Transport equations were solved for stable s , radioactive r daughter d isotopes arbitrary mass growth curves M (τ). For both models isotopic composition...
Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild 2 particle fragments; however, extreme anomalies rare, indicating that the is not a pristine aggregate of presolar materials. Nonterrestrial nitrogen neon isotope ratios suggest indigenous organic matter highly volatile materials were successfully collected. Except for single 17 O-enriched circumstellar stardust grain, silicate oxide minerals have consistent with solar system origin. One...
ABSTRACT Several small dense exoplanets are now known, inviting comparisons to Earth and Venus. Such require translating their masses sizes composition models of evolved multi-layer interior planets. theoretical rely on our understanding the Earth’s interior, as well independently derived equations state, but so far have not involved direct extrapolations from seismic model: Preliminary Reference Model (PREM). To facilitate more detailed compositional between Earth, we derive here a...
Two Sm‐Nd internal isochrons for pyroxene gabbros of the Bay Islands Ophiolite Complex give well‐defined ages 508 ± 6 m.y. and 501 13 with initial 143 Nd/ 144 Nd ε = +7.7 ∓ 0.1 +7.5 0.2, respectively. Total rock samples from pillow basalts, sheeted dikes, trondhjemites, hornblende gabbros, an orthopyroxenite layer harzburgite in range +6.5 to +8.1 average value +7.6. The 87 Sr/ 86 Sr obtained on a pyroxenegabbro is −19.3 0.3, which typical oceanic samples. However, within different phases...
▪ Abstract The Earth has a radiogenic W-isotopic composition compared to chondrites, demonstrating that it formed while 182 Hf (half-life 9 Myr) was extant in and decaying W. This implies underwent early rapid accretion core formation, with most of the accumulation occurring ∼10 Myr, concluding approximately 30 Myr after origin Solar System. Hf-W data for lunar samples can be reconciled major Moon-forming impact terminated terrestrial process ∼30 suggestion proto-Earth impactor mass ratio...