A5003872430- Astro and Planetary Science
- Planetary Science and Exploration
- Astrophysics and Star Formation Studies
- Isotope Analysis in Ecology
- Stellar, planetary, and galactic studies
- Space Exploration and Technology
- Laser-induced spectroscopy and plasma
- Space Satellite Systems and Control
- Geology and Paleoclimatology Research
- Geological and Geochemical Analysis
- Nuclear Physics and Applications
- Spacecraft and Cryogenic Technologies
- High-Velocity Impact and Material Behavior
- High-pressure geophysics and materials
- Ion-surface interactions and analysis
- Aerogels and thermal insulation
- Space exploration and regulation
- Geomagnetism and Paleomagnetism Studies
- Methane Hydrates and Related Phenomena
- Geochemistry and Geologic Mapping
- Electron and X-Ray Spectroscopy Techniques
- Mass Spectrometry Techniques and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Integrated Circuits and Semiconductor Failure Analysis
- Spacecraft Design and Technology
Natural History Museum
2012-2024
University of Kent
2008-2024
German Oceanographic Museum
2013-2017
University of California, Los Angeles
2015
Bellingham Technical College
2015
American Museum of Natural History
2005-2014
British Museum
2014
Lawrence Berkeley National Laboratory
2009-2010
Lawrence Livermore National Laboratory
2006-2008
University of California, Davis
2008
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 bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by Stardust spacecraft appear be weakly constructed mixtures nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, metal, and accessory phases. very wide range olivine low-Ca pyroxene compositions in requires a formation conditions, probably reflecting different locations protoplanetary disk. restricted compositional ranges for absence hydrous phases...
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...
Particles emanating from comet 81P/Wild 2 collided with the Stardust spacecraft at 6.1 kilometers per second, producing hypervelocity impact features on collector surfaces that were returned to Earth. The morphologies of these surprisingly diverse created by particles varying dense mineral grains loosely bound, polymineralic aggregates ranging tens nanometers hundreds micrometers in size. cumulative size distribution Wild dust is shallower than Halley, yet steeper Grigg-Skjellerup.
The Stardust mission returned the first sample of a known outer solar system body, comet 81P/Wild 2, to Earth. was expected resemble chondritic porous interplanetary dust particles because many, and possibly all, such are derived from comets. Here, we report that most abundant recognizable silicate materials in appear be absent sample, indicating indigenous nebula material is probably rare 2. Instead, resembles meteorites asteroid belt, composed mostly inner materials. This surprising...
We measured the elemental compositions of material from 23 particles in aerogel and residue seven craters aluminum foil that was collected during passage Stardust spacecraft through coma comet 81P/Wild 2. These are chemically heterogeneous at largest size scale analyzed (â¼180 ng). The mean composition this Wild 2 is consistent with CI meteorite composition, which thought to represent bulk solar system, for elements Mg, Si, Mn, Fe, Ni 35%, Ca Ti 60%. Cu, Zn, Ga appear enriched material,...
Seven particles captured by the Stardust Interstellar Dust Collector and returned to Earth for laboratory analysis have features consistent with an origin in contemporary interstellar dust stream. More than 50 spacecraft debris were also identified. The candidates are readily distinguished from impacts on basis of elemental composition and/or impact trajectory. seven candidate diverse composition, crystal structure, size. presence crystalline grains multiple iron-bearing phases, including...
Infrared spectra of material captured from comet 81P/Wild 2 by the Stardust spacecraft reveal indigenous aliphatic hydrocarbons similar to those in interplanetary dust particles thought be derived comets, but with longer chain lengths than observed diffuse interstellar medium. Similarly, samples contain abundant amorphous silicates addition crystalline such as olivine and pyroxene. The presence Wild is consistent mixing solar system matter. No hydrous or carbonate minerals were detected,...
Abstract— We compare the observed composition ranges of olivine, pyroxene, and Fe‐Ni sulfides in Wild 2 grains with those from chondritic interplanetary dust particles (IDPs) chondrite classes to explore whether these data suggest affinities known hydrous materials particular. olivine has an extremely wide range, Fa 0–96 , a pronounced frequency peak at 1 . The range displayed by low‐calcium pyroxene is also very extensive, Fs 48 0 significant centered 5 These are as broad or broader than...
Abstract— The cometary tray of the NASA Stardust spacecraft's aerogel collector was examined to study dust captured during 2004 flyby comet 81P/Wild 2. An optical scan entire surface revealed 256 impact features in (width >100 μm). Twenty blocks (out a total 132) were removed from for higher resolution and 186 tracks observed (track length >50 μm width >8 classified into three types based on their morphology. Laboratory calibrations conducted that reproduced all types. This work...
Abstract— Modal abundances of Ca,Al‐rich inclusions (CAIs) are poorly known and reported data scatter across large ranges. CAIs Poisson distributed, if only small areas (<1000 mm 2 ) studied, the probably not representative true CAI modal abundances, explaining their in a single chondrite group. We combine our own set, present complete list carbonaceous chondrites. This includes (in area%): CV: 2.98, CM: 1.21, Acfer 094: 1.12, CO: 0.99, CK/CV (Ningqiang Dar al Gani [DaG] 055): 0.77, CK:...
Bulk chondritic meteorites and terrestrial planets show a monotonic depletion in moderately volatile elements relative to the Sun's photosphere CI carbonaceous chondrites. Although was most fundamental chemical process affecting inner solar nebula, debate continues as its cause. Carbonaceous chondrites are primitive rocks available us, fine-grained, volatile-rich matrix is component these rocks. Several models posit pristine matrix, with uniform CI-like chemistry across different chondrite...
Abstract— As the solar system formed, it inherited and perpetuated a rich organic chemistry, molecular products of which are preserved in ancient extraterrestrial objects such as carbonaceous chondrites. These organic‐rich meteorites provide valuable tangible record chemical steps taken towards origin life early system. Chondritic matter is present inorganic meteorite matrix which, CM CI chondrites, contains evidence alteration by liquid water on parent asteroid. An unanswered fundamental...
Aerogel is an ultra-low-density material that can be used to capture small particles incident upon it at speeds in excess of 1 km s −1 . This permits cosmic dust space where the high usually result destructive impact events. The performance aerogel laboratory tests described. Completely intact rare; most studies show between 10% 100% particle's mass captured. However, all cases unaltered domains were found captured up 6 or 7 Several analytic techniques applied situ aerogel, yielding data on...
Abstract We report a petrographic and mineralogical survey of Paris, new CM chondrite considered to be the least‐altered identified so far (Hewins et al. ). Compared other s, Paris exhibits (1) higher concentration Fe‐Ni metal beads, with nickel contents in range 4.1–8.1 wt%; (2) systematic presence thin lamellae tiny blebs pentlandite pyrrhotite grains; (3) ubiquitous tochilinite/cronstedtite associations FeO/SiO 2 S/SiO ratios. In addition, shows highest trapped 36 Ar reported for...
Abstract– The fluence of dust particles <10 μm in diameter was recorded by impacts on aluminum foil the NASA Stardust spacecraft during a close flyby comet 81P/Wild 2 2004. Initial interpretation craters for impactor particle dimensions and mass based upon laboratory experimental simulations using projectiles less than >10 resulting linear relationship projectile to crater extrapolated smaller sizes. We now describe new calibration program firing very small monodisperse silica (470...
Abstract– The majority of meteorite impacts occur at oblique incidence angles. However, many the effects obliquity on impact crater size and morphology are poorly understood. Laboratory experiments numerical models have shown that decreases with angle, along‐range profile becomes asymmetric low angles, below a certain threshold angle planform elliptical. Experimental results approximately constant velocity suggest elliptical depends target material properties. Herein, we test hypothesis for...
The magmatic garnet of seven granitic NYF (niobium–yttrium–fluorine-enriched) pegmatites from the Froland and Evje–Iveland areas in southern Norway were studied with respect to their major- trace-element composition intracrystalline distribution major minor elements. increasing average MnO/(FeO + MnO) values grains investigated reflect fractionation abyssal heavy REE muscovite rare-element pegmatites. At a crystal scale, MnO/(MnO FeO) show various trends controlled by coexisting...
Abstract— Aluminum foils of the Stardust cometary dust collector are peppered with impact features a wide range sizes and shapes. By comparison to laboratory shots known particle dimensions density, using same velocity incidence geometry as Wild 2 encounter, we can derive size mass grains. Using scanning electron microscopy (SEM) foil samples (both flown on mission impacted in laboratory) have recognized feature shapes from which interpret density internal structure. We documented...
Dar al Gani (DaG) 400, Meteorite Hills (MET) 01210, Pecora Escarpment (PCA) 02007, and MacAlpine (MAC) 88104/88105 are lunar regolith breccia meteorites that provide sampling of the surface from regions Moon were not visited by US Apollo or Soviet Luna sample return missions. They contain a heterogeneous clast population range typical lithologies. DaG PCA MAC primarily feldspathic in nature, MET 01210 is composed mare basalt material mixed with lesser amount material. Here we present...
Abstract— In January 2006, the Stardust mission successfully returned dust samples from tail of comet 81P/Wild 2 in two principal collection media, low‐density silica aerogel and Al foil. While hypervelocity impacts at encounter velocity 6.1 km/s into foils are generally highly disruptive for natural, silicate‐dominated impactors, previous studies have shown that many craters retain sufficient residue to allow a determination elemental isotopic compositions original projectile. We used...
The lunar magma ocean model is a well-established theory of the early evolution Moon. By this model, Moon was initially largely molten and anorthositic crust that now covers much surface directly crystallized from enormous source. We are undertaking study geochemical characteristics anorthosites meteorites to test model. Rare earth other element abundances have been measured in situ relict anorthosite clasts two feldspathic meteorites: Dhofar 908 081. rare elements were present approximately...