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R. Bastien

Bio: R. Bastien is an academic researcher. The author has contributed to research in topics: Cosmic dust & Interstellar medium. The author has an hindex of 4, co-authored 11 publications receiving 77 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the trajectories of ISD in the solar system and the distribution of the impact speeds, directions, and flux of the ISD particles on the Stardust Interstellar Dust Collector during the two collection periods of the mission were predicted.
Abstract: On the basis of an interstellar dust model compatible with Ulysses and Galileo observations, we calculate and predict the trajectories of interstellar dust (ISD) in the solar system and the distribution of the impact speeds, directions, and flux of ISD particles on the Stardust Interstellar Dust Collector during the two collection periods of the mission. We find that the expected impact velocities are generally low (less than 10 km per second) for particles with the ratio of the solar radiation pressure force to the solar gravitational force beta greater than 1, and that some of the particles will impact on the cometary side of the collector. If we assume astronomical silicates for particle material and a density of 2 grams per cubic centimeter, and use the Ulysses measurements and the ISD trajectory simulations, we conclude that the total number of (detectable) captured ISD particles may be on the order of 50. In companion papers in this volume, we report the discovery of three interstellar dust candidates in the Stardust aerogel tiles. The impact directions and speeds of these candidates are consistent with those calculated from our ISD propagation model, within the uncertainties of the model and of the observations.

31 citations

Journal ArticleDOI
TL;DR: The Stardust Interstellar Preliminary Examination team analyzed thirteen Al foils from the NASA Stardust interstellar collector tray in order to locate candidate interstellar dust (ISD) grain impacts.
Abstract: The Stardust Interstellar Preliminary Examination team analyzed thirteen Al foils from the NASA Stardust interstellar collector tray in order to locate candidate interstellar dust (ISD) grain impacts. Scanning electron microscope (SEM) images reveal that the foils possess abundant impact crater and crater-like features. Elemental analyses of the crater features, with Auger electron spectroscopy, SEM-based energy dispersive X-ray (EDX) spectroscopy, and scanning transmission electron microscope-based EDX spectroscopy, demonstrate that the majority are either the result of impacting debris fragments from the spacecraft solar panels, or intrinsic defects in the foil. The elemental analyses also reveal that four craters contain residues of a definite extraterrestrial origin, either as interplanetary dust particles or ISD particles. These four craters are designated level 2 interstellar candidates, based on the crater shapes indicative of hypervelocity impacts and the residue compositions inconsistent with spacecraft debris.

22 citations

Proceedings ArticleDOI
15 Apr 2010
TL;DR: In this paper, the authors describe the critical role that synchrotron X-ray and infrared microprobes are playing in the search for interstellar dust in the Stardust Interstellar Dust Collector (SIDC).
Abstract: Here we describe the critical role that synchrotron X-ray and infrared microprobes are playing in the search for interstellar dust in the Stardust Interstellar Dust Collector (SIDC). The samples under examination are submicron particles trapped in low-density aerogel. We have found that the spatial resolution, energy range, and flux capabilities of the FTIR beamlines 1.4.3, ALS, and U2B, NSLS; the XRF microprobes ID13 and ID22NI, ESRF and 2-ID-D, APS; and the STXM beamline 11.0.2, ALS are ideally suited for studying these tiny returned samples. Using nondestructive, coordinated analyses at these microprobes, we have been able to eliminate most candidates as likely samples of interstellar dust. This in itself is a major accomplishment, since the analysis of these tiny samples is technically extremely challenging.

10 citations

23 Mar 2009
TL;DR: The Stardust Interstellar Preliminary Examination (ISPE) as discussed by the authors is a three-year effort to characterize the Stardust interstellar dust collection and collector using non-destructive techniques, which was initiated by Westphal et al. in 2003.
Abstract: The Stardust Interstellar Preliminary Examination (ISPE) is a three-year effort to characterize the Stardust interstellar dust collection and collector using non-destructive techniques. We summarize the status of the ISPE. In January 2006 the Stardust sample return capsule returned to Earth bearing the first solid samples from a primitive solar system body, Comet 81P/Wild2, and a collector dedicated to the capture and return of contemporary interstellar dust. Both collectors were {approx}0.1 m{sup 2} in area and were composed of aerogel tiles (85% of the collecting area) and aluminum foils. The Stardust Interstellar Dust Collector (SIDC) was exposed to the interstellar dust stream for a total exposure factor of 20 m{sup 2}-day during two periods before the cometary encounter. The Stardust Interstellar Preliminary Examination (ISPE) is a three-year effort to characterize the collection using nondestructive techniques. The goals and restrictions of the ISPE are described in Westphal et al. The ISPE consists of six interdependent projects: (1) Candidate identification through automated digital microscopy and a massively distributed, calibrated search; (2) Candidate extraction and photodocumentation; (3) Characterization of candidates through synchrotron-based Fourier-Tranform Infrared Spectroscopy (FTIR), Scanning X-Ray Fluoresence Microscopy (SXRF), and Scanning Transmission X-ray Microscopy (STXM); (4) Search for and analysis of cratersmore » in foils through FESEM scanning, Auger Spectroscopy and synchrotron-based Photoemission Electron Microscopy (PEEM); (5) Modeling of interstellar dust transport in the solar system; and (6) Laboratory simulations of hypervelocity dust impacts into the collecting media.« less

6 citations

01 Mar 2013
TL;DR: Bastien et al. as mentioned in this paper used ER-2 airframe to demonstrate the capability of the ER2 aircraft for the first time in the early 1990s and used it in the development of the Orion spacecraft.
Abstract: POTENTIALLY SAMPLED BY ER-2 AIRCRAFT. R. Bastien, S. Broce, P. Brown, P.J. Burkett, M. Campbell-Brown, D. Frank, D. Gearheart, M. Kapitzke, T. Moes, M. Rodriguez, D. Steel, T. Williams, M. Zolensky. Jacobs Engneering Corp., Houston, TX 77058 (ronbastien@nasa.gov), 2 Computer Sciences Corporation, Dryden, CA, Dept of Physics and Astronomy, University of Western Ontario, London, Ont., Canada N6A 3K7, Centre for Planetary Science and Exploration, University of Western Ontario, London, Ont., Canada, N6A 5B7, UC Santa Cruz, CA, 6 NASA Dryden Flight Research Center, Dryden CA, ARES, NASA Johnson Space Center, Houston, TX.

2 citations


Cited by
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Journal ArticleDOI
05 Aug 2010-Nature
TL;DR: Foldit is described, a multiplayer online game that engages non-scientists in solving hard prediction problems and shows that top-ranked Foldit players excel at solving challenging structure refinement problems in which substantial backbone rearrangements are necessary to achieve the burial of hydrophobic residues.
Abstract: A natural polypeptide chain can fold into a native protein in microseconds, but predicting such stable three-dimensional structure from any given amino-acid sequence and first physical principles remains a formidable computational challenge. Aiming to recruit human visual and strategic powers to the task, Seth Cooper, David Baker and colleagues turned their 'Rosetta' structure-prediction algorithm into an online multiplayer game called Foldit, in which thousands of non-scientists competed and collaborated to produce a rich set of new algorithms and search strategies for protein structure refinement. The work shows that even computationally complex scientific problems can be effectively crowd-sourced using interactive multiplayer games. Predicting the structure of a folded protein from first principles for any given amino-acid sequence remains a formidable computational challenge. To recruit human abilities to the task, these authors turned their Rosetta structure prediction algorithm into an online multiplayer game in which thousands of non-scientists competed and collaborated to produce new algorithms and search strategies for protein structure refinement. This shows that computationally complex problems can be effectively 'crowd-sourced' through interactive multiplayer games. People exert large amounts of problem-solving effort playing computer games. Simple image- and text-recognition tasks have been successfully ‘crowd-sourced’ through games1,2,3, but it is not clear if more complex scientific problems can be solved with human-directed computing. Protein structure prediction is one such problem: locating the biologically relevant native conformation of a protein is a formidable computational challenge given the very large size of the search space. Here we describe Foldit, a multiplayer online game that engages non-scientists in solving hard prediction problems. Foldit players interact with protein structures using direct manipulation tools and user-friendly versions of algorithms from the Rosetta structure prediction methodology4, while they compete and collaborate to optimize the computed energy. We show that top-ranked Foldit players excel at solving challenging structure refinement problems in which substantial backbone rearrangements are necessary to achieve the burial of hydrophobic residues. Players working collaboratively develop a rich assortment of new strategies and algorithms; unlike computational approaches, they explore not only the conformational space but also the space of possible search strategies. The integration of human visual problem-solving and strategy development capabilities with traditional computational algorithms through interactive multiplayer games is a powerful new approach to solving computationally-limited scientific problems.

1,265 citations

Journal ArticleDOI
TL;DR: The rapid social evolution of player-developed folding algorithms that took place in the year following the introduction of tools for players to encode their folding strategies as “recipes” and to share their recipes with other players, who are able to further modify and redistribute them are described.
Abstract: Foldit is a multiplayer online game in which players collaborate and compete to create accurate protein structure models. For specific hard problems, Foldit player solutions can in some cases outperform state-of-the-art computational methods. However, very little is known about how collaborative gameplay produces these results and whether Foldit player strategies can be formalized and structured so that they can be used by computers. To determine whether high performing player strategies could be collectively codified, we augmented the Foldit gameplay mechanics with tools for players to encode their folding strategies as “recipes” and to share their recipes with other players, who are able to further modify and redistribute them. Here we describe the rapid social evolution of player-developed folding algorithms that took place in the year following the introduction of these tools. Players developed over 5,400 different recipes, both by creating new algorithms and by modifying and recombining successful recipes developed by other players. The most successful recipes rapidly spread through the Foldit player population, and two of the recipes became particularly dominant. Examination of the algorithms encoded in these two recipes revealed a striking similarity to an unpublished algorithm developed by scientists over the same period. Benchmark calculations show that the new algorithm independently discovered by scientists and by Foldit players outperforms previously published methods. Thus, online scientific game frameworks have the potential not only to solve hard scientific problems, but also to discover and formalize effective new strategies and algorithms.

477 citations

Journal ArticleDOI
15 Aug 2014-Science
TL;DR: The Stardust Interstellar Dust Collector captured seven particles and returned to Earth for laboratory analysis have features consistent with an origin in the contemporary interstellar dust stream and more than 50 spacecraft debris particles were also identified as discussed by the authors.
Abstract: Seven particles captured by the Stardust Interstellar Dust Collector and returned to Earth for laboratory analysis have features consistent with an origin in the contemporary interstellar dust stream. More than 50 spacecraft debris particles were also identified. The interstellar dust candidates are readily distinguished from debris impacts on the basis of elemental composition and/or impact trajectory. The seven candidate interstellar particles are diverse in elemental composition, crystal structure, and size. The presence of crystalline grains and multiple iron-bearing phases, including sulfide, in some particles indicates that individual interstellar particles diverge from any one representative model of interstellar dust inferred from astronomical observations and theory.

176 citations

Proceedings ArticleDOI
19 Jun 2010
TL;DR: The design process used for Foldit, a multiplayer online biochemistry game that presents players with computationally difficult protein folding problems in the form of puzzles, allowing ordinary players to gain expertise and help solve these problems, is discussed.
Abstract: Incorporating the individual and collective problem solving skills of non-experts into the scientific discovery process could potentially accelerate the advancement of science. This paper discusses the design process used for Foldit, a multiplayer online biochemistry game that presents players with computationally difficult protein folding problems in the form of puzzles, allowing ordinary players to gain expertise and help solve these problems. The principle challenge of designing such scientific discovery games is harnessing the enormous collective problem-solving potential of the game playing population, who have not been previously introduced to the specific problem, or, often, the entire scientific discipline. To address this challenge, we took an iterative approach to designing the game, incorporating feedback from players and biochemical experts alike. Feedback was gathered both before and after releasing the game, to create the rules, interactions, and visualizations in Foldit that maximize contributions from game players. We present several examples of how this approach guided the game's design, and allowed us to improve both the quality of the gameplay and the application of player problem-solving.

150 citations

Journal ArticleDOI
15 Apr 2016-Science
TL;DR: The results show that, remarkably, these grains lack carbon-bearing compounds and have been homogenized in the interstellar medium into silicates with iron inclusions, which suggest the presence of magnesium-rich grains of silicate and oxide composition, partly with Iron inclusions.
Abstract: Interstellar dust (ISD) is the condensed phase of the interstellar medium. In situ data from the Cosmic Dust Analyzer on board the Cassini spacecraft reveal that the Saturnian system is passed by ISD grains from our immediate interstellar neighborhood, the local interstellar cloud. We determine the mass distribution of 36 interstellar grains, their elemental composition, and a lower limit for the ISD flux at Saturn. Mass spectra and grain dynamics suggest the presence of magnesium-rich grains of silicate and oxide composition, partly with iron inclusions. Major rock-forming elements (magnesium, silicon, iron, and calcium) are present in cosmic abundances, with only small grain-to-grain variations, but sulfur and carbon are depleted. The ISD grains in the solar neighborhood appear to be homogenized, likely by repeated processing in the interstellar medium.

102 citations