+ Visit NASA.gov + Contact NASA   + Home Select Search Field * All Report - Patent Number Abstract *Accession Number *NASA Center *Author NameDocument IDKeywordsPublication Date *Title * Find Results With All of the words At least one of the words Enter Search Term  within returned results    Search Tips: Use only the fields with * to search NIX collection. Enclose terms in double quotation marks (") to search for exact phrases, ie: "space shuttle". NOTE: Commas and dashes are removed from search term by search engine. Select Reset Search button to start a new search. See Help for more tips. + Publication Year + Subject + Availability Options + Item/Media Type Selected Navigations: Author > Dehart, John M. [x] Sort results by: NASA Center | Date Added to NTRS | Publication Year There are a total of 8 record(s) matching your query. Sorted by: Date Added To NTRS in Descending order On the origin of enstatite chondrite chondrules based on their petrography and comparison with experimentally produced chondrules Author(s): Lofgren, Gary E.; Dehart, John M.; Burkett, P. J. Abstract: The recent discovery of several types 3 and 4 enstatite chondrites (EC) in the Antarctic collection increases greatly the ability to compare unaltered, naturally-formed EC chondrules with chondrules produced experimentally ... NASA Center: Johnson Space Center Publication Year: 1994 Added to NTRS: 2008-06-02 Accession Number: 94N36158; Document ID: 19940031651 The occurrence of blue luminescing enstatite in E3 and E4 chondrites Author(s): Dehart, John M.; Lofgren, Gary E. Abstract: Two compositional types of enstatite that emit cathodoluminescence (CL) are known to exist in E3 and E4 chondrites. The first type consists of the most common enstatites that are relatively FeO-poor and emit a red CL. Their ... NASA Center: Johnson Space Center Publication Year: 1994 Added to NTRS: 2008-06-02 Accession Number: 94N35423; Document ID: 19940030917 Experimentally reproduced relict enstatite in porphyritic chondrules of enstatite chondrite composition Author(s): Lofgren, Gary E.; Dehart, John M.; Dickinson, Tammy L. Abstract: Experiments are presented that test a model for the origin of porphyritic pyroxene (PP) chondrules in enstatite chondrites that contain phenocrysts of enstatite with blue cathodoluminescence (CL) set in a matrix of radial, ... NASA Center: Johnson Space Center Publication Year: 1993 Added to NTRS: 2008-06-02 Accession Number: 94N16363; Document ID: 19940011890 Dynamic crystallization characteristics of enstatite chondrite chondrules Author(s): Lofgren, Gary E.; Dehart, John M.; Lanier, A. B. Abstract: Although the chemical properties of enstatite and ordinary chondrites are distinctly different, they both contain chondrules with a similar array of textures. This similarity suggests like origins. Textural studies using ... NASA Center: Johnson Space Center Publication Year: 1991 Added to NTRS: 2008-05-31 Accession Number: 92N12923; Document ID: 19920003705 Low temperature annealing and cathodoluminescence studies of type 1 chondrule compositions Author(s): Dehart, John M.; Lofgren, Gary E. Abstract: Preliminary results indicate that the yellow luminescing mesostases in type I chondrules can be altered by the effects of the low level thermal metamorphism. Although heat alone was insufficient to alter the CL, reheating ... NASA Center: Johnson Space Center Publication Year: 1991 Added to NTRS: 2008-05-31 Accession Number: 92N12913; Document ID: 19920003695 A compositional classification scheme for meteoritic chondrules Author(s): Sears, Derek W. G.; Jie, LU; Benoit, Paul H.; Dehart, John M.; Lofgren, Gary E. Abstract: A compositionally based classification scheme for chondrules is proposed that will help in systematizing the wealth of data available and disentangling the effects of nebular and subsequent processes. The classification is ... NASA Center: Johnson Space Center Publication Year: 1992 Added to NTRS: 2004-11-03 Accession Number: 92A40557; Document ID: 19920057933 Chemical and physical studies of chondrites. X - Cathodoluminescence and phase composition studies of metamorphism and nebular processes in chondrules of type 3 ordinary chondrites Author(s): Dehart, John M.; Lofgren, Gary E.; Jie, LU; Benoit, Paul H.; Sears, Derek W. G. Abstract: The cathodoluminescence (CL) characteristics of eight type-3 ordinary chondrites and one L5 chondrite were investigated with particular emphasis on detailed compositions of the relevant phases in four of these chondrites: ... NASA Center: Johnson Space Center Publication Year: 1992 Added to NTRS: 2004-11-03 Accession Number: 93A12353; Document ID: 19930028356 Cathodoluminescence properties of components in enstatite chondrites Author(s): Dehart, John M.; Lofgren, Gary E. Abstract: As a group, the enstatite chondrites are notable by the extremely low FeO content of most of their silicates. This property predisposes many of these materials to emit Cathodoluminescence (CL). Since examination of the CL ... NASA Center: Johnson Space Center Publication Year: 1993 Added to NTRS: 2004-11-03 Accession Number: 94N12206; Document ID: 19940007734 + Back to Top + Sponsored by the NASA Scientific and Technical    Information Program + 2004 Vision for Space Exploration + Freedom of Information Act + NASA Web Privacy Policy and Important Notices + NASA Disclaimers, Copyright Notice,    and Terms and Conditions of Use NASA Official: Calvin Mackey Page Curator: NASA Center for AeroSpace Information (help@sti.nasa.gov) Last Updated: July 5, 2007