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Reedy RC, Arnold JR, Trombka JI. Expected γ ray emission spectra from the lunar surface as a function of chemical composition. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/jb078i026p05847] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Boynton WV, Taylor GJ, Evans LG, Reedy RC, Starr R, Janes DM, Kerry KE, Drake DM, Kim KJ, Williams RMS, Crombie MK, Dohm JM, Baker V, Metzger AE, Karunatillake S, Keller JM, Newsom HE, Arnold JR, Brückner J, Englert PAJ, Gasnault O, Sprague AL, Mitrofanov I, Squyres SW, Trombka JI, d'Uston L, Wänke H, Hamara DK. Concentration of H, Si, Cl, K, Fe, and Th in the low- and mid-latitude regions of Mars. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2007je002887] [Citation(s) in RCA: 234] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Boynton WV, Feldman WC, Squyres SW, Prettyman TH, Bruckner J, Evans LG, Reedy RC, Starr R, Arnold JR, Drake DM, Englert PAJ, Metzger AE, Mitrofanov I, Trombka JI, D'Uston C, Wanke H, Gasnault O, Hamara DK, Janes DM, Marcialis RL, Maurice S, Mikheeva I, Taylor GJ, Tokar R, Shinohara C. Distribution of hydrogen in the near surface of Mars: evidence for subsurface ice deposits. Science 2002; 297:81-5. [PMID: 12040090 DOI: 10.1126/science.1073722] [Citation(s) in RCA: 753] [Impact Index Per Article: 34.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Using the Gamma-Ray Spectrometer on the Mars Odyssey, we have identified two regions near the poles that are enriched in hydrogen. The data indicate the presence of a subsurface layer enriched in hydrogen overlain by a hydrogen-poor layer. The thickness of the upper layer decreases with decreasing distance to the pole, ranging from a column density of about 150 grams per square centimeter at -42 degrees latitude to about 40 grams per square centimeter at -77 degrees. The hydrogen-rich regions correlate with regions of predicted ice stability. We suggest that the host of the hydrogen in the subsurface layer is ice, which constitutes 35 +/- 15% of the layer by weight.
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Affiliation(s)
- W V Boynton
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA.
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Trombka JI, Squyres SW, Bruckner J, Boynton WV, Reedy RC, McCoy TJ, Gorenstein P, Evans LG, Arnold JR, Starr RD, Nittler LR, Murphy ME, Mikheeva I, McNutt RL, McClanahan TP, McCartney E, Goldsten JO, Gold RE, Floyd SR, Clark PE, Burbine TH, Bhangoo JS, Bailey SH, Petaev M. The elemental composition of asteroid 433 eros: results of the NEAR-shoemaker X-ray spectrometer. Science 2000; 289:2101-5. [PMID: 11000107 DOI: 10.1126/science.289.5487.2101] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
We report major element composition ratios for regions of the asteroid 433 Eros imaged during two solar flares and quiet sun conditions during the period of May to July 2000. Low aluminum abundances for all regions argue against global differentiation of Eros. Magnesium/silicon, aluminum/silicon, calcium/silicon, and iron/silicon ratios are best interpreted as a relatively primitive, chondritic composition. Marked depletions in sulfur and possible aluminum and calcium depletions, relative to ordinary chondrites, may represent signatures of limited partial melting or impact volatilization.
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Affiliation(s)
- JI Trombka
- Goddard Space Flight Center, Code 691, Greenbelt, MD 20771, USA. Space Sciences Building, Cornell University, Ithaca, NY 14853, USA. Max-Planck-Institut fur Chemie, Postfach 3060, D-55020 Mainz, Germany. Department of Planetary Science, Spac
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Trombka JI, Floyd SR, Boynton WV, Bailey S, Brückner J, Squyres SW, Evans LG, Clark PE, Starr R, Fiore E, Gold R, Goldsten J, McNutt R. Compositional mapping with the NEAR X ray/gamma ray spectrometer. ACTA ACUST UNITED AC 1997. [DOI: 10.1029/97je00270] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Clark PE, Trombka JI. Remote X-ray spectrometry for NEAR and future missions: Modeling and analyzing X-ray production from source to surface. ACTA ACUST UNITED AC 1997. [DOI: 10.1029/97je01086] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Boynton WV, D'Uston LC, Young DT, Lunine JI, Waite JH, Bailey SH, Berthelier JJ, Bertaux JL, Borrel V, Burke MF, Cohen BA, McComas DH, Nordholt JE, Evans LG, Trombka JI. The determination of ice composition with instruments on cometary landers. Acta Astronaut 1997; 40:663-674. [PMID: 11540784 DOI: 10.1016/s0094-5765(97)00005-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The determination of the composition of materials that make up comets is essential in trying to understand the origin of these primitive objects. The ices especially could be made in several different astrophysical settings including the solar nebula, protosatellite nebulae of the giant planets, and giant molecular clouds that predate the formation of the solar system. Each of these environments makes different ices with different composition. In order to understand the origin of comets, one needs to determine the composition of each of the ice phases. For example, it is of interest to know that comets contain carbon monoxide, CO, but it is much more important to know how much of it is a pure solid phase, is trapped in clathrate hydrates, or is adsorbed on amorphous water ice. In addition, knowledge of the isotopic composition of the constituents will help determine the process that formed the compounds. Finally, it is important to understand the bulk elemental composition of the nucleus. When these data are compared with solar abundances, they put strong constraints on the macro-scale processes that formed the comet. A differential scanning calorimeter (DSC) and an evolved gas analyzer (EGA) will make the necessary association between molecular constituents and their host phases. This combination of instruments takes a small (tens of mg) sample of the comet and slowly heats it in a sealed oven. As the temperature is raised, the DSC precisely measures the heat required, and delivers the gases to the EGA. Changes in the heat required to raise the temperature at a controlled rate are used to identify phase transitions, e.g., crystallization of amorphous ice or melting of hexagonal ice, and the EGA correlates the gases released with the phase transition. The EGA consists of two mass spectrometers run in tandem. The first mass spectrometer is a magnetic-sector ion-momentum analyzer (MAG), and the second is an electrostatic time-of-flight analyzer (TOF). The TOF acts as a detector for the MAG and serves to resolve ambiguities between fragments of similar mass such as CO and N2. Because most of the compounds of interest for the volatile ices are simple, a gas chromatograph is not needed and thus more integration time is available to determine isotopic ratios. A gamma-ray spectrometer (GRS) will determine the elemental abundances of the bulk cometary material by determining the flux of gamma rays produced from the interaction of the cometary material with cosmic ray produced neutrons. Because the gamma rays can penetrate a distance of several tens of centimeters a large volume of material is analyzed. The measured composition is, therefore, much more likely to be representative of the bulk comet than a very small sample that might have lost some of its volatiles. Making these measurements on a lander offers substantial advantages over trying to address similar objectives from an orbiter. For example, an orbiter instrument can determine the presence and isotopic composition of CO in the cometary coma, but only a lander can determine the phase(s) in which the CO is located and separately determine the isotopic composition of each reservoir of CO. The bulk composition of the nucleus might be constrained from separate orbiter analyses of dust and gas in the coma, but the result will be very model dependent, as the ratio of gas to dust in the comet will vary and will not necessarily be equal to the bulk value.
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Boynton WV, Trombka JI, Feldman WC, Arnold JR, Englert PAJ, Metzger AE, Reedy RC, Squyres SW, Wänke H, Bailey SH, Brückner J, Callas JL, Drake DM, Duke P, Evans LG, Haines EL, McCloskey FC, Mills H, Shinohara C, Starr R. Science applications of the Mars Observer gamma ray spectrometer. ACTA ACUST UNITED AC 1992. [DOI: 10.1029/92je00538] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Lang FL, Werntz CW, Crannell CJ, Trombka JI, Chang CC. Cross sections for production of the 15.10-MeV and other astrophysically significant gamma-ray lines through excitation and spallation of 12C and 16O with protons. Phys Rev C Nucl Phys 1987; 35:1214-1227. [PMID: 9953888 DOI: 10.1103/physrevc.35.1214] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Yin LI, Trombka JI, Seltzer SM, Bielefeld MJ. X-ray imaging of extended objects using nonoverlapping redundant array. Appl Opt 1983; 22:2155. [PMID: 18196099 DOI: 10.1364/ao.22.002155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
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Abstract
A simple device is described that is capable of providing real-time 3-D viewing of extended x-ray and gamma-ray objects. The visible-light images produced by the device are not merely stereoscopic, i.e., one perspective, but possess both horizontal and vertical parallax with a reasonably large field of view.
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Metzger AE, Trombka JI, Peterson LE, Reedy RC, Arnold JR. Lunar Surface Radioactivity: Preliminary Results of the Apollo 15 and Apollo 16 Gamma-Ray Spectrometer Experiments. Science 1973; 179:800-3. [PMID: 17806299 DOI: 10.1126/science.179.4075.800] [Citation(s) in RCA: 84] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Gamma-ray spectrometers on the Apollo 15 and Apollo 16 missions have been used to map the moon's radioactivity over 20 percent of its surface. The highest levels of natural radioactivity are found in Mare Imbrium and Oceanus Procellarum with contrastingly lower enhancements in the eastern maria. The ratio of potassium to uranium is higher on the far side than on the near side, although it is everywhere lower than commonly found on the earth.
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Abstract
Changes in the slope of a measured distribution may be explained partially by the effect of the measurement process itself.
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Affiliation(s)
- J I Trombka
- Goddard Space Flight Center, Greenbelt, Maryland, USA
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