The Apollo SWC Experiment: Results, Conclusions, Consequences

Geiss, J.; Bühler, F.; Cerutti, H.; Eberhardt, P.; Filleux, C.; Meister, Jan B.; Signer, P.

doi:10.1023/b:spac.0000023409.54469.40

Cited by 76 publications

(117 citation statements)

References 59 publications

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“…The correlated variability indicates that the fractionation mechanism operates on both the elemental and the isotopic ratio simultaneously. Geiss et al 2004, and see Fig. 1).…”

Section: Introductionmentioning

confidence: 84%

“…Both the He/O-abundance ratio as well as the He/Ne-ratio have been determined in many instances, and one can safely give average ratios with uncertainties of the order of 20%. The most reliable value for the helium/neon ratio in the solar wind dates back to the work of Geiss et al (1972), who found (Geiss et al 1972). The correlated variability indicates that the fractionation mechanism operates on both the elemental and the isotopic ratio simultaneously.…”

Section: Introductionmentioning

confidence: 99%

“…The principal ingredients for this study are the helioseismologically determined solar helium abundance, the solar wind isotopic abundance ratios 3 He/ 4 He and 20 Ne/ 22 Ne, which have well been determined by means of the Apollo Foil experiments (cf. Geiss et al 2004), as well as the elemental abundance ratios He/Ne and Ne/O, which have been determined with the Apollo foils and the ISEE-3 Ion Composition Instrument (Kunz 1983;Bochsler et al 1986) and several other in-situ experiments, respectively. Hence, for our determination we use measurements, which do not depend on photospheric observations, nor on atomic properties, such as ft-values, nor on photospheric models.…”

Section: Introductionmentioning

confidence: 99%

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Solar abundances of oxygen and neon derived from solar wind observations

Bochsler¹

2007

A&A

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Context. Recently, a revision of the solar abundances of C, N, and O to substantially lower values has led to a controversy on solar opacities in the solar standard model and to the suggestion to revise the solar abundance of neon upward by as much as a factor of 1.6 leading to enhanced solar neon/oxygen abundance ratios by a factor of 3. Neon and oxygen are neighboring elements with easily defined charged states in the solar wind, and they have been well identified and measured for over two decades in the solar wind under many circumstances and with several instruments. The solar wind Ne/O ratio is 0.14 with a conservative error estimate of ±0.03, consistent with the coronal value derived from solar energetic particle measurements. Aims. We investigate, whether solar wind observations are consistent with the newly proposed elemental solar abundances of neon and oxygen. Methods. The solar helium abundance has been derived from helioseismological observations. Helium and neon abundances in the solar wind have been well determined with the Apollo Foil experiments and, more recently, confirmed with the Genesis sample return mission. With these observations and the neon/oxygen solar wind abundance ratio determined by in-situ mass-spectrometry and using a simple theoretical model of Coulomb-drag fractionation for the solar wind, we estimate solar abundances for neon and oxygen. Results. From the variability of the helium/oxygen and the helium/neon ratio in the solar wind and from theoretical considerations, we conclude that the helium/neon ratio in the outer solar convective zone is 900 ± 110. Our best estimates of the solar neon and oxygen abundances in logarithmic dex-units are [Ne] = 7.96 ± 0.13, and [O] = 8.87 ± 0.11. Conclusions. Our solar neon/oxygen abundance ratio is consistent with the ratio derived from EUV-spectra from SOHO/CDS. However, our absolute abundance for oxygen is only marginally compatible with the newly derived value for oxygen, and our neon value is clearly incompatible with the recently proposed enhancement of the solar neon abundance.

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“…The correlated variability indicates that the fractionation mechanism operates on both the elemental and the isotopic ratio simultaneously. Geiss et al 2004, and see Fig. 1).…”

Section: Introductionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Solar abundances of oxygen and neon derived from solar wind observations

Bochsler¹

2007

A&A

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“…The Apollo Solar Wind Composition (SWC) experiment was designed to measure the light solar wind noble gases on pristine metallic surfaces without such effects, and it was successfully carried out during Apollo 11-16, the first five lunar landing missions. In this experiment the Apollo crews exposed Al-and Pt-foils to the SW for up to 45 hours and the foils were returned to Earth where the directly implanted SW-He, Ne and Ar were analyzed in noble gas mass spectrometers (Geiss et al, , 2004. Since the exposure was short enough to avoid saturation effects, it was too short for analyses of the least abundant Xe and Kr and even the Ar analysis ( 36 Ar/ 38 Ar = 5.4 ± 0.3) was not sufficiently precise to delineate solar from terrestrial argon.…”

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confidence: 99%

Measuring the Isotopic Composition of Solar Wind Noble Gases

Meshik¹,

Hohenberg²,

Pravdivtseva³

et al. 2012

Exploring the Solar Wind

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“…The inspiration for Genesis was the Apollo Solar Wind Composition (SWC) foil experiments (18) which showed that the 20 Ne∕ 22 Ne ratio in the terrestrial atmosphere was 38% lower than that in the solar wind. Genesis has confirmed this important result with higher precision (6,19), and more importantly, extended the documentation of differences between the solar wind and terrestrial atmosphere to the other noble gases.…”

Section: Science Resultsmentioning

confidence: 99%

Solar composition from the Genesis Discovery Mission

Burnett

2011

Proc. Natl. Acad. Sci. U.S.A.

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Science results from the Genesis Mission illustrate the major advantages of sample return missions. (i) Important results not otherwise obtainable except by analysis in terrestrial laboratories: the isotopic compositions of O, N, and noble gases differ in the Sun from other inner solar system objects. The N isotopic composition is the same as that of Jupiter. Genesis has resolved discrepancies in the noble gas data from solar wind implanted in lunar soils.(ii) The most advanced analytical instruments have been applied to Genesis samples, including some developed specifically for the mission. (iii) The N isotope result has been replicated with four different instruments. T he Sun has obvious importance to the understanding of the physics of the solar system, but it is of equal major importance to the composition of planetary materials, i.e., the research area known as cosmochemistry. The link between solar and planetary matter is that they have a common origin in the original cloud of gas and dust from which the solar system formed 4.57 × 10 9 years ago. Our gas-dust cloud is the first step in what cosmochemists regard, at least implicitly, as a "Standard Model" for the origin of planetary materials. The formation of the Sun by gravitational collapse of the cloud occurs by the flow of material through an equatorial disk, the "solar nebula," onto the Sun, a process now directly observable in star-forming regions. The Standard Model regards elemental (the relative amounts of different elements) and isotopic (the relative amounts of the isotopes of individual elements) compositions of the solar nebula as homogeneous, at least on large scales relative to the size of individual dust grains. The planetary objects (planets, moons, asteroids, etc

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The Apollo SWC Experiment: Results, Conclusions, Consequences

Cited by 76 publications

References 59 publications

Solar abundances of oxygen and neon derived from solar wind observations

Solar abundances of oxygen and neon derived from solar wind observations

Measuring the Isotopic Composition of Solar Wind Noble Gases

Solar composition from the Genesis Discovery Mission

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