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NASA NTRS1987

The solar system/interstellar medium connection - Gas phase abundances

Gas-phase abundances in the outer solar system are presented as diagnostics of the interstellar medium at the time of the solar system formation, some 4.55 billion years ago. Possible influences of the thermal and chemical histories of the primitive solar nebula and of the processes which led to the formation and evolution of the outer planets and comets on the elemental and molecular composition of the primordial matter are outlined. The major components of the atmospheres of the outer planets and of the comae of comets are identified, and the cosmogonical and cosmological implications are discussed.

Lutz, Barry L.↗

NASA NTRS1988

C/He abundances in WC stars

Recombination theory has been used to determine the C/He abundances in 17 southern WC stars from spectra in the H and K bands. An LTE treatment of C II provides C/He values in the 0.04-0.3 range, by number, and maximum allowance for possible non-LTE effects yields values in the 0.1-0.7 range, by number. C/He is shown to decrease from WC4 to WC7. The ionization balance is found to be lower than in previous reports. He(+)/He(2+) values are between 2.6 and 3.0 for WC5-8 stars, increasing to 7 for WC9 stars. Continuum slopes and corrections for the emission line contributions to the H and K magnitudes are evaluated.

Smith, Lindsey F.↗

NASA NTRS1988

The predicted abundances of deuterium-bearing gases in the atmospheres of Jupiter and Saturn

The first set of comprehensive thermochemical equilibrium and chemical kinetic calculations on the chemistry of deuterium-bearing gases in the deep atmospheres of Jupiter and Saturn is presented. The sensitivity of the results to variations in elemental and isotopic abundances is studied. Isotopic fractionation effects in the C-13/C12, N-15/N-14, and O-18/O-16 ratios in nonequilibrium species such as CO, CO2, HCN, and N2 are briefly considered.

Fegley, Bruce, Jr.↗

NASA NTRS1988

Primordial lithium - New reaction rates, new abundances, new constraints

Newly measured nuclear reaction rates for H-3(alpha, gamma)Li-7 (higher than previous values) and Li-7(p, alpha)He-4 (lower than previous values) are shown to increase the Li-7 yield from big band nucleosynthesis for lower baryon-to-photon ratio (less than about 4 x 10 to the 10th). Recent revisions in the He-3(alpha, gamma)Be-7 and the D(p, gamma)He-3 rates enhance the high (greater than 4 x 10 to the 10th) Li-7(Be) production. New, independent determinations of Li abundances in extreme population II stars are in excellent agreement with the work of Spites and give continued confidence in the use of Li-7 in big bang baryon density determinations.

Kawano, Lawrence↗

NASA NTRS1988

Iridium abundance maxima in the Upper Cenomanian extinction interval

Two iridium abundance peaks, both 0.11 ppb (whole-rock basis) over a local background of 0.017 ppb, have been found in Middle Cretaceous marine rocks near Pueblo, Colorado. They occur just below the 92-million-year-old Cenomanian-Turonian (C-T) stage boundary. No other peaks were found in 45 meters of strata (about 2.5 million years of deposition) above and below the boundary interval. The broad lower peak straddles the first in a series of extinctions of benthic and nektonic macrobiota which comprise the C-T extinction event. The sharp upper peak occurs stratigraphically about 1.2 meters above the lower peak. The excess Ir might be from meteoroid impacts.

Orth, C. J.↗

NASA NTRS1988

Carbon and helium abundances in Wolf-Rayet WC stars determined from optical recombination lines

Carbon to helium ratios and ionization fractions are derived for 74 WC stars in the Galaxy and the LMC from optically thin recombination lines at visual wavelengths. The range of C/He ratios is 0.13 to 0.79 by number, similar to the ratios calculated by Nugis (1975) and about 20 times greater than the ratios of Smith and Willis (1982). These ratios also agree with the abundances determined in the most recent evolutionary models of massive stars, which include mass loss, convective dredge-up, and new nuclear reaction rates. The range of values found for the C/He ratios implies that the convective cores of WC stars do not occupy a very large mass fraction. The C/He ratio differs within a subtype by a factor of three or less, but the mean tends to increase toward earlier subtypes, although the standard deviation from the mean is large enough to allow the interpretation that the C/He ratio is constant for all WC subtypes.

Torres, Ana V.↗

NASA NTRS1988

Temperature dependence of the abundances of elements in solar He-3 rich events

The element abundances in solar He-3-rich events are observed to vary with the soft X-ray temperature of the parent flare. The observations are consistent with thermal collisional ionization of the elements to the equilibrium-charge states expected within the flare-heated plasma at (10-15) x 10 to the 6th K. Proposed photoionization mechanisms appear to be excluded. Rapid ionization of the ions requires that the heating occur sufficiently low in the corona that the electron density exceed about (1-5) x 10 to the 8th/cu cm. Heavy-element enhancements might be a signature of material processed in the flash phase of events in contrast to unheated ambient material accelerated by a coronal shock.

Reames, D. V.↗

NASA NTRS1988

Infrared measurements of column abundances of several trace gases in the Antarctic atmosphere

Atmospheric emission measurements were made in 1978 from an LC 130 aircraft from Point Mugu, CA, to McMurdo Station, Antarctica, and from McMurdo over the Antarctic continent on several different flights. These included a number of flights over the South Pole. In December 1980, infrared solar spectra were obtained from the ground at South Pole Station. Infrared solar spectra were also obtained from South Pole during late November and early December of 1986. These latter measurements were extended to cover additional spectral regions to obtain column densities of a number of additional constituents. The results obtained from these measurement series are reviewed and, where measurements were made during both periods, compared. Spectral absorption or emission features due to HNO3, NO, NO2, HCl, (H-16)2O, (H-18)2O, HDO, CH4, and N2O were used to obtain data on the total column abundances for these compounds.

Murcray, F. J.↗

NASA NTRS1988

Measurements of the gas temperature and iron abundance distribution in the Coma Cluster

The medium energy X-ray detectors onboard the EXOSAT Observatory have been used to determine the gas temperature at several positions in the Coma Cluster of galaxies. Evidence is found at greater than 95 percent confidence for a higher temperature in the center of the cluster than in a position approximately 45 arcmin off-center. No difference in iron abundance is observed between the center and off-center regions and the equilibrium model for the distribution of elements in the Coma Cluster of Abramopoulos, Chanan, and Ku can be rejected with greater than 99.5 percent confidence, in favor of a model with more uniform composition. A phenomenological model is presented of the Coma Cluster, which is consistent with the data presented here, as well as the imaging data from the Einstein Observatory and the Tenma X-ray spectrum. The model has a central isothermal region of temperature about 9 keV extending to about 25 arcmin (about 1 Mpc). Beyond this radius the temperature falls as a polytrope with index about 1.6.

Hughes, John P.↗

NASA NTRS1988

Galactic interstellar abundance surveys with IUE. II - The equivalent widths and column densities

This paper continues a survey of interstellar densities, abundances, and cloud structure in the Galaxy, using the International Ultraviolet Explorer (IUE) satellite. Equivalent widths of 18 ultraviolet resonance transitions are presented and column densities for Si II, Mn II, Fe II, S II, and Zn II toward 261 early-type stars are derived. These equivalent widths and column densities agree within the stated errors of earlier Copernicus, BUSS, or IUE surveys of Mn II, Fe II, S II, and Zn II for 45 stars in common. The column densities are derived from single-component curves of growth with a common b-value based on that of Fe II and Si II.

Van Steenberg, Michael E.↗

NASA NTRS1988

Deuterium on Mars - The abundance of HDO and the value of D/H

Deuterium on Mars has been detected by the resolution of several Doppler-shifted lines of HDO near 3.7 micrometers in the planet's spectrum. The ratio of deuterium to hydrogen is (9 + or - 4) x 10 to the -4th; the abundance of H2O was derived from lines near 1.1 micrometers. This ratio is enriched on Mars over the telluric value by a factor of 6 + or - 3. The enrichment implies that hydrogen escaped more rapidly from Mars in the past than it does now, consistent with a dense and warm ancient atmosphere on the planet.

Owen, Tobias↗

NASA NTRS1988

Solar neon abundances from gamma-ray spectroscopy and He-3-rich particle events

Ambient solar atmospheric abundances derived from gamma-ray spectroscopy are compared with observations of solar energetic particles. Agreement is found between the gamma-ray-derived Ne/O ratio and the corresponding mean ratio for He-3-rich flares. Both of these values are significantly higher than inferred coronal Ne/O ratios. It is suggested that the mean Ne/O ratio in He-3-rich flares reflects the composition of the flare plasma rather than the acceleration process.

Reames, D. V.↗

NASA NTRS1988

The global distribution, abundance, and stability of SO2 on Io

Voyager multispectral mosaics, earth-observed spectra, and photometric characterizations have been used to model and globally map the SO2 distribution and abundances, the bolometric hemispheric albedos, and the passive surface temperatures on Io. The SO2 is noted to be concentrated in the bright equatorial band, while being deficient in the region defined by Pele-type volcanic eruptions and the polar regions. The brightest, locally coldest areas correspond to SO2-rich regions, although many small patches occur elsewhere. These results are found to support the regional cold-trapping model for the surface and atmospheric SO2 of Fanale et al. (1982).

Mcewen, Alfred S.↗

NASA NTRS1988

Carbon and nitrogen abundance determinations from transition layer lines

For red giants a smooth increase in the nitrogen to carbon abundance ratio for increasing B-V as is expected for the first dredge up phase when the outer convection zone deepens is found. An average increase in the nitrogen to silicon ratio for B-V = 0.6 which goes back to almost solar values for cool giants with B - V approximately 1.0 is reported. It looks as if Si would be enriched for deeper mixing contrary to expectations from standard evolution theory.

Boehm-Vitense, Erika↗

NASA NTRS1988

Cross Sections, relic abundance, and detection rates for neutralino dark matter

Neutralino annihilation and elastic scattering cross sections are derived which differ in important ways from previous work. These are applied to relic abundance calculations and to direct detection of neutralino dark matter from the galactic halo. Assuming the neutralino to be the lightest supersymmetric particle and that it is less massive than the Z sup 0, we find relic densities of neutralinos greater than 4 percent of critical density for almost all values of the supersymmetric parameters. We constrain the parameter space by using results from PETRA (chargino mass less than 23 GeV) and ASP, and then assuming a critical density of neutralinos, display event rates in a cryogenic detector for a variety of models. A new term implies spin independent elastic scattering even for those majorana particles and inclusion of propagator momenta increases detection rates by 10 to 300 percent for pure photinos. Z sup 0-squark interference leads to very low detection rates for some values of the parameters. The new term in the elastic cross section dominates for heavy, mostly spinless materials and mitigates the negative interference cancellations in light materials; except for the pure photino or pure higgsinos cases where it does not contribute. In general, the rates can be substantially different from the pure photino and pure higgsino special cases usually considered.

Griest, Kim↗

NASA NTRS1988

Observations of interstellar HOCO(+) - Abundance enhancements toward the Galactic center

The 4(04)-3(03) and 1(01)-0(00) transitions of HOCO(+) toward several molecular clouds have been monitored. Of the molecular clouds considered, the HOCO(+) molecule has been detected only in Sgr B2 and Sgr A. The results suggest that gas phase CO2 is not a major carbon reservoir in typical molecular clouds. For Sgr B2, the column density of HOCO(+) at the northern peak is found to be about 3 x 10 to the 14th/sq cm, and a fractional abundance relative to H2 is obtained which is about 2 orders of magnitude greater than recent theoretical predictions.

Minh, Y. C.↗

NASA NTRS1989

Isotope abundances of solar coronal material derived from solar energetic particle measurements

Coronal isotopic abundances for the elements He, C, N, O, Ne, and Mg are derived from previously published measurements of the isotopic composition of solar energetic particles by first measuring, and then correcting for, the charge-to-mass-dependent fractionation due to solar flare acceleration and propagation processes. The resulting coronal composition generally agrees with that of other samples of solar system material, but the previously noted difference between the solar flare and solar wind Ne-22/Ne-20 ratios remains unresolved.

Mewaldt, R. A.↗

NASA NTRS1989

The C-12/C-13 abundance ratio in Comet Halley

The individual (C-13)N rotational lines in Comet Halley are resolved using high-resolution spectra of the CN B2Sigma(+)-X2Sigma(+) (0,0) band. The observe C-12/C-13 abundance ratio excludes a site of origin for the comet near Uranus and Neptune and suggests a condensation environment quite distinct from other solar system bodies. Two theories are presented for the origin of Comet Halley. One theory suggest that the comet originated 4.5 Gyr ago in an inner Oort cloud at a heliocentric distance greater than 100 AU where chemical fractionation led to the C-13 enrichment in the CN parent molecule prior to condensation of the comet nucleus. According to the other, more plausible theory, the comet nucleus condensed relatively recently from the interstellar medium which has become enriches in C-13 and was subsequently gravitationally captured by the solar system.

Wyckoff, Susan↗