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NASA NTRS2006

Cross Sections for Electron Impact Excitation of Astrophysically Abundant Atoms and Ions

Electron collisional excitation rates and transition probabilities are important for computing electron temperatures and densities, ionization equilibria, and for deriving elemental abundances from emission lines formed in the collisional and photoionized astrophysical plasmas. Accurate representation of target wave functions that properly account for the important correlation and relaxation effects and inclusion of coupling effects including coupling to the continuum are essential components of a reliable collision calculation. Non-orthogonal orbitals technique in multiconfiguration Hartree-Fock approach is used to calculate oscillator strengths and transition probabilities. The effect of coupling to the continuum spectrum is included through the use of pseudostates which are chosen to account for most of the dipole polarizabilities of target states. The B-spline basis is used in the R-matrix approach to calculate electron excitation collision strengths and rates. Results for oscillator strengths and electron excitation collision strengths for transitions in N I, O I, O II, O IV, S X and Fe XIV have been produced

Tayal, S. S.↗
NASA NTRS1984

Is phosphorus predictably incompatible in igneous processes?

Siderophile element abundances are central to recent models for core formation in the Earth and Moon and the origin of the Moon. It is important to identify siderophile elements whose behavior in igneous processes is predictable, so that primary mantle abundances can be deduced by subtracting out the effects of igneous processes. Newsom's model for core formation in the Moon requires subchondritic P, and suggests that P was depleted due to volatility. Experiments were conducted to determine P olivine/liquid distribution coefficients. Preliminary results indicate that P can be compatible with olivine during rapid cooling, but is not during isothermal crystallization with long growth times, and tends to be expelled during annealing. It is therefore not likely that P is compatible under any widespread igneous conditions, and the incompatible behavior of P in lunar crustal rocks can be safety assumed. In addition, low fO2 is insufficient to cause P compatibility, so it is unlikely that P-rich silicates formed during the early evolution of the Earth or Moon. These results indicate that P is depleted in the Moon.

Goodrich, C. A.↗
NASA NTRS1983

The isotropic condition of energetic particles emitted from a large solar flare

Isotope abundance ratios for 5 to 50 MeV/nuc nuclei from a large solar flare were measured. The measurements were made by the heavy isotope spectrometer telescope (HIST) on the ISEE-3 satellite orbiting the Sun near an Earth-Sun liberation point approximately one million miles sunward of the Earth. Finite values for the isotope abundance ratios C-13/C-12, N-15/N-14, O-18/O-16, Ne-22/Ne-20, Mg-25/Mg-24, and Mg-26/Mg-24, and upper limits for the isotope abundance ratios He-3/He-4, C-14/C-12, O-17/O-16 and Ne-21/Ne-20 were reported. Element abundances and spectra were measured to compare the flare with other reported flares. The flare is a typical large flare with low Fe/O abundance or = to 0.1). For C-13/C-12, N-15/N-14, O-18/O-16, Mg-25/Mg-24 and Mg-26/Mg-24 isotope abundance ratios agree with the solar system abundance ratios. Measurement for Ne-22/Ne-20 agree with the isotopic composition of the meteoritic component neon-A.

Spalding, J.↗
NASA NTRS1991

Lunar ferroan anorthosites and mare basalt sources - The mixed connection

Global overturn of a hot, gravitationally unstable lunar mantle immediately following the solidification of a magma ocean explains several characteristics of lunar petrology. Lunar mare basalt sources are inferred to be depleted in europium and alumina. These depletions are consensually attributed to complementary plagioclase floating from a magma ocean. However, in contrast to the mare basalt source parent magma, the ferroan anorthosite parent magma was more evolved by virtue of its lower Mg/Fe ratio and Ni abundances, although less evolved in its poverty of clinopyroxene constituents, flat rare earth pattern, and lower incompatible element abundances. The europium anomaly in mare sources is inferred to be present at 400 km depth, too deep to have been directly influenced by plagioclase crystallization. Massive overturning of the post-magma ocean mantle would have carried down clinopyroxene, ilmenite, and phases containing fractionated rare earths, europium anomalies, and some heat-producing radionuclides.

Ryder, Graham↗
NASA NTRS2000

First Light Measurements with the XMM-Newton Reflection Grating Spectrometers: Evidence for an Inverse First Ionization Potential Effect and Anomalous Ne Abundance in the Coronae of HR 1099

The RS CVn binary system HR 1099 was extensively observed by the XMM-Newton observatory in February 2000 as its first-light target. A total of 570 ks of exposure time was accumulated with the Reflection Grating Spectrometers (RGS). The integrated X-ray spectrum between 5-38A is of unprecedented quality and shows numerous features attributed to transitions of the elements C, N, O, Ne, Mg, Si, S, Fe. Ni, and probably others. We perform an in-depth study of the elemental composition of the average corona of this system, and find that the elemental abundances strongly depend on the first ionisation potential (FIP) of the elements. But different from the solar coronal case, we find an inverse FIP effect, i.e., the abundances (relative to oxygen) increase with increasing FIP. Possible scenarios, e.g., selective enrichment due to Ne-rich flare-like events, are discussed.

Brinkman, A. C.↗
NASA NTRS1994

Chemical models of the deep atmospheres of Jupiter and Saturn

New and updated chemical kinetic data, elemental abundances, and thermodynamic data are used for thermochemical equilibrium and, where relevant, thermochemical kinetic calculations of gas abundances and condensate stability in the hot, deep atmospheres of Jupiter and Saturn. Over 2000 compounds of all naturally occurring elements in the periodic table are considered. The calculations range from 298 to 2000 K and are done for adiabatic models of the two planetary atmospheres. The results predict the abundances of many gases which are potentially observable by the Galileo probe to Jupiter, by the Cassini mission to Saturn, and by Earth-based and Earth-orbital telescopes. In addition, the results also predict many new species which are potentially observable by a new generation of entry probes capable of penetrating deeper into the atmospheres of Jupiter and Saturn.

Fegley, Bruce, Jr.↗
NASA NTRS1979

On the ionization equilibrium balance

Ionization equilibrium for the most astrophysically abundant elements are calculated using multilevel atomic models for several stages of ionization. It is found that the relative abundance of the lithium-, beryllium-, and boron-like ions at electron densities as low as 1 million per cu cm is density-dependent. Because of this dependence, the intensity of lines arising from ions of the Li, Be, and B isoelectronic sequences are density-sensitive. The general implications of these results as applied to solar and stellar atmospheric models, coronal abundances, and spectroscopic diagnostic techniques are discussed.

Vernazza, J. E.↗
NASA NTRS1992

Heliosphere Instrument for Spectra, Composition and Anisotropy at Low Energies

The Heliosphere Instrument for Spectra, Composition, and Anisotropy at Low Energies (HI-SCALE) is designed to make measurements of interplanetary ions and electrons throughout the entire Ulysses mission. The ions (E(i) greater than about 50 keV) and electrons (E(e) greater than about 30 keV) are identified uniquely and detected by five separate solid-state detector telescopes that are oriented to give nearly complete pitch-angle coverage from the spinning spacecraft. Ion elemental abundances are determined by Delta E vs E telescope using a thin (5 microns) front solid state detector element in a three-element telescope. Experimental operation is controlled by a microprocessor-based data system. Inflight calibration is provided by radioactive sources mounted on telescope covers which can be closed for calibration purposes and for radiation protection during the course of the mission. Ion and electron spectral information is determined using both broad-energy-range rate channels and a 32 channel pulse-height analyzer for more detailed spectra. Some initial in-ecliptic measurements are presented which demonstrate the features of the instrument.

Lanzerotti, L. J.↗
NASA NTRS2010

High Pressure/Temperature Metal Silicate Partitioning of Tungsten

The behavior of chemical elements during metal/silicate segregation and their resulting distribution in Earth's mantle and core provide insight into core formation processes. Experimental determination of partition coefficients allows calculations of element distributions that can be compared to accepted values of element abundances in the silicate (mantle) and metallic (core) portions of the Earth. Tungsten (W) is a moderately siderophile element and thus preferentially partitions into metal versus silicate under many planetary conditions. The partitioning behavior has been shown to vary with temperature, silicate composition, oxygen fugacity, and pressure. Most of the previous work on W partitioning has been conducted at 1-bar conditions or at relatively low pressures, i.e. <10 GPa, and in two cases at or near 20 GPa. According to those data, the stronger influences on the distribution coefficient of W are temperature, composition, and oxygen fugacity with a relatively slight influence in pressure. Predictions based on extrapolation of existing data and parameterizations suggest an increased pressured dependence on metal/ silicate partitioning of W at higher pressures 5. However, the dependence on pressure is not as well constrained as T, fO2, and silicate composition. This poses a problem because proposed equilibration pressures for core formation range from 27 to 50 GPa, falling well outside the experimental range, therefore requiring exptrapolation of a parametereized model. Higher pressure data are needed to improve our understanding of W partitioning at these more extreme conditions.

Shofner, G. A.↗
NASA NTRSDate not supplied

On the Hunt for Detectable Biosignatures in Jezero Crater: What to Look for and Where

Introduction: The Perseverance rover, which is currently exploring Jezero crater on Mars, is equipped with seven instruments that allow for observation of textures, minerals, color, structure, and chemistry of rocks and sediments in order to search for signs of ancient life, understand the geologic history of the crater, and identify candidates for sample return (Farley et al. 2020). The first of these aims includes the direct detection of potential biosignatures, including textures, organic molecules, minerals, and elemental chemistries that are of biogenic origin (Mustard et al. 2013). The presence of these biosignatures will be constrained by the habitability of the local region, the preservation potential of the host rocks, and the sensitivity of the instrument suite, and their biogenicity will be investigated after return to Earth as part of the Mars Sample Return campaign. Here, we examine key targets on the three planned campaigns, potential biosignatures that may be present, and the capabilities of key rover instruments. High Potential Biosignature Sites in Jezero: To date, measurements have been made on multiple sites that both contain minerals known in terrestrial settings to preserve biosignatures and likely were habitable settings (Williford et al. 2021). Two examples include the fine-grained rocks at the base of the delta fan and the NW inner margin of the crater. Fine-grained Rocks at Base of Delta Fan. Fine-grained, clay-bearing rocks may have been deposited as muddy lake sediments that could have hosted life and preserved biosignatures settling out of the water column. The report of organic molecules by the Curiosity rover in the Sheepbed mudstone and Murray formation has highlighted this site in particular. Potential biosignatures in mudstones, especially those rich in silica (McMahon et al. 2018), microbialites and complex organics. NW Inner Margin of Crater. This unit, located along the inner margin of the crater, contains strong carbonate signatures and may have been the littoral zone of a lake (Horgan et al. 2020). The potential biosignatures here include microfossils, microbialites, biominerals, and complex organics. Detectability of Biosignatures by the Mars 2020 Instrument Suite: The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument comprises a Deep UV spectrometer, context imager, and color camera to generate spatially resolved chemical maps (Bhartia et al. 2020). It is sensitive to trace organics as well as a range of minerals and can detect native fluorescence from aromatic organics; the WATSON and ACI cameras can be used to observe morphologies such as stromatolitic laminations or filaments ranging from the tens of micron to millimeter scale. SHERLOC can detect organics that may be present in either of the high potential biosignature targets, as well as detect carbonates in the latter. However, the presence of high amounts of iron, such as in iron-rich clays, would cause attenuation of spectral response through UV absorption. The Planetary Instrument for X-ray Lithochemistry (PIXL) comprises an X-ray fluorescence spectrometer and camera that can scan rock surfaces to generate elemental maps (Allwood et al. 2020). PIXL can detect chemical biosignatures such as spatial variations of elemental abundances that may have resulted from biological activity. PIXL would be particularly useful in detecting fine textures and elemental chemistries in either high potential biosignature target, but cannot directly detect minerals such as carbonate. The SuperCam instrument performs three types of spectroscopy, color imaging, and acoustic recording to remotely examine elemental composition, minerals, organics, and textures (Maurice et al. 2021). Using laser induced breakdown spectroscopy and time resolved luminescence spectroscopy, SuperCam can detect major elemental building blocks of organics (i.e., C, H, N, O, P, S) and conjugated organic structures, respectively, which may be found in either site. While in other contexts, luminescence is a useful tool for biosignature identification, luminescence generated by the 532 nm laser may obscure the Raman signal. Conclusion: The three instruments discussed can be used collaboratively to establish the presence of potential biosignatures in samples. These high-priority samples may then be returned to Earth for detailed laboratory analysis.

S. Sharma↗
NASA NTRS1990

Solar accelerated particles - Comparisons of abundances and energy spectra from particle and gamma-ray observations

Gamma-ray observations of the April 27, 1981 flare have been used to derive elemental abundances of both the ambient gas and the accelerated particle which interact with this gas to produce gamma rays. The results show that the abundances of the accelerated particles which produce the gamma rays are much more consistent with first-class particle abundances than with large proton-flare abundances. Observed bremsstrahlung spectral from 16 flares are compared with calculated bremsstrahlung spectra. It is concluded that the electrons observed in interplanetary space and the electrons responsible for gamma-ray production cannot be drawn from the same accelerated particle population without the former being affected by reacceleration or energy-dependent escape.

Ramaty, R.↗
NASA NTRS1989

Abundances of ultraheavy elements in the cosmic radiation - Results from HEAO 3

An analysis is presented that, for the first time, systematically normalizes the data from the HEAO 3 heavy nuclei experiment on the cosmic-ray abundances of all the elements heavier than germanium to that of iron. In the range of atomic number Z from 33 to 60, the analysis yields abundances of odd-even element pairs. The abundances are consistent with a cosmic-ray source having a composition similar to that of the solar system, but subject to source fractionation correlated with the first ionization potential (FIP) of each element. For Z greater than 60, the analysis yields abundances of element groups. For these heaviest nuclei, we find an enhancement of the abundance of the platinum group, elements with Z of 74-80, relative to that in propagated solar system source, and a corresponding increase in the abundance of the largely secondary elements in the 62-73 range. These abundances suggest that there is an enhancement of the r-process contribution to the source nuclei in the Z greater than 60 charge region. Over the entire region of charge, standard leaky box models of propagation satisfactorily model secondary production.

Binns, W. R.↗
NASA NTRS1974

Absolute spectrophotometry in M31 and M32

For a number of places in the bulge of M31 and for two places in M32 photometric scans from 3300 A to 10,600 A have been obtained with the multichannel spectrometer on the 5-meter Hale telescope. The scans show that in both objects the color temperature (particularly shortwards of 5000 A) decreases towards the center and that the strength of the CN bands increases towards the center in both objects in agreement with earlier observations. The new data can all be interpreted in terms of an increase of heavy element abundance towards the center in both objects by a factor probably less than 2 and by an excess of heavy elements in M31 compared to M32 by a factor probably greater than 2, in qualitative agreement with earlier conclusions.

Oke, J. B.↗
NASA NTRS1975

Absolute spectrophotometry in M31 and M32

For a number of places in the bulge of M31, and for two places in M32, photometric scans from lambda = 3300 A to lambda = 10,600 A have been obtained with the multichannel spectrometer on the 5-m Hale telescope. The scans show that in both objects the color temperature (particularly shortward of 5000 A) decreases toward the center, and that the strength of the CN bands increases toward the center in both objects, in agreement with other earlier observations. The new data can all be interpreted in terms of an increase of heavy-element abundance toward the center in both objects by a factor probably less than 2, and by an excess of heavy elements in M31 compared with M32 by a factor probably greater than 2, in qualitative agreement with earlier conclusions of other observers.

Oke, J. B.↗
NASA NTRS1984

Abundances in galactic H2 regions, 3: G25.4-0.2, G45.5+0.06, M8, S159 and DR22

Measurements of the ARII (6.99 microns), ArIII (8.99 microns), NeII (12.81 microns), SIII (18.71 microns), and SIV (10.51 microns) lines are presented for five compact HII regions along with continuum spectroscopy. From these data and radio data, lower limits to the elemental abundances of Ar, S, and Ne were deduced. The complex G25.4-0.2 is only 5.5 kpc from the galactic center, and is considerably overabundant in all these elements. Complex G45.5+0.06 is at seven kpc from the galactic center, and appears to be approximately consistent with solar abundance. The complex S159 in the Perseus Arm, at 12 kpc from the galactic center, has solar abundance, while M8 in the solar neighborhood may be somewhat overabundant in Ar and Ne. Complex DR 22, at 10 kpc from the galactic center in the Cygnus Arm, is overabundant in Ar. A summary of results from a series of papers on abundances is given.

Pipher, J. L.↗
NASA NTRS1984

Abundances in galactic H II regions. III - G25.4-0.2, G45.5+0.06, M8, S159, and DR 22

Measurements of the ARII (6.99 microns), ArIII (8.99 microns), NeI (12.81 microns), SIII (18.71 microns), and SIV (10.51 microns) lines are presented for five compact HII regions along with continuum spectroscopy. From these data and radio data, lower limits to the elemental abundances of Ar, S, and Ne were deduced. The complex G25.4-0.2 is only 5.5 kpc from the galactic center, and is considerably overabundant in all these elements. Complex G45.5+0.06 is at seven kpc from the galactic center, and appears to be approximately consistent with solar abundance. The complex S159 in the Perseus Arm, at 12 kpc from the galactic center, has solar abundance, while M8 in the solar neighborhood may be somewhat overabundant in Ar and Ne. Complex DR 22, at 10 kpc from the galactic center in the Cygnus Arm, is overabundant in Ar. A summary of results from a series of papers on abundances is given.

Pipher, J. L.↗
NASA NTRS1982

The ultraviolet spectrum of the Crab Nebula

Ultraviolet spectroscopy of the Crab Nebula done by the International Ultraviolet Explorer satellite is described, and an estimate of the carbon abundance is made, noting data reduction to remove spectral defects caused by radiation hits. The important C IV 1549, He II 1640, and semiforbidden C III 1908 emission line intensities were measured and upper limits placed on other ultraviolet features for the brightest filamentary region in the Nebula. The emission lines imply an average ionic abundance ratio n(C+2)/n(O+2) in the range from 0.4 to 1.5 in the observed gaseous condensations. The elemental abundance ratio of carbon to oxygen is probably in the same range. Analysis shows that there is no perceptible excess of carbon due to presupernova nucleosynthesis in the observed region. The large helium abundance, small carbon and oxygen abundances, and presence of a neutron star in the Crab Nebula suggest that the presupernova star had a mass close to eight solar masses.

Davidson, K.↗
NASA NTRS1983

Origin of Archean anorthosites - Evidence from the Bad Vermilion Lake anorthosite complex, Ontario

Studies of the petrology and geochemistry of the anorthosite complex at Bad Vermillion Lake, Canada, based on 400 samples collected in summer, 1979, are presented. Petrographic, microprobe, X-ray-fluorescence, and instrumental-neutron-activation analyses were performed. Major and trace-element abundances of the anorthositic rocks and surrounding mafic and felsic rocks are reported in tables, chondrite-normalized rare-earth-element patterns are shown, and the anorthositic, intrusive, and metavolcanic formations are characterized in detail. The anothrositic plagioclases are found to have a coarse porphyritic texture and calcic composition (80 normative mol percent An) similar to those of other Archean anorthosite complexes. Chemical similarities indicate that the gabbro and mafic to felsic metavolcanic formations associated with the anorthosite complex may be comagmatic with it, while the absence of ultramafic material and the bulk composition of the comagmatic basalt (about 20 wt percent Al2O3) suggest that much of the original comagmatic material has been separated.

Ashwal, L. D.↗