First International Conference on Laboratory Research for Planetary Atmospheres

Proceedings of the First International Conference on Laboratory Research for Planetary Atmospheres are presented. The covered areas of research include: photon spectroscopy, chemical kinetics, thermodynamics, and charged particle interactions. This report contains the 12 invited papers, 27 contributed poster papers, and 5 plenary review papers presented at the conference. A list of attendees and a reprint of the Report of the Subgroup on Strategies for Planetary Atmospheres Exploration (SPASE) are provided in two appendices

Emission from Water Vapor and Absorption from Other Gases at 5-7.5 Microns in Spitzer-IRS Spectra of Protoplanetary Disks

We present spectra of 13 T Tauri stars in the Taurus-Auriga star-forming region showing emission in Spitzer Space Telescope Infrared Spectrograph (IRS) 5-7.5 micron spectra from water vapor and absorption from other gases in these stars' protoplanetary disks. Seven stars' spectra show an emission feature at 6.6 microns due to the nu_2 = 1-0 bending mode of water vapor, with the shape of the spectrum suggesting water vapor temperatures > 500 K, though some of these spectra also show indications of an absorption band, likely from another molecule. This water vapor emission contrasts with the absorption from warm water vapor seen in the spectrum of the FU Orionis star V1057 Cyg. The other six of the thirteen stars have spectra showing a strong absorption band, peaking in strength at 5.6-5.7 microns, which for some is consistent with gaseous formaldehyde (H2CO) and for others is consistent with gaseous formic acid (HCOOH). There are indications that some of these six stars may also have weak water vapor emission. Modeling of these stars' spectra suggests these gases are present in the inner few AU of their host disks, consistent with recent studies of infrared spectra showing gas in protoplanetary disks.Comment: 33 pages, 9 figures, to appear in the 20 August, 2014, V791 - 2 issue of the Astrophysical Journa

Photochemical modeling of CH_3 abundances in the outer solar system

Recent measurements of methyl radicals (CH_3) in the upper atmospheres of Saturn and Neptune by the Infrared Space Observatory (ISO) provide new constraints to photochemical models of hydrocarbon chemistry in the outer solar system. The derived column abundances of CH_3 on Saturn above 10 mbar and Neptune above the 0.2 mbar pressure level are (2.5–6.0) × 10^(13) cm^(−2) and (0.7–2.8) × 10^(13) cm^(−2), respectively. We use the updated Caltech/Jet Propulsion Laboratory photochemical model, which incorporates hydrocarbon photochemistry, vertical molecular and bulk atmospheric eddy diffusion, and realistic radiative transfer modeling, to study the CH_3 abundances in the upper atmosphere of the giant planets and Titan. We identify the key reactions that control the concentrations of CH_3 in the model, such as the three-body recombination reaction, CH_3 + CH_3 + M → C_2H_6 + M. We evaluate and extrapolate the three-body rate constant of this reaction to the low-temperature limit (1.8×10^(−16) T^(−3.75) e^(−300/T), T<300 K) and compare methyl radical abundances in five atmospheres: Jupiter, Saturn, Uranus, Neptune, and Titan. The sensitivity of our models to the rate coefficients for the reactions H + CH_3 + M → CH_4 + M, H + C_2H_3 → C_2H_2 + H_2, ^1CH_2 + H_2 → CH_3 + H, and H + C_2H_5 → 2 CH_3, the branching ratios of CH_4 photolysis, vertical mixing in the five atmospheres, and Lyman α photon enhancement at the orbit of Neptune have all been tested. The results of our model CH_3 abundances for both Saturn (5.1×10^(13) cm^(−2)) and Neptune (2.2×10^(13) cm^(−2)) show good agreement with ISO Short Wavelength Spectrometer measurements. Using the same chemical reaction set, our calculations also successfully generate vertical profiles of stable hydrocarbons consistent with Voyager and ground-based measurements in these outer solar system atmospheres. Predictions of CH_3 column concentrations (for p≤0.2 mbar) in the atmospheres of Jupiter (3.3×10^(13) cm^(−2)), Uranus (2.5×10^(12) cm^(−2)), and Titan (1.9×10^(15) cm^(−2)) may be checked by future observations

Near-Infrared Spectroscopy of Trojan Asteroids: Evidence for Two Compositional Groups

The Trojan asteroids remain quite poorly understood, yet their physical properties provide unique perspective on chemical and dynamical processes that shaped the Solar System. The current study was undertaken to investigate surface compositions of these objects. We present 66 new near-infrared (NIR; 0.7 to 2.5 microns) spectra of 58 Trojans, including members of both the leading and trailing swarms. We also include in the analysis previously published NIR spectra of 13 Trojans (3 of which overlap with the new sample). This data set permits not only a direct search for compositional signatures, but also a search for patterns that may reveal clues to the origin of the Trojans. We do not report any confirmed absorption features in the new spectra. Analysis of the spectral slopes, however, reveals an interesting bimodality among the NIR data. The two spectral groups identified appear to be equally abundant in the leading and trailing swarms. The spectral groups are not a result of family membership; they occur in the background, non-family population. The average albedos of the two groups are the same within uncertainties (0.051\pm0.016 and 0.055\pm0.016). No correlations between spectral slope and any other physical or orbital parameter are detected, with the exception of a possible weak correlation with inclination among the less-red spectral group. Synthesizing these results with previously published properties, we conclude that the two spectral groups represent objects with different intrinsic compositions. We further suggest that while the less-red group originated near Jupiter or in the main asteroid belt, the redder spectral group originated farther out in the Solar System. If correct, the Trojan swarms offer the most readily accessible large reservoir of Kuiper Belt material as well as a unique reservoir for the study of material from the middle part of the solar nebula.Comment: Astronomical Journal, in press 38 manuscript pages 3 tables 7 Figures (color online, B&W for print) 1 appendi

NASA scientific and technical publications: A catalog of special publications, reference publications, conference publications, and technical papers, 1987-1990

This catalog lists 783 citations of all NASA Special Publications, NASA Reference Publications, NASA Conference Publications, and NASA Technical Papers that were entered into NASA Scientific and Technical Information Database during the year's 1987 through 1990. The entries are grouped by subject category. Indexes of subject terms, personal authors, and NASA report numbers are provided

NASA upper atmosphere research program: Research summaries, 1990 - 1991. Report to the Congress and the Environmental Protection Agency

The objectives, status, and accomplishments of the research tasks supported under the NASA Upper Atmosphere Research Program (UARP) are presented. The topics covered include the following: balloon-borne in situ measurements; balloon-borne remote measurements; ground-based measurements; aircraft-borne measurements; rocket-borne measurements; instrument development; reaction kinetics and photochemistry; spectroscopy; stratospheric dynamics and related analysis; stratospheric chemistry, analysis, and related modeling; and global chemical modeling

Atmospheric Chemistry and Transport Modeling in the Outer Solar System

This thesis consists of 1-D and 2-D photochemical dynamical modeling in the upper atmospheres of outer planets. For 1-D modeling, a unified hydrocarbon photochemical model has been studied in Jupiter, Saturn, Uranus, Neptune, and Titan, by comparing with the Voyager observations, and the recent measurements of methyl radicals by ISO in Saturn and Neptune. The CH_3 observation implies a kinetically sensitive test to the measured and estimated hydrocarbon rate constants at low temperatures. We identify the key reactions that control the concentrations of CH_3 in the model, such as the three-body recombination reaction, CH_3 + CH_3 + M → C_(2)H_6 + M, and the recycling reaction H + CH_3 + M →CH_4 + M. The results show reasonable agreement with ISO values. In Chapter 4, the detection of PH_3 in the lower stratosphere and upper troposphere of Jupiter has provided a photochemical-dynamical coupling model to derive the eddy diffusion coefficient in the upper troposphere of Jupiter. Using a two-layers photochemical model with updated photodissociation cross-sections and chemical rate constants for NH_3 and PH_3, we find that the upper tropospheric eddy diffusion coefficient &lt;10^5 cm^2 sec^(-1) and the deeper tropospheric value &gt;10^6 cm^2 sec^(-1) are required to match the derived PH_3 vertical profile by the observation. The best-fit functional form derivation of eddy diffusion coefficient in the upper troposphere of Jupiter above 400 mbar is K = 2.0 x 10^4 (n/2.2 x 10^19)^(-0.5)cm^2 sec^(-1). On the other hand, Chapter 5 demonstrates a dynamical-only 2-D model of C_(2)H_6 providing a complete test for the current 2-D transport models in Jovian lower stratosphere and upper troposphere (270 to 0.1 mbar pressure levels). Different combinations of residual advection, horizontal eddy dispersion, and vertical eddy mixing are examined at different latitudes.</p

Evidence of panspermia: from astronomy to meteorites

The theory of cometary panspermia is tested in the wake of two reported falls in Tissint, Morocco on July 18, 2011 and in the central province of Polonnaruwa, Sri Lanka on December 29, 2012. Samples of the Tissint and Polonnaruwa stones were studied using a variety of laboratory procedures and equipment including ICP-OES, GC-MS, SEM, EDAX, CHN, FTIR, Raman Spectroscopy, XRD and Optical Spectroscopy. Results of Tissint show the presence of several 5-50μm pyrite grains rimmed by a layer of reduced organic carbon with graphitisation levels consistent with other Martian meteorites. A complex precursor carbon inventory is demonstrated with peak temperatures ~ 250 OC and elemental ratios typical of high volatility bituminous coals. A theoretical model of the ecology of arsenic on early Mars is then developed and discussed involving microbial reduction of Fe-oxides. This hypothesis is shown to be supported by SEM observations of spherical chains of pits, with morphologies distinct from abiotic alteration features but closely comparable to biologically mediated microstructures created by Fe- and S-oxidising microbes. The contribution of core-mantle grains to mid-IR emission features is then modelled using extinction and scattering efficiencies for composite spheres based on the Guttler extension of the Mie formulae. Results show that kerogen-pyrite grains closely adhere to observed 9-13μm emission characteristics observed in the Trapezium nebula. Results of studies on Polonnaruwa show a highly porous Si-K-rich, Al-depleted, amorphous melt enclosing trace (commonly <1μm) anorthoclase, albite, anorthite and quartz. Bound H2O < 0.03wt% indicates origin from hypervelocity impact. SEM analysis revealed several fossil microorganisms similar to acritarchs, hystrichospheres and diatoms. Geologic age of the stones is determined by N/C atomic ratio depletion that indicate the presence of embedded fossil remains that date back to at least ~300 Ma. Triple oxygen isotope analysis provide values of Δ17O = - 0.335 with δ17O = 8.978 ± 0.050 and δ18O = 17.816 ± 0.100 that is shown to be consistent with non-terrestrial sources. Results are seen to substantially support the theory of cometary panspermia