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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on NiH36(C5N)12 by Materials Project

Ni(NH3)6(C)60(NH3)6 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of six ammonia molecules, one fullerene molecule, and one Ni(NH3)6 cluster. In the Ni(NH3)6 cluster, Ni is bonded in an octahedral geometry to six N atoms. There are a spread of Ni–N bond distances ranging from 2.15–2.19 Å. There are three inequivalent N sites. In the first N site, N is bonded in a distorted trigonal non-coplanar geometry to one Ni and three H atoms. There is two shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the second N site, N is bonded in a distorted trigonal non-coplanar geometry to one Ni and three H atoms. There is two shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the third N site, N is bonded in a distorted trigonal non-coplanar geometry to one Ni and three H atoms. There is two shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. There are nine inequivalent H sites. In the first H site, H is bonded in a single-bond geometry to one N atom. In the second H site, H is bonded in a single-bond geometry to one N atom. In the third H site, H is bonded in a single-bond geometry to one N atom. In the fourth H site, H is bonded in a single-bond geometry to one N atom. In the fifth H site, H is bonded in a single-bond geometry to one N atom. In the sixth H site, H is bonded in a single-bond geometry to one N atom. In the seventh H site, H is bonded in a single-bond geometry to one N atom. In the eighth H site, H is bonded in a single-bond geometry to one N atom. In the ninth H site, H is bonded in a single-bond geometry to one N atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li2P7(H3N)9 by Materials Project

(Li(NH3)4)2(P)7NH3 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two ammonia molecules, fourteen phosphine molecules, and four Li(NH3)4 clusters. In two of the Li(NH3)4 clusters, Li1+ is bonded in a tetrahedral geometry to four N3- atoms. There are a spread of Li–N bond distances ranging from 2.07–2.09 Å. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded to one Li1+ and three H+0.78+ atoms to form distorted corner-sharing NLiH3 tetrahedra. There is one shorter (1.02 Å) and two longer (1.03 Å) N–H bond length. In the second N3- site, N3- is bonded to one Li1+ and three H+0.78+ atoms to form distorted corner-sharing NLiH3 tetrahedra. There is one shorter (1.02 Å) and two longer (1.03 Å) N–H bond length. In the third N3- site, N3- is bonded to one Li1+ and three H+0.78+ atoms to form distorted corner-sharing NLiH3 tetrahedra. There is two shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the fourth N3- site, N3- is bonded to one Li1+ and three H+0.78+ atoms to form distorted corner-sharing NLiH3 tetrahedra. There is one shorter (1.02 Å) and two longer (1.03 Å) N–H bond length. There are twelve inequivalent H+0.78+ sites. In the first H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the second H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the third H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the fourth H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the fifth H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the sixth H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the seventh H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the eighth H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the ninth H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the tenth H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the eleventh H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the twelfth H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In two of the Li(NH3)4 clusters, Li1+ is bonded in a tetrahedral geometry to four N3- atoms. There are two shorter (2.06 Å) and two longer (2.08 Å) Li–N bond lengths. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded to one Li1+ and three H+0.78+ atoms to form distorted corner-sharing NLiH3 tetrahedra. There is one shorter (1.02 Å) and two longer (1.03 Å) N–H bond length. In the second N3- site, N3- is bonded to one Li1+ and three H+0.78+ atoms to form distorted corner-sharing NLiH3 tetrahedra. There is two shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the third N3- site, N3- is bonded to one Li1+ and three H+0.78+ atoms to form distorted corner-sharing NLiH3 tetrahedra. There is two shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the fourth N3- site, N3- is bonded to one Li1+ and three H+0.78+ atoms to form distorted corner-sharing NLiH3 tetrahedra. There is two shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. There are twelve inequivalent H+0.78+ sites. In the first H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the second H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the third H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the fourth H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the fifth H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the sixth H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the seventh H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the eighth H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the ninth H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the tenth H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the eleventh H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom. In the twelfth H+0.78+ site, H+0.78+ is bonded in a single-bond geometry to one N3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnH36(C5N)12 by Materials Project

Mn(NH3)6(C)60(NH3)6 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of six ammonia molecules, one fullerene molecule, and one Mn(NH3)6 cluster. In the Mn(NH3)6 cluster, Mn is bonded in an octahedral geometry to six N atoms. There are a spread of Mn–N bond distances ranging from 2.33–2.40 Å. There are three inequivalent N sites. In the first N site, N is bonded in a distorted trigonal non-coplanar geometry to one Mn and three H atoms. There is one shorter (1.02 Å) and two longer (1.03 Å) N–H bond length. In the second N site, N is bonded in a distorted trigonal non-coplanar geometry to one Mn and three H atoms. There is one shorter (1.02 Å) and two longer (1.03 Å) N–H bond length. In the third N site, N is bonded in a distorted trigonal non-coplanar geometry to one Mn and three H atoms. There is two shorter (1.03 Å) and one longer (1.04 Å) N–H bond length. There are nine inequivalent H sites. In the first H site, H is bonded in a single-bond geometry to one N atom. In the second H site, H is bonded in a single-bond geometry to one N atom. In the third H site, H is bonded in a single-bond geometry to one N atom. In the fourth H site, H is bonded in a single-bond geometry to one N atom. In the fifth H site, H is bonded in a single-bond geometry to one N atom. In the sixth H site, H is bonded in a single-bond geometry to one N atom. In the seventh H site, H is bonded in a single-bond geometry to one N atom. In the eighth H site, H is bonded in a single-bond geometry to one N atom. In the ninth H site, H is bonded in a single-bond geometry to one N atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiH42N14Cl3 by Materials Project

(Ti(NH3)8)2(NH3)12(Cl2)3 is Ammonia-derived structured and crystallizes in the monoclinic P2/c space group. The structure is zero-dimensional and consists of twelve ammonia molecules, six hydrochloric acid molecules, and two Ti(NH3)8 clusters. In each Ti(NH3)8 cluster, Ti3+ is bonded in a 8-coordinate geometry to eight N3- atoms. There are two shorter (2.29 Å) and six longer (2.30 Å) Ti–N bond lengths. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a trigonal non-coplanar geometry to one Ti3+ and three H1+ atoms. There are a spread of N–H bond distances ranging from 1.02–1.04 Å. In the second N3- site, N3- is bonded in a trigonal non-coplanar geometry to one Ti3+ and three H1+ atoms. There is two shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the third N3- site, N3- is bonded in a trigonal non-coplanar geometry to one Ti3+ and three H1+ atoms. There is one shorter (1.02 Å) and two longer (1.03 Å) N–H bond length. In the fourth N3- site, N3- is bonded in a trigonal non-coplanar geometry to one Ti3+ and three H1+ atoms. All N–H bond lengths are 1.03 Å. There are twelve inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the tenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the eleventh H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the twelfth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Innovative SCR Materials and System for Low Temperature - CRADA 350 (Abstract)

The aim of this CRADA is focused on providing a new enabling SCR catalyst system that will function at very high efficiency to attain the most demanding emissions regulations and thereby facilitate the market introduction of advanced powertrains that will support domestic energy independence and security. Future powertrains, that will be significantly more efficient than currently available technologies, will be needed by automotive manufacturers to meet rapidly increasing CAFE and GHG standards. However, these powertrains cannot enter into the US light duty vehicle market unless they are coupled with an aftertreatment system that will sufficiently remediate tailpipe emissions to meet EPA Tier III and California SULEV emissions standards. The low temperature exhaust associated with these powertrains is especially challenging for any current aftertreatment technology to meet these standards. The key focus of this CRADA is to further develop newly invented materials for the selective catalytic reduction (SCR) of NOx by ammonia (NH3) that show promise for significantly reducing ‘light-off’ temperatures compared to current commercial catalysts. Specifically, the goal of the proposed work is to achieve ‘light-off’ of NH3 SCR at 150 ºC in order to realize conversion efficiencies of 90% at these low temperatures. This will enable deployment of lean combustion powertrains with significantly increased fuel efficiencies but lower exhaust temperatures. To accomplish this overall goal, it will be essential to also identify an appropriate NH3 supply strategy for the SCR aftertreatment device that can controllably deliver NH3 at these low temperatures.

36 MATERIALS SCIENCE↗
NASA NTRS1974

The abundance of ammonia on Jupiter, Saturn and Titan

From recent spectra of Jupiter, Saturn and Titan in the 6450-A band of NH3, new values of the abundance of ammonia are derived for Jupiter and Saturn. NH3 abundances of 13 plus or minus 3 m-Am on Jupiter and 2 plus or minus 1 m-Am on Saturn were found. High resolution profiles of NH3 lines on Jupiter are used to estimate a pressure of 2.1 atm at the line formation level in the Jovian atmosphere. In the case of Titan, an NH3 abundance of less than 2 m-Am was found. The implications of these results are discussed.

Encrenaz, T.↗
NASA NTRS1976

Analysis of ECLSS performance during reentry after loss of one ammonia tank

An analysis was performed to determine whether, in case of a loss of one of the ammonia tanks, the Ammonia Boiler System can provide adequate heat rejection for the orbiter ECLSS during reentry. Results indicate that temperatures can be maintained as long as NH3 is available, but that one tank does not contain sufficient NH3 to complete all missions. A recommendation is made to investigate incorporation of onboard NH3 quantity calculations, and/or addition of a third NH3 tank.

Steines, G. J.↗
NASA NTRS1975

The thermal structure of Jupiter. II - Observations and analysis of 8-14 micron radiation

Observations of Jovian limb structure at 8.11 and 8.45 microns are reported. These are used along with other limb structure and spectral data in the 8-14 micron region to derive a model of the thermal and cloud structure within the 1.0-0.01 bar pressure regime. The temperature is about 165 K at 1.00 bar, 108 K at 0.10 bar, and 143 K at 0.03 bar. In zones, an optically opaque cloud of NH3 exists near the 143 K (0.60 bar) level. A partly transparent haze of solid NH3 particles overlies the cloud. Belts are free of the cloud and have a much lower abundance of NH3 haze than the zones. The data are consistent with an NH3 gas abundance defined by saturation equilibrium, with a mixing ratio of 0.00015 deep in the atmosphere, and with a CH4 mixing ratio of 0.002, about three times the currently accepted value.

Orton, G. S.↗
NASA NTRS1980

The vertical distribution of tropospheric ammonia

A one-dimensional tropospheric photochemical model is used to simulate measured profiles of NH3 obtained with the Infrared Heterodyne Radiometer. The relative roles of homogeneous loss, heterogeneous loss, and vertical eddy transport are discussed in terms of selecting parameters which best fit the measurements. The best fit was obtained for a vertical eddy diffusion coefficient of 200,000/sq cm per sec or greater (corresponding to a characteristic vertical transport time in excess of about 35 days), and a characteristic heterogeneous loss time in excess of 10 days. The characteristic homogeneous chemical loss time was found to be about 40 days at the surface and decreased to about 180 days at 10 km, and not very sensitive to model chemical perturbations. Increased ground-level concentrations of NH3 to about 10 ppb, compared to background surface concentrations of about 1 ppb, were measured several weeks after application of ammonium nitrate fertilizer. This suggests that the volatilization of ammonium nitrate fertilizer is rapid, and an important source of NH3. Because of the characteristic times for the loss mechanisms, synoptic time-scale phenomena may play an important role in determining the tropospheric distribution of NH3 concentrations.

Levine, J. S.↗
NASA NTRS1980

High spatial and spectral resolution 10-micron observations of Jupiter

Ten-micrometer spectra of the North Tropical Zone, North Equatorial Belt, and Great Red Spot at a spectral resolution of 1.1/cm are compared to synthetic spectra. These ground-based spectra were obtained simultaneously with the Voyager 1 encounter with Jupiter in March, 1979. The NH3 vertical distribution is found to decrease with altitude significantly faster than the saturated vapor pressure curve and is different for the three observed regions. Spatial variability in the NH3 mixing ratio could be caused by changes in the amount of NH3 condensation or in the degree of the NH3 photolysis. The C2H6 emission at 12 microns has approximately the same strength at the North Tropical Zone and North Equatorial Belt, but it is 30% weaker at the Great Red Spot. A cooler temperature inversion or a smaller abundance of C2H6 could explain the lower C2H6 emission over the Great Red Spot.

Tokunaga, A. T.↗
NASA NTRS1983

Longitudinal variability of methane and ammonia bands on Jupiter. II - Temporal variations

A set of spectra has been obtained of the Jovian equatorial zone central meridian 6190 A CH4 and 6450 A NH3 bands on the nights of February 26, 27, and 28, 1980, a year after the data reported by Cochran and Cochran (1980), in order to check the previous results and search for possible temporal variations. The new data confirm the results of the previous study. A correlation of the NH3 and CH4 equivalent widths, as well as a lack of any strong correlation of red continuum reflectivity with equivalent width, are found. Longitude regions of larger or smaller than average equivalent width still seem to exist a year later, with some slight drift in longitude. An increase in the average CH4 and NH3 equivalent width over the entire planet was detected during the one year interval. This is easily understood as the result of a global decrease in the mean altitude of the NH3 cloud.

Cochran, W. D.↗
NASA NTRS1985

High Pressure Cosmochemistry of Major Planetary Interiors: Laboratory Studies of the Water-rich Region of the System Ammonia-water

The behavior of gas-ice mixtures in major planets at very high pressures was studied. Some relevant pressure-temperature-composition (P-T-X) regions of the hydrogen (H2)-helium (He)-water (H2O-ammonia (NH3)-methane (CH4) phase diagram were determined. The studies, and theoretical model, of the relevant phases, are needed to interpret the compositions of ice-gas systems at conditions of planetary interest. The compositions and structures of a multiphase, multicomponent system at very high pressures care characterized, and the goal is to characterize this system over a wide range of low and high temperatures. The NH3-H2O compositions that are relevant to planetary problems yet are easy to prepare were applied. The P-T surface of water was examined and the corresponding surface for NH3 was determined. The T-X diagram of ammonia-water at atmospheric pressure was studied and two water-rich phases were found, NH3-2H2O (ammonia dihydrate), which melts incongruently, and NH3.H2O (ammonia monohydrate), which is nonstoichiometric and melts at a higher temperature than the dihydrate. It is suggested that a P-T surface at approximately the monohydrate composition and the P-X surface at room temperature is determined.

Nicol, M.↗
NASA NTRS1985

Compatibility of grain-stabilized platinum with candidate propellants for resistojets

Resistojets are candidates for space station auxiliary propulsion, and should be characterized by both long life and multipropellant operations, requirements limited by available materials. Grain stabilized platinum is examined for use as a resistojet thruster material. Use of platinum in other applications indicates it can be used at moderately high temperatures for extended periods of time. Past results indicate that grain-stabilized platinum should be sufficiently inert in candidate propellant environments. Therefore, compatibility of platinum-yttria (P/Y2O3) and platinum-zirconia (Pt/ZrO2) with carbon dioxide, methane, hydrogen and ammonia is examined. A series of 1000 hr tests in CO2, H2, and NH3 is conducted at 1400 C and a series of 1000 hr tests in CH4 is conducted at about 500 C. Scanning electron microscopy, Auger electron spectroscopy and depth profiling analysis are then used to determine the effects of propellants on the material surface, to evaluate possible material contamination and to evaluate grain growth. The results indicate that there is carbon deposition on the surface of the Pt/Y2O3 and Pt/ZrO2 in both the CO2 and CH4 environments. In the H2 environment, the Pt/Y2O3 and Pt/ZrO2 specimen surfaces are roughened. After exposure to the NH3 environment, the Pt/Y2O3 and Pt/ZrO2 are roughened and pitted over the entire heated area with some pitted areas along the grain boundaries. SEM photos show grain growth in cross-sectional views of all the Pt/Y2O3 samples and the Pt/ZrO2 samples, except that tested in methane. Mass loss measurements indicate that Pt/Y2O3 and Pt/ZrO2 would last in excess of 200,000 hr in each propellant environment. However, in NH3 both Pt/Y2O3 and Pt/ZrO2 are severely pitted, with voids up to 50 percent into the material. Pt/Y2O3 and Pt/ZrO2 are not recommended for high temperature service in NH3.

Whalen, M. V.↗
NASA NTRS1989

Fabry-Perot observations of NH2 emission from Comet Halley

The (0,8,0) cometary NH2 band lines have been isolated from both cometary and terrestrial OI 6300 A OH emissions in Fabry-Perot spectra of the emissions of Comet Halley near 6300 A. On the assumption that the major source of NH2 is NH3, these NH2 measurements limit NH3's abundance relative to H2O. The results thus obtained are noted to depend on the NH2 (0,8,0) band fluorescence efficiency factor g(B); using the g(B) value of A'Hearn (1982), the NH3 abundance is found to be about 0.1 percent of that of H2O, while the g(B) value of Tegler and Wyckoff (1989) yields a figure of 0.4 percent. Both results indicate a low NH3 abundance relative to water on Comet Halley.

Magee-Sauer, K.↗
NASA NTRS1993

Possible solutions to the problem of channel formation on early Mars

A warm climate on early Mars would provide a natural, although not unique, explanation for the presence of fluvial networks on the ancient, heavily cratered terrains. Explaining how the climate could have been kept warm, however, is not easy. The idea that the global average surface temperature, T(sub s), could have been kept warm by a dense, CO2 atmosphere supplied by volcanism or impacts is no longer viable. It was shown that CO2 cloud formation should have kept T(sub s) well below freezing until approximately 2 b.y. ago, when the Sun had brightened to at least 86 percent of its present value. Warm equatorial regions on an otherwise cold planet seem unlikely because atmospheric CO2 would probably condense out at the poles. Warming by impact-produced dust in the atmosphere seems unlikely because the amount of warming expected for silicate dust particles is relatively small. Greenhouse warming by high altitude CO2 ice clouds seems unlikely because such are poor absorbers of infrared radiation at most wavelengths. Warming by atmospheric NH3 seems unlikely because NH3 is readily photodissociated and because N may have been in short supply as consequence of impact erosion and the high solubility of NH3. A brighter, mass-losing young Sun seems unlikely because stellar winds of the required strength were not observed on other solar-type stars. In short, most of the explanations for a warm Martian paleoclimate that were proposed in the past seem unlikely. One possibility that seems feasible from radiative/photochemical standpoint is that CH4 and associated hydrocarbon gases and particles contributed substantially to the greenhouse effect on early Mars. Methane is photochemically more stable than NH3 and the gases and particles that can be formed from it are all good absorbers of infrared radiation. The idea of a CH4-rich Martian paleoatmosphere was suggested a long time ago but has fallen out of favor because of perceived difficulties in maintaining a CH4-rich atmosphere. In particular, it is not obvious where the CH4 might come from, since volcanic gases (on Earth, at least) contain very little CH4. This difficulty could be largely overcome if early Mars was inhabited by microorganisms. Then, methanogenic bacteria living in sediments could presumably have supplied CH4 to the atmosphere in copious quantities.

Kasting, J. F.↗
NASA NTRS1994

Ammonia on the prebiotic Earth: Iron(II) reduction of nitrite

Theories for the origin of life require the availability of reduced nitrogen. In the non-reducing atmosphere suggested by geochemical evidence, production in the atmosphere and survival of NH3 against photochemical destruction are problematic. Electric discharges and impact shocks would produce NO rather than HCN or NH3. Conversion of NO to nitrous and nitric acid (by way of HNO) and precipitation in acid rain would provide a source of fixed nitrogen to the early ocean. One solution to the NH3 problem may have been the reduction of nitrite/nitrate in the ocean with aqueous ferrous iron, Fe(2+): 6Fe(+2) + 7 H2O + NO2(-) yields 3Fe2O3 + 11 H(+) + NH3. We have measured the kinetics of this reaction as a function of temperature, pH, and concentrations of salts, Fe(+2), and NO2(-). Cations (Na(+), Mg(2+), K(+)) and anions (Cl(-), Br(-), SO4(2-)) increase the rate by factors of 4 to 8. Although a competing pathway yields N2, the efficiency of the conversion of nitrite to ammonia ranges from 25% to 85%. Nitrate reduction was not consistently reproducible; however, when it was observed, its rate was slower by at least 8X than that of nitrite reduction. If the prebiotic atmosphere contained 0.2 to 10 atmospheres CO2 as suggested by Walker (1985), the Fe(+2) concentration and the rate would have been limited by siderite (FeCO3) solubility.

Summers, David P.↗
NASA NTRS1997

A 2000 Solar Mass Rotating Molecular Disk Around NGC 6334A

We present millimeter and centimeter wave spectroscopic observations of the H II region NGC 6334A. We have mapped the source in several transitions of CO, CS, and NH3. The molecular emission shows a distinct flattened structure in the east-west direction. This structure is probably a thick molecular disk or torus (2.2 x 0.9 pc) responsible for the bipolarity of the near-infrared (NIR) and radio continuum emission which extends in two "lobes" to the north and south of the shell-like H II region. The molecular disk is rotating from west to east (omega approximately equals 2.4 km/s.pc) about an axis approximately parallel to the radio and NIR emission lobes. By assuming virial equilibrium, we find that the molecular disk contains approximately 2000 solar mass. Single-component gas excitation model calculations show that the molecular gas in the disk is warmer and denser (T(sub k) approximately equals 60 K, n approximately equals 3000/cc) than the gas to the north and south (T(sub k) approximately equals 50 K, n approximately equals 400/cc). High resolution (approximately 5 sec) NH3 (3, 3) images of NGC 6334A reveal several small (approximately 0.1 pc) clumps, one of which lies southwest of the radio continuum shell, and is spatially coincident with a near-infrared source, IRS 20. A second NH3 clump is coincident with an H2O maser and the center of a molecular outflow. The dense gas tracers, CS J = 5 approaches 4 and 7 approaches 6, peak near IRS 20 and the H2O maser, not at NGC 6334A. IRS 20 has a substantial far-infrared (FIR) luminosity L(sub FIR) approximately 10(exp 5) solar luminosity, which indicates the presence of an O 7.5 star but has no detected radio continuum (F(sub 6 cm) < 0.02 Jy). The combination of dense gas, a large FIR luminosity and a lack of radio continuum can best be explained if IRS 20 is a protostar. A third clump of NH3 emission lies to the west of IRS 20 but is not associated with any other molecular or continuum features. The star formation activity in the region has moved west of NGC 6334A to IRS 20 and the H2O maser position. We suggest that NGC 6334A, IRS 20, and the H2O maser spot are part of a "protocluster" of stars which is condensing from the massive molecular disk. The similarity between the structure around NGC 6334A and other large (r approximately 1 pc), massive (M approximately 10(exp 3) solar mass), rotating disks (K3-50A and G10.6-0.4) suggests that this may be a common mechanism by which open clusters form.

Kraemer, Kathleen E.↗
NASA NTRS1998

Galileo Probe Measurements of Thermal and Solar Radiation Fluxes in the Jovian Atmosphere

The Galileo probe net flux radiometer (NFR) measured radiation fluxes in Jupiter's atmosphere from about 0.44 to 14 bars, using five spectral channels to separate solar and thermal components. Onboard calibration results confirm that the NFR responded to radiation approximately as expected. NFR channels also responded to a superimposed thermal perturbation, which can be approximately removed using blind channel measurements and physical constraints. Evidence for the expected NH3 cloud was seen in the spectral character of spin-induced modulations of the direct solar beam signals. These results are consistent with an overlying cloud of small NH3 ice particles (0.5-0.75 microns in radius) of optical depth 1.5-2 at 0.5 microns. Such a cloud would have so little effect on thermal fluxes that NFR thermal channels provide no additional constraints on its properties. However, evidence for heating near 0.45 bar in the NFR thermal channels would seem to require either an additional opacity source beyond this small-particle cloud, implying a heterogeneous cloud structure to avoid conflicts with solar modulation results, or a change in temperature lapse rate just above the probe measurements. The large thermal flux levels imply water vapor mixing ratios that are only 6% of solar at 10 bars, but possibly increasing with depth, and significantly subsaturated ammonia at pressures less than 3 bars. If deep NH3 mixing ratios at the probe entry site are 3-4 times ground-based inferences, as suggested by probe radio signal attenuation, then only half as much water is needed to match NFR observations. No evidence of a water cloud was seen near the 5-bar level. The 5-microns thermal channel detected the presumed NH4SH cloud base near 1.35 bars. Effects of this cloud were also seen in the solar channel upflux measurements but not in the solar net fluxes, implying that the cloud is a conservative scatterer of sunlight. The minor thermal signature of this cloud is compatible with particle radii near 3 gm, but it cannot rule out smaller particles. Deeper than about 3 bars, solar channels indicate unexpectedly large absorption of sunlight at wavelengths longer than 0.6 microns, which might be due to unaccounted-for absorption by NH3 between 0.65 and 1.5 microns.

Sromovsky, L. A.↗