Viking: Mars atmospheric water vapor mapping experiment--preliminary report of results

Observations made from the Viking I orbiter show very little water vapor in the Mars atmosphere in the southern hemisphere (0 to 3 precipitable micrometers) with a gradual increase across the equator to northern latitudes. Maximum amounts between 20 and 30 micrometers have been observed in the short period covered by the observations to date. The season, northern midsummer, corresponds to the beginning of the water vapor cycle in that hemisphere. A strong repetitive diurnal cycling between the solid and vapor phases is observed at a site to the east of the Tharsis Ridge at 10 degrees north latitude; the vapor lies close to the martian surface and is most probably in saturation equilibrium with a surface haze or fog throughout much of the day.     

Detection of Water Vapor in Halley's Comet

Gaseous, neutral H(2)O was detected in the coma of comet Halley on 22.1 and 24.1 December 1985 Universal Time. Nine spectral lines of thev(3) band (2.65 micrometers) were found by means of a Fourier transform spectrometer (lambda/triangle uplambda approximately 10(5)) on the NASA-Kuiper Airborne Observatory. The water production rate was approximately 6 x 10(28) molecules per second on 22.1 December and 1.7 x 10(29) molecules per second on 24.1 December UT. The numbers of spectral lines and their intensities are in accord with nonthermal-equilibrium cometary models. Rotational populations are derived from the observed spectral line intensities and excitation conditions are discussed. The ortho-para ratio was found to be 2.66+/-0.13, corresponding to a nuclear-spin temperature of 32 K (+5 K, -2 K), possibly indicating that the observed water vapor originated from a low-temperature ice.     

Spectroscopic observations of bright and dark emission features on the night side of venus

Near-infrared spectra of a bright and a dark thermal emission feature on the night side of Venus have been obtained from 2.2 to 2.5 micrometers (microm) at a spectral resolution of 1200 to 1500. Both bright and dark features show numerous weak absorption bands produced by CO(2), CO, water vapor, and other gases. The bright feature (hot spot) emits more radiation than the dark feature (cold spot) throughout this spectral region, but the largest contrasts occur between 2.21 and 2.32 microm, where H(2)SO(4) clouds and a weak CO(2) band provide the only known sources of extinction. The contrast decreases by 55 to 65 percent at wavelengths longer than 2.34 microm, where CO, clouds, and water vapor also absorb and scatter upwelling radiation. This contrast reduction may provide direct spectroscopic evidence for horizontal variations in the water vapor concentrations in the Venus atmosphere at levels below the cloud tops.     

The role of the tropical super greenhouse effect in heating the ocean surface

Measurements made by a Fourier transform infrared (FTIR) spectroradiometer operating in the middle infrared (5 to 20 micrometers, with a spectral resolution of one inverse centimeter) imply that there is an anomalously large greenhouse effect over equatorial oceans that is caused by water vapor. As sea-surface temperature increased from 297 to 303 degrees kelvin, the net infrared cooling at the surface decreased by 30 to 50 watts per square meter. Thus, according to the FTIR data, the super greenhouse effect that had been inferred from satellite measurements contributes directly to radiative heating of the sea surface. The data demonstrate that most of this heating occurs in the middle infrared by means of the continuum emission window of water vapor and that tropical deep convection contributes substantially to this super greenhouse effect.     

First results from the large probe infrared radiometer experiment

During the descent to the surface of Venus, the large probe infrared radiometer measured the net thermal radiative flux in several spectral bandpasses. Preliminary analysis has permitted us to estimate (i) the infrared extinction coefficient profile attributable to aerosols, with respect to their visible profile, in the upper atmosphere of Venus and (ii) the water vapor mixing ratio below the clouds. An indication of the composition of a multicomponent cloud is seen in the data from the spectral bandpass from 6 to 7 micrometers.     

Galileo infrared imaging spectroscopy measurements at venus

During the 1990 Galileo Venus flyby, the Near Infaied Mapping Spectrometer investigated the night-side atmosphere of Venus in the spectral range 0.7 to 5.2 micrometers. Multispectral images at high spatial resolution indicate substanmial cloud opacity variations in the lower cloud levels, centered at 50 kilometers altitude. Zonal and meridional winds were derived for this level and are consistent with motion of the upper branch of a Hadley cell. Northern and southern hemisphere clouds appear to be markedly different. Spectral profiles were used to derive lower atmosphere abundances of water vapor and other species.     

Discovery of natural gain amplification in the 10-micrometer carbon dioxide laser bands on Mars: a natural laser

Fully resolved intensity profiles of various lines in the carbon dioxide band at 10.4 micrometers have been measured on Mars with an infrared heterodyne spectrometer. Analysis of the line shapes shows that the Mars atmosphere exhibits positive gain in these lines. The detection of natural optical gain amplification enables identification of these lines as a definite natural laser.     

Detection of the water reservoir in a forming planetary system

Icy bodies may have delivered the oceans to the early Earth, yet little is known about water in the ice-dominated regions of extrasolar planet-forming disks. The Heterodyne Instrument for the Far-Infrared on board the Herschel Space Observatory has detected emission lines from both spin isomers of cold water vapor from the disk around the young star TW Hydrae. This water vapor likely originates from ice-coated solids near the disk surface, hinting at a water ice reservoir equivalent to several thousand Earth oceans in mass. The water's ortho-to-para ratio falls well below that of solar system comets, suggesting that comets contain heterogeneous ice mixtures collected across the entire solar nebula during the early stages of planetary birth.     

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 ofHDO near 3.7 micrometers in the planet's spectrum. The ratio of deuterium to hydrogen is (9 +/- 4) x 10(-4); the abundance of H(2)0 was derived from lines near 1.1 micrometers. This ratio is enriched on Mars over the teiluric value by a factor of6 +/- 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.     

Polycrystalline CVD Diamond Films with High Electrical Mobility

Advances in the deposition process have led to dramatic improvements in the electronic properties of polycrystalline diamond films produced by chemical vapor deposition (CVD). It is now possible to produce CVD diamond with properties approaching those of IIa natural diamonds. The combined electron-hole mobility, as measured by transient photoconductivity at low carrier density, is 4000 square centimeters per volt per second at an electric field of 200 volts per centimeter and is comparable to that of the best single-crystal IIa natural diamonds. Carrier lifetimes measured under the same conditions are 150 picoseconds for the CVD diamond and 300 picoseconds for single-crystal diamond. The collection distance at a field of 10 kilovolts per centimeter is 15 micrometers for the CVD diamond as compared to 30 micrometers for natural diamonds. The electrical qualities appear to correlate with the width of the diamond Raman peak. Also, although the collection distance at the highest fields in the films nearly equals the average grain size, there is no evidence of deleterious grain boundary effects.     

Vertical distribution of water in the atmosphere of venus: a simple thermochemical explanation

Several lines of evidence concerning the vertical abundance profile of water in the atmosphere of Venus lead to strikingly unusual distributions (the water vapor abundance decreases sharply in the immediately vicinity of the surface) or to serious conflicts in the profiles (different infrared bands suggest water abundances that are discrepant by a factor of 2.5 to 10). These data sets can be reconciled if (i) water molecules associate with carbon dioxide and sulfur trioxide to make gaseous carbonic acid and sulfuric acid in the lower atmosphere, and (ii) the discrepant 0.94-micrometer water measurements are due to gaseous sulfuric acid, requiring it to be a somewhat stronger absorber than water vapor inthis wavelength region. A mean total water abundance of 50 +/- 20 parts per million and a near-surface free water vapor abundance of 10 +/- 4 parts per million are derived.     

Retention of plutonium and americium by rock

The relative migration ratio of plutonium in various rocks is approximately 100 micrometers per meter of waterflow; the corresponding migration ratio for americium is about 500 micrometers per meter of water flow. Under these conditions radioactive decay will have taken place to such an extent that little plutonium and americium can reach the external environment from a well-designed and isolated geological repository site.     

Macroscopic hierarchical surface patterning of porphyrin trimers via self-assembly and dewetting

The use of bottom-up approaches to construct patterned surfaces for technological applications is appealing, but to date is applicable to only relatively small areas (approximately 10 square micrometers). We constructed highly periodic patterns at macroscopic length scales, in the range of square millimeters, by combining self-assembly of disk-like porphyrin dyes with physical dewetting phenomena. The patterns consisted of equidistant 5-nanometer-wide lines spaced 0.5 to 1 micrometers apart, forming single porphyrin stacks containing millions of molecules, and were formed spontaneously upon drop-casting a solution of the molecules onto a mica surface. On glass, thicker lines are formed, which can be used to align liquid crystals in large domains of square millimeter size.     

Synthesis of large arrays of well-aligned carbon nanotubes on glass

Free-standing aligned carbon nanotubes have previously been grown above 700 degreesC on mesoporous silica embedded with iron nanoparticles. Here, carbon nanotubes aligned over areas up to several square centimeters were grown on nickel-coated glass below 666 degreesC by plasma-enhanced hot filament chemical vapor deposition. Acetylene gas was used as the carbon source and ammonia gas was used as a catalyst and dilution gas. Nanotubes with controllable diameters from 20 to 400 nanometers and lengths from 0. 1 to 50 micrometers were obtained. Using this method, large panels of aligned carbon nanotubes can be made under conditions that are suitable for device fabrication.     

Large-Scale Synthesis of Aligned Carbon Nanotubes

Large-scale synthesis of aligned carbon nanotubes was achieved by using a method based on chemical vapor deposition catalyzed by iron nanoparticles embedded in mesoporous silica. Scanning electron microscope images show that the nanotubes are approximately perpendicular to the surface of the silica and form an aligned array of isolated tubes with spacings between the tubes of about 100 nanometers. The tubes are up to about 50 micrometers long and well graphitized. The growth direction of the nanotubes may be controlled by the pores from which the nanotubes grow.     

Direct synthesis of long single-walled carbon nanotube strands

In the processes that are used to produce single-walled nanotubes (electric arc, laser ablation, and chemical vapor deposition), the typical lengths of tangled nanotube bundles reach several tens of micrometers. We report that long nanotube strands, up to several centimeters in length, consisting of aligned single-walled nanotubes can be synthesized by the catalytic pyrolysis of n-hexane with an enhanced vertical floating technique. The long strands of nanotubes assemble continuously from arrays of nanotubes, which are intrinsically long.     

The surface composition of charon: tentative identification of water ice

The 3 March 1987 Charon occultation by Pluto was observed in the infrared at 1.5, 1.7, 2.0, and 2.35 micrometers. Subtraction of fluxes measured between second and third contacts from measurements made before and after the event has yielded individual spectral signatures for each body at these wavelengths. Charon's surface appears depleted in methane relative to Pluto. Constancy of flux at 2.0 micrometers throughout the event shows that Charon is effectively black at this wavelength, which is centered on a very strong water absorption band. Thus, the measurements suggest the existence of water ice on Pluto's moon.     

Room-temperature ultraviolet nanowire nanolasers

Room-temperature ultraviolet lasing in semiconductor nanowire arrays has been demonstrated. The self-organized, <0001> oriented zinc oxide nanowires grown on sapphire substrates were synthesized with a simple vapor transport and condensation process. These wide band-gap semiconductor nanowires form natural laser cavities with diameters varying from 20 to 150 nanometers and lengths up to 10 micrometers. Under optical excitation, surface-emitting lasing action was observed at 385 nanometers, with an emission linewidth less than 0.3 nanometer. The chemical flexibility and the one-dimensionality of the nanowires make them ideal miniaturized laser light sources. These short-wavelength nanolasers could have myriad applications, including optical computing, information storage, and microanalysis.     

Exposed water ice deposits on the surface of comet 9P/Tempel 1

We report the direct detection of solid water ice deposits exposed on the surface of comet 9P/Tempel 1, as observed by the Deep Impact mission. Three anomalously colored areas are shown to include water ice on the basis of their near-infrared spectra, which include diagnostic water ice absorptions at wavelengths of 1.5 and 2.0 micrometers. These absorptions are well modeled as a mixture of nearby non-ice regions and 3 to 6% water ice particles 10 to 50 micrometers in diameter. These particle sizes are larger than those ejected during the impact experiment, which suggests that the surface deposits are loose aggregates. The total area of exposed water ice is substantially less than that required to support the observed ambient outgassing from the comet, which likely has additional source regions below the surface.     

海南岛地基GPS遥感水汽研究及与气象要素的相关分析

利用2005年11月海南岛地基GPS水汽观测资料与气象观测资料分析了GPS反演水汽与气象因子的相关关系,结果显示,GPS反演的水汽结果与探空资料计算的水汽一致性很好,与地面水汽压、相对湿度正相关,与降水量、云量、能见度等相关性不强。