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At least 757 records · Page 42
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NASA NTRS1989

The Allegheny Observatory search for planetary systems

The accomplishments of the observatory's search for planetary systems are summarized. Among these were the construction, implementation, and regular use of the Multichannel Astrometric Photometer (MAP), and the design, fabrication and use of the second largest refractor objective built since 1950. The MAP parallax and planetary observing programs are described. Various developments concerning alternate solid state photodetectors and telescope instrumentation are summarized. The extreme accuracy of the system is described in relation to a study of the position and velocity of the members of the open cluster Upgren 1. The binary star system stringently tests the theory of stellar evolution since it is composed of an evolved giant F5 III and a subgiant F5 IV star. A study that attempts to measure the luminosities, surface temperatures, and masses of these stars is discussed.

Gatewood, George D.↗
NASA NTRS1989

Microbial trace fossils in Antarctica and the search for evidence of early life on Mars

It is possible to hypothesize that, if microbial life evolved on early Mars, fossil remnants of these organisms may be preserved on the surface. However, the cooling and drying of Mars probably resembled a cold desert and such an environment is not suitable for the process of fossilization. The frigid Ross Desert of Antarctica is probably the closest terrestrial analog to conditions that may have prevailed on the surface of the cooling and drying Mars. In this desert, cryptoendolithic microbial communities live in the airspaces of porous rocks, the last habitable niche in a hostile outside environment. The organisms produce characteristic chemical and physical changes in the rock substrate. Environmental changes (deterioration of conditions) may result in the death of the community. Although no cellular structures are fossilized, the conspicuous changes in the rock substrate are preserved as trace fossils. Likewise, microbial trace fossils (without cellular structures) may also be preserved on Mars: Discontinuities in structure or chemistry of the rock that are independent of physical or chemical gradients may be of biological origin. Ross Desert trace fossils can be used as a model for planning search strategies and for instrument design to find evidence of past Martian life.

Friedmann, E. Imre↗
NASA NTRS1989

A search for biogenic trace gases in the atmosphere of Mars

The detection of certain trace gases in the atmosphere of Mars may serve as a possible indicator of microbial life on the surface of Mars. Candidate biogenic gases include methane CH4, ammonia NH3, nitrous oxide N2O, and several reduced sulfur species. Chemical thermodynamic equilibrium and photochemical calculations preclude the presence of these gases in any measurable concentrations in the atmosphere of Mars in the absence of biogenic production. A search for these gases utilizing either high resolution (spectral and spatial) spectroscopy from a Mars orbiter, such as the Observer, and or in situ measurements from a Mars lander or rover, is proposed.

Levine, Joel S.↗
NASA NTRS1989

Phylogenetic perspective and the search for life on earth and elsewhere

Any search for microbial life on Mars cannot rely upon cultivation of indigenous organisms. Only a minority of even terrestrial organisms that are observed in mixed, naturally-occurring microbial populations can be cultivated in the laboratory. Consequently, methods are being developed for analyzing the phylogenetic affiliations of the constituents of natural microbial populations without the need for their cultivation. This is more than an exercise in taxonomy, for the extent of phylogenetic relatedness between unknown and known organisms is some measure of the extent of their biochemical commonalities. In one approach, total DNA is isolated from natural microbial populations and 16S rRNA genes are shotgun cloned for rapid sequence determinations and phylogenetic analyses. A second approach employs oligodeoxynucleotide hybridization probes that bind to phylogenetic group-specific sequences in 16S rRNA. Since each actively growing cell contains about 104 ribosomes, the binding of the diagnostic probes to single cells can be visualized by radioactivity or fluorescence. The application of these methods and the use of in situ cultivation techniques is illustrated using submarine hydrothermal vent communities. Recommendations are made regarding planning toward future Mars missions.

Pace, Norman R.↗
NASA NTRS1988

A search for water on the moon at the Reiner Gamma Formation - A possible site of cometary coma impact

Earth-based telescopic measurements of the Reiner Gamma Formation in the 3-micron region were made to search for evidence of water at this proposed site of cometary interaction with the lunar surface. Comparison of the spectra of Reiner Gamma and laboratory measurements of a variety of minerals with adsorbed water or structural OH(-) show that there is no evidence for water at the locations measured. While these measurements rule out the presence of abundant bound H2O at these locations, they do not exclude the presence of OH(-) bearing minerals that have absorptions not detectable through the wet terrestrial atmosphere. The possible effects of high lunar temperatures on the reflectance spectra were examined, and it was concluded that these effects would not obscure a bound water absorption if it were present. Upper limits on the amount of water that could be present at the locations observed and remain undetected are 2.25 average wt pct for a mixture consisting of discrete patches of water-bearing and water-free minerals and 0.01 wt pct for an intimate mixture of these two materials.

Roush, Ted L.↗
NASA NTRS1988

Mars - Satellite and ring search from Viking

Viking Orbiter 1 imaging data were used in a search for possible satellites and rings of Mars in 1980, giving attention to a region within the Phobos orbit and + or - 350 km about the Martian equatorial plane. After picture processing, no images other than stars and Phobos itself were found to be a few brightnesses (or more) above their surrounding, as would be expected in the case of a point-spread, 'smeared' image of either satellites or rings. There is therefore no evidence of any such phenomenon in the 78 pictures studied.

Duxbury, Thomas C.↗
NASA NTRS1988

A search for optical millisecond pulsars in globular clusters

A search for millisecond optical pulsars in several bright, compact globular clusters was conducted. The sample included M28, and the X-ray clusters 47 Tuc, NGC 6441, NGC 6624, M22, and M15. The globular cluster M28 contains the recently discovered 327 Hz radio pulsar. Upper limits of 4 sigma to pulsed emission of (1-20) solar luminosities were found for the globular clusters tested, and 0.3 solar luminosity for the M28 pulsar for frequencies up to 500 Hz.

Middleditch, J. H.↗
NASA NTRS1989

A search for a dynamical attractor in Cygnus X-1

A method used for searching for low-dimensional attractors in fluctuating signals is applied to the aperiodicity observed in Cyg X-1. The analysis technique for determining the dimension of an attractor given its light curve, and the practical limitations in applying the technique, are described. The requirement of large amounts of low-noise data is found to be very important in using the technique. No low-dimensional attractor is found for the set of Cyg X-1 data used, but evidence of an attractor with large dimension may be present.

Lochner, James C.↗
NASA NTRS1989

A search for gamma rays of 1.5-20.0 MeV from Centaurus A

A search for a gamma-ray continuum and lines from Centaurus A is reported. No measurable gamma rays are found in the 1.5-20.0 MeV and 3 sigma upper limits are reported for various energies which are about a factor of two lower than the results reported by von Ballmoos et al. (1987). These upper limits, along with those of SAS 2 and COS B, suggest that the energy distribution turns over in the energy range of 500 keV to a few MeV. A high source temperature of 5 MeV or synchrotron self-Compton models for producing an excess of gamma rays of a few MeV do not appear necessary.

O'Neill, Terrence↗
NASA NTRS1989

Search for water in Comet P/Halley at 380 GHz

A search for the 4(14)-3(21) orthorotational transition of H2O near 380 GHz was conducted in the coma of Comet P/Halley on May 6, 1986 using a heterodyne receiver and a high resolution spectrometer on the NASA Kuiper Airborne Observatory (KAO). A measured upper limit flux density in a 2 MHz bandwidh was obtained. Model calculations, including both collisions and infrared vibrational excitation by the solar radiation flux, show that this upper limit corresponds to an upper limit on the water production rate of 1.5 x 10 to the 30th water molecules per second for an isothermal coma at 200 K and 1.5 x 10 to the 31st/s for a more realistic model of the coma.

Gulkis, S.↗
NASA NTRS1989

A search for K I in absorption in Comet Giacobini-Zinner

Spectra through the coma of P/Giacobini-Zinner toward the star SAO 035030 have been obtained during a close apulse. K I is searched for, and a 3-sigma upper limit of 3 x 10 to the 10th/cu cm at a distance of about 1500 km from the nucleus is found. This corresponds to a column abundance for Na I of less than 2 x 10 to the 11th/sq cm, assuming a solar abundance ratio for Na/K. The observations are not yet sufficiently sensitive to constrain either Na or K abundances, but a case is made from these data that such observations are feasible for the brighter periodic comets.

Schempp, W. V.↗
NASA NTRS1989

A search for quasi-periodic oscillations in 4U/MXB 1735-44

A search for quasi-periodic oscillations (QPOs) in 4U/MXB 1735-44 was performed using Exosat observations during which the source was in a horizontal branch of the spectral hardness-intensity diagram for about 8 hr and in a normal branch type of behavior for about 46 hr. No QPOs or low-frequency noise was found in the horizontal branch state. It is suggested that this absence is due to either low luminosity or the fact that the companion in 1735-44 is a main-sequence star.

Penninx, Wim↗
NASA NTRS1989

Search for Doppler-shifted gamma-ray emission from SS 433 using the SMM spectrometer

Data accumulated from 1980 to 1983 with the Gamma Ray Spectrometer aboard NASA's Solar Maximum Mission (SMM) satellite were searched for evidence of red and blue Doppler-shifted 1.37 MeV Mg-24 nuclear lines from SS 433. The SMM data base covers 270 days when SS 433 was in the field of view and includes periods of radio flaring and quiescence. No evidence was found for Doppler-shifted line emission in any of the spectra. The range of 3-sigma upper limits for individual 9 day integration periods was 0.0008-0.0023 photons/sq cm per sec for the blue beam, encompassing the reported about 1.5 MeV line, and 0.0008-0.002 photons/sq cm per sec for the red beam, encompassing the reported about 1.2 MeV line; the average 3-sigma upper limit in each beam for shifted about 1.37 MeV lines is 0.0015 photons/sq cm per sec for single 9 day integrations. The 3-sigma upper limit on 1.37 MeV gamma-ray emission over 23 9-day integration intervals for the red beam and 28 intervals for the blue beam is 0.0002 photons/sq cm per sec. These new limits from SMM can be reconciled with the HEAO 3 results only if SS 433 emits gamma radiation at or above the SMM sensitivity limit on rare occasions due to variable physical conditions in the system.

Geldzahler, B. J.↗
NASA NTRS1989

A search for p-mode oscillations of Jupiter - Serendipitous observations of nonacoustic thermal wave structure

Frequencies for the p-mode oscillations of Jupiter have been determined, and infrared brightness temperature fluctuations are used to search for the modes. Measurements of the infrared intensity of the Jovian disk were obtained in a broad bandwidth using a 20-element linear array. No p-mode oscillations were observed at the 0.07-K level in the 8-13-micron brightness temperature. The results suggest that Jovian p modes are not likely to have observable amplitudes. A prominent nonacoustic wave-like structure in the 8-13-micron brightness temperature is found both at 20 deg N and at the equator.

Deming, Drake↗
NASA NTRS1989

Stable carbon isotope fractionation in the search for life on early Mars

The utility of measurements of C-13/C-12 ratios in organic vs inorganic deposits for searching for signs of life on early Mars is considered. It is suggested that three assumptions are necessary. First, if there was life on Mars, it caused the fractionation of carbon isotopes in analogy with past biological activity on earth. Second, the fractionation would be detectable. Third, if a fractionation would be observed, there exist no abiotic explanations for the observed fractionation pattern.

Rothschild, L. J.↗
NASA NTRS1989

The space microwave interferometer and the search for cosmic background gravitational wave radiation

Present and planned investigations which use interplanetary spacecraft for gravitational wave searches are severely limited in their detection capability. This limitation has to do both with the Earth-based tracking procedures used and with the configuration of the experiments themselves. It is suggested that a much improved experiment can now be made using a multiarm interferometer designed with current operating elements. An important source of gravitational wave radiation, the cosmic background, may well be within reach of detection with these procedures. It is proposed to make a number of experimental steps that can now be carried out using TDRSS spacecraft and would conclude in the establishment of an operating multiarm microwave interferometer. This interferometer is projected to have a sensitivity to cosmic background gravitational wave radiation with an energy of less than 10(exp -4) cosmic closure density and to periodic waves generating spatial strain approaching 10(exp -19) in the range 0.1 to 0.001 Hz.

Anderson, Allen Joel↗
NASA NTRS1989

A search for iron features in the EXOSAT spectral survey sources

The results of the search for iron features performed on 40 of the 48 EXOSAT spectral survey sources are discussed. In thrirteen of the sources the spectral fit was improved by the inclusion of an iron emission line at approximately 6.5 keV. In three of these, an ionized absorption edge improved the spectral fit. In one source, the spectral fit was improved by the addition of a cold iron absorption edge at approximately 7.1 keV. Line equivalent widths are not well determined. A statistical analysis of the line fits suggest an inverse correlation between line equivalent width and intrinsic source luminosity. Comparison of the host galaxy axial ratio with the line equivalent width suggests that larger equivalent widths occur in sources with more nearly face on host galaxies.

Leighly, K. M.↗
NASA NTRS1990

Search for interstellar methane

Researchers searched for interstellar methane in the spectra of infrared sources embedded in molecular clouds. New observations of several lines of the P and R branches of the nu 3 band of CH4 near 3.3 microns give column densities in the range N less than 1(-2) times 10 to the minus 16th power cm(-2). Resulting abundance ratios are (CH4)/(CO) less than 3.3 times 10 to the minus 2nd power toward GL961 in NGC 2244 and less than 2.4 times 10 to the minus 3rd power toward GL989 in the NGC 2264 molecular cloud. The limits, and those determined in earlier observations of BN in Orion and GL490, suggest that there is little methane in molecular clouds. The result agrees with predictions of chemical models. Exceptions could occur in clouds where oxygen may be depleted, for example by H2O freezing on grains. The present observations probably did not sample such regions.

Knacke, R. F.↗