Engineering topics

Lutz, Barry L.

Publications and source records attributed to Lutz, Barry L..

13 records

NASA NTRS1994

Pre- and postperihelon abundances of gas and dust in comet Halley

Photometrically calibrated spectra of comet P/Halley (1986 III) were recorded between 1985 September 12-1986 June 10 using the Ohio State University Image Dissector Scanner on the Perkins 72 inch telescope at the Lowell Observatory. Column densities of CN, C3, CH, C2, and NH2 were calculated from measured fluxes in these spectra, and molecular scale lengths were deduced from the radial distribution of CN, C3, C2, and NH2. Production rates were computed using the new scale lengths and a Haser model analysis. Continuum emission at 4260 A was used to derive gas-to-dust ratios. The data indicate than comet Halley was approximately 2-5 times more abundant in gas and dust at postperihelion than preperihelion. On 1986 June 8 we observed the onset of a cometary ourburst which appeared very strong in dust production. The gas-to-dust ratios appeared to be subject to changes as a result of short-term outbursts but otherwise did not exhibit any systematic dependence on heliocentric distance. Reflectivity gradients of the continuum were also measured from the spectra. While most of the continua were red, blue continua were also observed which may be correlated with dust outbursts.

Womack, Maria↗

NASA NTRS1993

Ion abundances and implications for photochemistry in Comets Halley (1986 III) and Bradfield (1987 XXIX)

The Ohio State University Image Dissector Scanner on the Perkins 1.8-m telescope at the Lowell Observatory was used to record spectra of the plasma tails of Comets P/Halley (1986 III) and P/Bradfield (1987 XXIX, also 1987s). The ionic species CO(+), N2(+), CH(+), and H2O(+) were identified in these spectra, and column densities for them were calculated from measured fluxes. The observed N2(+)/H2O(+) ratios are at least an order of magnitude lower and the observed CH(+)/H2O(+) ratios are a factor of 100 higher than theoretical results. The abundance ratio N2/CO was derived in the plasma tail of Bradfield from N2(+) and CO(+) data, and found to be an order of magnitude higher than a value measured in Halley. The relative ion abundances of CH(+), N2(+), CO(+), and H2O(+) in Halley are consistent with in situ measurements obtained from the Giotto spacecraft.

Lutz, Barry L.↗

NASA NTRS1991

Outer planet studies

The focus is on observational studies of the composition, structure, and variability of planetary, satellite, and cometary atmospheres. The techniques used include spectroscopy, spectrophotometry, and photometric imaging in the spectral region from 3000 A to 5 microns. In addition to carrying out basic research into the origin, evolution, and current state of the solar system, these studies provide ground-truth support for observations of the solar system by NASA's missions, including the Voyager and Galileo Spacecraft, the Hubble Space Telescope, and the proposed Comet Rendezvous Asteroid Flyby (CRAF)-Cassini Mission.

Lutz, Barry L.↗

NASA NTRS1991

Deuterium on Venus: Observations from Earth

In view of the importance of the deuterium-to-hydrogen ratio in understanding the evolutionary scenario of planetary atmospheres and its relationship to understanding the evolution of our own Earth, we undertook a series of observations designed to resolve previous observational conflicts. We observed the dark side of Venus in the 2.3 micron spectral region in search of both H2O and HDO, which would provide us with the D/H ratio in Venus' atmosphere. We identified a large number of molecular lines in the region, belonging to both molecules, and, using synthetic spectral techniques, obtained mixing ratios of 34 plus or minus 10 ppm and 1.3 plus or minus 0.2 ppm for H2O and HDO, respectively. These mixing ratios yield a D/H ratio for Venus of D/H equals 1.9 plus or minus 0.6 times 10 (exp 12) and 120 plus or minus 40 times the telluric ratio. Although the detailed interpretation is difficult, our observations confirm that the Pioneer Venus Orbiter results and establish that indeed Venus had a period in its early history in which it was very wet, perhaps not unlike the early wet period that seems to have been present on Mars, and that, in contrast to Earth, lost much of its water over geologic time.

Lutz, Barry L.↗

NASA NTRS1991

Gas and dust production by Comet P/Halley (1910 II)

Selected long-slit spectrograms of Comet P/Halley, photographed during the postperihelion period between April 16 and June 3, 1910 have been quantitatively analyzed for comparison with the 1985/86 apparition. The Fe-V-Na spark spectrum was used to determine characteristic curves for these plates, and flux calibrations based on contemporaneous broad-band photometric measurements were applied. Haser model production rates for C2 and values Afp were computed for each of the nights selected and compared with the photometric observations obtained by Schleicher et al. (1987) during the comparable postperihelion period of the 1985/86 apparition. As found for the 1985/86 apparation, the gas and dust production in 1910 varied in phase, but the rates of production were higher than observed in 1986 by a small but statistically significant amount.

Howell, Ellen S.↗

NASA NTRS1990

Anomalous molecular abundances and the depletion of NH2 in Comet P/Giacobini-Zinner

Observations of the CN, C2, C3, and NH2 molecules in spectra of the Comet P/Giacobini-Zinner (P/G-Z) obtained during the 1985 apparition are presented. Haser-model production rates are derived, and it is found that Q(C2)/Q(CN) and Q(C3)/Q(CN) are low compared to those in normal comets. This indicates that C2 and C3 were underabundance in P/G-Z, in agreement with previous results. Q(NH2)/Q(CN) is determined for five comets for the first time to determine a 'normal' value for this ratio. The ratio for P/G-Z is low compared to the value for the ensemble, suggesting that NH2 was underabundant. For the five-comet sample, Q(C3)/Q(CN) exhibits a strong dependence with heliocentric distance, in contrast to Q(C2)/Q(CN) and Q(C3)/Q(CN). The dust-to-gas ratio is characterized by calculating the product of the dust-grain albedo, the filling factor, and the projected radius of the aperture and by computing the dust-to-gas mass ratio.

Beaver, John E.↗

NASA NTRS1990

Deuterium enrichment in the primitive ices of the protosolar nebula

On the basis of CH3D/CH4-ratio observations in the outer planets, the present effort to estimate the D/H ratio of the protosolar nebula's primitive ices arrives at two simple, yet effectively limiting models which constrain the degree of dilution undergone by deuterated volatiles through mixing with the initial hydrogen envelopes. These volatiles would have been contributed to planetary atmospheres by evaporated primordial ices. Ice D/H ratio model results of 0.0001 to 0.001 are compared with values for other potentially primitive material-containing bodies in the solar system, as well as with D/H ratio values from interstellar polyatomic molecules.

Lutz, Barry L.↗

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 NTRS1989

The 2.4 micron spectrum of Comet Halley - A search for H2 emission

A 2.4-micron spectrum of Comet Halley was obtained on April 1, 1986 with the UKIRT scanning Fabry-Perot-CVF equipped with an InSb detector. From the ratio of the measured flux from comet Halley to Zeta Her in the 8.8 x 10 to the -4th micron bandwidth, Comet Halley produced a detected flux of about 1.3 x 10 to the 5th photons/sec with a 1-sigma variance of 385 photons. The flux detected in the same spectral region by Maillard et al. (1986) agrees with the measurements reported here to within a factor of two. The data obtained are examined from the standpoint of the possible mechanisms of H2 production.

Smith, W. Hayden↗

NASA NTRS1988

Outer planet studies

The tasks of this grant include observational studies of the composition, structure and variability of planetary and satellite atmospheres, and the investigation of the problems associated with the fundamental calibration of these data. These studies are essential to providing ground-truth support for observations of the solar system by NASA's missions, including the VOYAGER and GALILEO spacecraft, the Hubble Space Telescope, and the proposed CRAF-Cassini mission. Complementary spectroscopic observations of comets were added in BY88 to support NASA's cometary program goals of the CRAF-Cassini mission. A very modest laboratory effort is also maintained to provide essential data needed by these observational programs, which may be otherwise unavailable. Many accomplishments during BY88 include: (1) discovery of HDO in the spectrum of Mars and the first determination of the D/H ratio in its atmosphere; (2) completion and publication of the study of CH3D in the spectrum of Titan and a determination of the mixing ratio in its atmosphere; and, completion of observations of CH3D in the spectrum of Neptune and a preliminary analysis of the CH3D/CH4 mixing ratio in its atmosphere.

Lutz, Barry L.↗

NASA NTRS1988

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 of HDO near 3.7 micrometers in the planet's spectrum. The ratio of deuterium to hydrogen is (9 + or - 4) x 10 to the -4th; the abundance of H2O was derived from lines near 1.1 micrometers. This ratio is enriched on Mars over the telluric value by a factor of 6 + or - 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.

Owen, Tobias↗

NASA NTRS1987

The solar system/interstellar medium connection - Gas phase abundances

Gas-phase abundances in the outer solar system are presented as diagnostics of the interstellar medium at the time of the solar system formation, some 4.55 billion years ago. Possible influences of the thermal and chemical histories of the primitive solar nebula and of the processes which led to the formation and evolution of the outer planets and comets on the elemental and molecular composition of the primordial matter are outlined. The major components of the atmospheres of the outer planets and of the comae of comets are identified, and the cosmogonical and cosmological implications are discussed.

Lutz, Barry L.↗

NASA NTRS1986

A possible deuterium anomaly: Implications of the CH3D/CH4 mixing ratios in the atmospheres of Jupiter, Saturn, and Uranus

Observations of CH3D in the atmospheres of the outer planets provide a test of the theory of deuterium fractionation equilibrium in the formation and evolution of these planets. Recent measurements of the CH3D/CH4 mixing ratios made for Saturn and Uranus are presented and intercompared with current values of Jupiter, illustrating large differences between the planets. Their implied D/H ratios are compared to D/H ratios derived from measurements of HD/H2; and, in the cases of Jupiter and Saturn, they may be incompatible. Implications of these comparisons are discussed in terms of the deuterium fractionation chemistry and possible enrichments of deuterium in the core ices of the planets.

Lutz, Barry L.↗