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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Flora and threatened and endangered plants of John F. Kennedy Space Center, Florida

The vascular flora of the Kennedy Space Center (KSC) area was first studied in the 1970's. Nomenclatural and taxonomic changes as well as additional collections required revision of this list. The revised list includes 1045 taxa of which 850 are native and 195 are introduced. This appears to be a substantial proportion of the regional flora. Forty six taxa are endemic or nearly endemic to Florida, a level of endemism that appears high for the east coast of central Florida. Seventy three taxa (69 native) are listed as threatened, endangered, or of special concern on Federal or state lists. Taxa of special concern occur in all major habitats, but many are restricted to hammocks and hardwood swamps that constitute a minor proportion of the terrestrial vegetation. For some of these taxa, populations on KSC appear to be important for their regional and global survival. The bryophyte flora of the KSC area include 23 mosses and 20 liverworts and hornworts. The lichen flora is currently unknown.

Schmalzer, Paul A.↗
NASA NTRS1989

Asteroid lightcurve observations from 1979-1981

An account is given of the results of photometric light curve observations in the V band for asteroids, yielding estimates of the mean and maximum reduced magnitudes for each object. On the basis of fits of the H-G magnitude relation for 33 objects, the mean values of the slope parameter are examined for different taxonomic classes; these values are then applied to the analysis of less complete data sets. While in the case of the moderate albedo S and M class asteroids the H-G relation appears to fit the available data, the relation for dark asteroids appears to predict more of an opposition than is characteristically present.

Harris, A. W.↗
NASA NTRS1989

Phase relations of high albedo asteroids - The unusual opposition brightening of 44 Nysa and 64 Angelina

The present photoelectric lightcurve observations of 44 Nysa at one aspect, and 64 Angelina at both polar aspects, indicate the presence of an opposition spike or brightening of approximately 0.25 mag within several deg of zero-phase angle. Since the three curves are identical within the bounds of observational scatter, the opposition spike cannot be judged anomalous within the asteroid taxonomic class E. The general similarity of the observed phase curves to those of the Uranian satellites and the rings of Saturn supports the status of the spike as an ordinary property of moderate-to-high albedo atmosphereless surfaces.

Harris, A. W.↗
NASA NTRS1990

2060 Chiron - Colorimetry and cometary behavior

Ambiguities concerning the fit of the 2060 Chiron's visible spectrum to its IR spectrum have been resolved by resort to VRIJHK colorimetry obtained in 1988, which also confirms the neutrality of Chiron's taxonomic class C spectrum and indicates that Chiron has anomalously brightened since 1980-1983. This brightening, and one reported in 1978, are consistent with the hypothesis that Chiron sporadically undergoes weak cometary outbursts similar to those of comet P/Schwassmann-Wachmann 1; Chiron is further speculated to be an ice-rich object darkened by C-class carbonaceous soil, and may have been scattered from the Oort cloud in recent solar system history.

Hartmann, William K.↗
NASA NTRS1989

Asteroid taxonomy

The spectral reflectivity of asteroid surfaces over the wavelength range of 0.3 to 1.1 micron can be used to classify these objects into several broad groups with similar spectral characteristics. The three most recently developed taxonomies group the asteroids into 9, 11, or 14 different clases, depending on the technique used to perform the analysis. The distribution of the taxonomic classes shows that darker and redder objects become more dominant at larger heliocentric distances, while the rare asteroid types are found more frequently among the small objects of the planet-crossing population.

Tholen, David J.↗
NASA NTRS1989

Asteroids - The big picture

An attempt is made to construct a simple model of the evolution of the asteroid belt from the data available about the individual asteroids. Data on the meaning of taxonomic types, the stratigraphy of the asteroid belt, the compositional meaning of Tholen space, collisional and dynamical history, and asteroid shapes are reviewed. Two main paradoxes concerning asteroids, called the ordinary chondrite mystery and the olivine problems, are briefly described. Finally, the tentative model is presented, showing how it takes into account condensation locations, heating, collisional evolution, and delivery of asteroids to earth.

Bell, Jeffrey F.↗
NASA NTRS1989

Introduction to the Asteroids II data base

This paper describes the Asteroids II data base, which is a compilation of asteroid data published, or in press, as of March 1988 with some updates in early 1989. The Asteroids II machine-readable data base includes asteroid names and discovery circumstances; proper elements and family identifications; asteroid light-curve parameters; asteroid pole determinations; taxonomic classes; and absolute magnitudes and slope parameters, UBV colors, albedos, and diameters.

Tedesco, Edward F.↗
NASA NTRS1990

Chemical characterization of a unique chondrite - Allan Hills 85085

Allan Hills 85085 is a new and very important addition to the growing list of unique carbonaceous chondrites because of its unique chemical and mineralogical properties. This chemical study provides more precise data on the major, minor, and trace element characteristics of ALH85085. ALH85085 has compositional, petrological, and isotopic affinities to AL Rais and Renazzo, and to Bencubbin-Weatherford. The similarities to Al Rais and Renazzo suggest similar formation locations and thermal processing, possibly in the vicinity of CI chondrites. Petrologic, compositional and isotopic studies indicate that the components that control the abundance of the various refractory and volatile elements were not allowed to equilibrate with the nebula as conditions changed, explaining the inconsistencies in the classification of these meteorites using known taxonomic parameters.

Gosselin, David C.↗
NASA NTRS1990

The fossil record of evolution: Data on diversification and extinction

The two principle efforts include: (1) a compilation of a synoptic, mesoscale data base on times of origination and extinction of animal genera in the oceans over the last 600 million years of geologic time; and (2) an analysis of statistical patterns in these data that relate to the diversification of complex life and to the occurrence of mass extinctions, especially those that might be associated with extraterrestrial phenomena. The data base is unique in its taxonomic scope and detail and in its temporal resolution. It is a valuable resource for investigating evolutionary expansions and extinctions of complex life.

Sepkoski, J. John, Jr.↗
NASA NTRS1991

Near-infrared reflectance spectra-applications to problems in asteroid-meteorite relationships

Near-infrared spectral reflectance data were collected at the Infrared Telescope Facility (IRTF) at Mauna Kea Observatories in 1985 and 1986 for the purpose of searching the region near the 3:1 Kirkwood gap for asteroids with the spectral signatures of ordinary chondrite parent bodies. Twelve reflectance spectra are observed. The presence of ordinary chondrite parent bodies among this specific set of observed asteroids is not obvious, though the sample is biased towards the larger asteroids in the region due to limitations imposed by detector sensitivity. The data set, which was acquired with the same instrumentation used for the 52-color asteroid survey (Bell et al., 1987), also presents some additional findings. The range of spectral characteristics that exist among asteroids of the same taxonomic type is noted. Conclusions based on the findings are discussed.

Mcfadden, Lucy A.↗
NASA NTRS1991

The 15 years of comet photometry: A comparative analysis of 80 comets

In 1976, a program of narrowband photometry of comets was initiated that has encompassed well over 400 nights of observations. To date, the program has provided detailed information on 80 comets, 11 of which were observed during multiple apparitions. The filters (initially isolating CN, C2, and continuum and later including C3, OH, and NH) as well as the detectors used for the observations were changed over time, and the parameters adopted in the reduction and modeling of the data have likewise evolved. Accordingly, we have re-reduced the entire database and have derived production rates using current values for scalelengths and fluorescence efficiencies. Having completed this task, the results for different comets can now be meaningfully compared. The general characteristics that are discussed include ranges in composition (molecular production rate ratios) and dustiness (gas production compared with Af(rho)). Additionally an analysis of trends on how the production rates vary with heliocentric distance and on pre- and post-perihelion asymmetries in the production rates of individual comets. Possible taxonomic groupings are also described.

Osip, David J.↗
NASA NTRS1991

A census of the asteroid belt

Observations obtained by the Infrared Astronomical Satellite (IRAS) during its ten month mission in 1983 were originally processed by the Asteroid Data Analysis System (ADAS) to search for 3453 asteroids with known orbital elements as of September 1985. A total of 1811 had one or more observations of sufficient reliability to be accepted. These results were released in October 1986. Recently IRAS data were reprocessed to increase both the number of recognized asteroid observations and their reliability. As input 7311 asteroids were used with known orbital elements as of December 1990. This processor is referred to as the IRAS Minor Planet Survey (IMPS). As of April 1991 approximately 3000 asteroids had been identified with one or more acceptable observations. These results were used to derive the total number of asteroids with diameters greater than 1 km. In addition to being an interesting piece of information in itself these size-frequency distributions produce bias-correction factors which, for example, will be used in investigations of the physical properties of asteroid dynamical families and to estimate the distribution of the taxonomic classes as a function of heliocentric distance.

Tedesco, E. F.↗
NASA NTRS1991

Asteroid/meteorite streams

The independent discovery of the same three streams (named alpha, beta, and gamma) among 139 Earth approaching asteroids and among 89 meteorite producing fireballs presents the possibility of matching specific meteorites to specific asteroids, or at least to asteroids in the same stream and, therefore, presumably of the same composition. Although perhaps of limited practical value, the three meteorites with known orbits are all ordinary chondrites. To identify, in general, the taxonomic type of the parent asteroid, however, would be of great scientific interest since these most abundant meteorite types cannot be unambiguously spectrally matched to an asteroid type. The H5 Pribram meteorite and asteroid 4486 (unclassified) are not part of a stream, but travel in fairly similar orbits. The LL5 Innisfree meteorite is orbitally similar to asteroid 1989DA (unclassified), and both are members of a fourth stream (delta) defined by five meteorite-dropping fireballs and this one asteroid. The H5 Lost City meteorite is orbitally similar to 1980AA (S type), which is a member of stream gamma defined by four asteroids and four fireballs. Another asteroid in this stream is classified as an S type, another is QU, and the fourth is unclassified. This stream suggests that ordinary chondrites should be associated with S (and/or Q) asteroids. Two of the known four V type asteroids belong to another stream, beta, defined by five asteroids and four meteorite-dropping (but unrecovered) fireballs, making it the most probable source of the eucrites. The final stream, alpha, defined by five asteroids and three fireballs is of unknown composition since no meteorites have been recovered and only one asteroid has an ambiguous classification of QRS. If this stream, or any other as yet undiscovered ones, were found to be composed of a more practical material (e.g., water or metalrich), then recovery of the associated meteorites would provide an opportunity for in-hand analysis of a potential near-Earth resource.

Drummond, J.↗
NASA NTRS1991

Will Galileo resolve the S-asteroid controversy?

The longest running argument in asteroid science concerns mineral composition and meteoritic association of the asteroids assigned to taxonomic type S. The approaching flyby of the S-type asteroid Gaspra by the Galileo spacecraft will drag an even larger section of the space science community into this argument. The basics of this problem are presented and discussed. The various proposed S asteroid compositions are presented and summarized in roughly the order in which they appeared.

Bell, Jeffrey F.↗
NASA NTRS1991

Visual and infrared studies of asteroids and the Pluto-Charon system

The strategy of the project was to: (1) analyze light curves of Pluto-Charon mutual eclipse event light curves to derive models of the Pluto-Charon system; (2) use these results in planning and reducing HST observations tentatively scheduled to be obtained in Aug. 1991 to determine Pluto-Charon mass ratio; and (3) obtain visual and IR photometry of selected asteroids to help determine their albedos, sizes, shapes, pole orientations, taxonomic classes, and phase functions.

Tedesco, Edward F.↗
NASA NTRS1991

Physical studies of small asteroids and cometary nuclei

Photoelectric and CCD photometry of small asteroids in the 0.5-25 km diameter range and cometary cores are discussed. It is to reconcile the observed physical properties of those bodies with models and laboratory experiments. As there is an inevitable spread between the laboratory scale and the real asteroid scale, the observations of smaller bodies offer us a natural laboratory to serve as an intermediate link between experimental sizes and real ones. Whenever possible, UBVWX color are obtained to define taxonomic classes.

Wisniewski, Wieslaw Z.↗
NASA NTRS1991

Angular momentum transfer in low velocity oblique impacts - Implications for asteroids

An experimental study has been conducted for the low-velocity oblique impact efficiency of angular momentum transfer, which is defined as that fraction of incident angular momentum that is transferred to the rotation of a target. The results obtained suggest that more energetic impacts are able to transfer angular momentum more efficiently. In the cases of ricochetted projectiles, the fraction of angular momentum carried off by the ejecta was noted to be less than 30 percent. It is suggested that, if asteroid spin rates are due to mutual noncatastrophic collisions and the taxonomic classes are indicative of bulk properties, the differences between corresponding spin rates will be smaller than expected from a consideration of relative strength and density alone.

Yanagisawa, Masahisa↗
NASA NTRS1992

Remote sensing of the biological dynamics of large-scale salt evaporation ponds

Optical properties of salt evaporation ponds associated with Exportadora de Sal, a salt production company in Baja California Sur, Mexico, were analyzed using a combination of spectroradiometer and extracted pigment data, and Landsat-5 Thematic Mapper imagery. The optical characteristics of each pond are determined by the biota, which consists of dense populations of algae and photosynthetic bacteria containing a wide variety of photosynthetic and photoprotective pigments. Analysis has shown that spectral and image data can differentiate between taxonomic groups of the microbiota, detect changes in population distributions, and reveal large-scale seasonal dynamics.

Richardson, Laurie L.↗