Engineering topics

Feierberg, M. A.

Publications and source records attributed to Feierberg, M. A..

14 records

NASA NTRS1985

The nature of C-class asteroids from 3-micron spectrophotometry

Narrowband spectrophotometry between 2.3 and 3.5 micrometers is presented for 14 main-belt C asteroids greater than 100 km in diameter. Absorption features at 3 micrometers due to water of hydration are present in the spectra of nine of the asteroids, with intensities ranging from 6 to 23 percent. The other five asteroids have no such absorption greater than 2 percent in intensity. The present C-asteroid population may be fragments of larger parent bodies with anhydrous C3-like cores and hydrated C1I- or C2M-like mantles.

Feierberg, M. A.↗

NASA NTRS1985

2.7- to 4.1-micron spectrophotometry of icy satellites of Saturn and Jupiter

Spectrophotometry is presented in the 2.7-4.1 micrometer spectral region for icy satellites of Saturn (Tethys, Dione, Rhea, Iapetus and Hyperion) and Jupiter (Europa, Ganymede and Callisto). The 3.6-micrometer reflectance peak characteristic of fine-grained water ice is observed prominently on the satellites of Saturn, faintly on the leading side of Europa, and not at all on Ganymede, Callisto or the dark side of Iapetus. The spectral reflectances of these icy satellites may be affected by their equilibrium surface temperatures and magnetospheric effects.

Lebofsky, L. A.↗

NASA NTRS1984

8- to 13-micron spectrophotometry of Comet IRAS-Araki-Alcock

Spectrophotometry between 8.0 and 13.0 microns at 2 percent spectral resolution is presented for areas in and near the nuclear condensation of Comet IRAS-Araki-Alcock (1983d) on May 11 and 12, 1983. All the spectra can be fit very well by blackbody curves, and no 10-micron silicate emissions are seen. The temperature structure of the coma suggests the presence of small (radii less than 5 microns) dust particles within 150 km of the nucleus and larger ones further out. The change in the spatial distribution of the infrared flux between the two nights suggests that an outburst may have occurred sometime on May 11.

Feierberg, M. A.↗

NASA NTRS1983

Detection of silicate emission features in the 8- to 13-micron spectra of main belt asteroids

A presentation is given of 8.0-13.0 micron spectra (Delta lambda/lambda = 0.02-0.03) for six main belt asteroids, which range from 58 to 220 km in diameter and sample the five principal taxonomic classes (C, S, M, R and E). Narrow, well-defined silicate emission features are present on two of the asteroids, the C-type 19 Fortuna and the M-type 21 Lutetia. No comparable emission features are observed on the S-types 11 Parthenope and 14 Irene, the R-type 349 Dembowska or the E-type 64 Angelina.

Feierberg, M. A.↗

NASA NTRS1983

The composition of asteroid 2 Pallas and its relation to primitive meteorites

High resolution spectroscopic observations of asteroid 2 Pallas from 1.7-3.5 microns are reported. These data are combined with previous measurements from 0.4-1.7 microns to interpret Pallas' surface mineralogy. Evidence is found for low-Fe(2+) hydrated silicates, opaque components, and low Fe(2+) anhydrous silicates. This assemblage is very similar to carbonaceous chondrite matrix material such as is found in type CI and CM meteorites, but it has been subjected to substantial aqueous alteration and there is a major extraneous anhydrous silicate component. This composition is compared to that of asteroid 1 Ceres. Although there are substantial differences in their broad band spectral reflectances it appears that both asteroids are genetically related to know carbonaceous chondrites.

Larson, H. P.↗

NASA NTRS1983

Intensity and extinction irregularities in the H2 emission from Orion

Fourteen lines of the v = 1-0 and v = 2-1 2 micron H2 quadrupole spectrum were measured in a series of ground-based spectroscopic observations of four locations within the Orion molecular cloud-H2 emission complex. Beam sizes of 7 and 10 arcsec were used, with a resolution of 1.8/cm. The results indicate that there are differences in the extinction between regions of as much as 20 mag. In particular there appears to be a ridge of material near the object IRS 2 (= IRc 9), a previously suggested source of activity. The 2-1 S (3) line intensity is substantially stronger at Peak 2 than the present models predict, and this observation is the first indication that there may be a non-Boltzmann distribution within the vibrational levels of shock-excited H2. A detection of the 1-0 Q (6) line is also reported, a feature which was previously absent in spectra of the Orion cloud.

Smith, H. A.↗

NASA NTRS1982

Spectroscopic evidence for undifferentiated S-type asteroids

The small solar system bodies broadly defined as asteroids have been considered the parent bodies for most or all meteorites. This association requires that the compositional differences between the various classes of meteorites be convincingly related to the observed compositions of asteroids. An investigation has been conducted regarding the compositional relationship between S-type asteroids and the common types of differentiated and undifferentiated meteorites. It is found that spectroscopic data for S-type asteroids are consistent with a simple, undifferentiated model and with certain variations of a differentiated model. However, the differentiated models for S-type asteroids are not supported by meteoritic evidence. It appears, therefore, that most S-type asteroids are undifferentiated bodies, similar to ordinary chondrites in composition.

Feierberg, M. A.↗

NASA NTRS1982

Infrared observations of the dark side of Iapetus

J, H, K, L and L-prime broadband and 2.8-3.8 micron narrowband photometric observations have been made of the dark side of Iapetus with circularly variable filter techniques. A 3-micron absorption feature is found which is too deep to be a residual water frost feature from the bright material around the poles. In light of laboratory simulations showing that the dark material must have a strong 3-cm absorption, it is suggested that the material may be a hydrated silicate mixed with a small amount of water frost.

Lebofsky, L. A.↗

NASA NTRS1981

The 1.7- to 4.2-micron spectrum of asteroid 1 Ceres - Evidence for structural water in clay minerals

A high-resolution Fourier spectrum (1.7-3.5 microns) and medium-resolution spectrophotometry (2.7-4.2 microns) were obtained for Asteroid 1 Ceres. The presence of the 3-micron absorption feature due to water of hydration was confirmed. The 3-micron feature is compared with the 3-micron bands due to water of hydration in clays and salts. It is concluded that the spectrum of Ceres shows a strong absorption at 2.7-2.8 microns due to structural OH groups in clay minerals. The dominant minerals on the surface of Ceres are therefore hydrated clay minerals structurally similar to terrestrial montmorillonites. There is also a narrow absorption feature at 3.1 microns which is attributable to a very small amount of water ice on Ceres. This is the first evidence for ice on the surface of an asteroid.

Lebofsky, L. A.↗

NASA NTRS1981

Spectroscopic evidence for aqueous alteration products on the surfaces of low-albedo asteroids

The spectral reflectances of primary components of the carbonaceous chondrite matrix materials (CCMM) and their secondary alteration products are compared with new observations of low-albedo asteroids. It is shown that the spectral differences between C-type asteroids and carbonaceous chondrites are consistent with differing degrees of aqueous alteration of CCMM.

Feierberg, M. A.↗

NASA NTRS1980

The meteorite-asteroid connection - The infrared spectra of eucrites, shergottites, and Vesta

Infrared reflectance spectra have been obtained for the meteorites Shergotty and Allan Hills (ALHA) 77005, a unique achondrite apparently related to the shergottites. Comparisons with the reflectance spectra of eucrites and asteroid 4 Vesta indicate that the surface of Vesta is covered with eucrite-like basalts and that, if shergottite-like basalts are present on the surface of Vesta, they must be a minor rock type. The paradox that both the eucrite and shergottite parent bodies should presently exist is examined. The preferred solution is that both eucrites and shergottites are derived from Vesta, and that this asteroid is compositionally and isotopically heterogeneous; however, other possible solutions cannot be ruled out.

Feierberg, M. A.↗

NASA NTRS1980

Spectroscopic evidence for two achondrite parent bodies - Asteroids 349 Dembowska and 4 Vesta

A Fourier spectrometer was used to obtain IR spectra of asteroids 349 Dembowska and 4 Vesta. The spectrum of Dembowska shows olivine and pyroxene with an olivine/pyroxene abundance ratio greater than 2, and possibly as high as 10. This is probably an unsampled achondritic composition, similar to the unique achondrite ALHA 77005. Dembowska's mineralogy therefore appears related to the achondrites; pyroxene and plagioclase feldspar are seen, with a pyroxene/feldspar abundance ratio between 1.5 and 2.0. Time-resolved observations over one-half of the rotation period indicate compositional homogeneity; both 349 Dembowska and 4 Vesta can be considered as candidates for the parent bodies of igneous meteorites.

Feierberg, M. A.↗

NASA NTRS1979

Remote spectroscopic identification of carbonaceous chondrite mineralogies Applications to Ceres and Pallas

High-resolution spectroscopic observations of asteroids Ceres and Pallas have been obtained in the 1.0- to 2.6-micron region. Combined with previous spectral measurements at other wavelengths, this work presents the broadband spectral reflectances of these asteroids over the 0.4- to 3.6-micron region. This extended coverage permits new analyses of the surface mineralogies of these objects. Using laboratory comparison spectra of meteorites and mixtures of terrestrial minerals, the surfaces of Ceres and Pallas are consistent with mixtures of opaques and hydrated silicates, such as are found in types C1 and C2 meteorites. This research emphasizes the importance of the 3-micron spectral region for studying by remote methods the relationship of carbonaceous chondrite mineralogies to asteroid surfaces.

Larson, H. P.↗

NASA NTRS1976

Multispectral mapping of the lunar surface using ground-based telescopes

Images of the lunar surface were obtained at several wavelengths using a silicon vidicon imaging system and ground-based telescopes. These images were recorded and processed in digital form so that quantitative information was preserved. The photometric precision of the images is shown to be better than 1%. Ratio images calculated by dividing images obtained at two wavelengths (0.40/0.56 and 0.95/0.56 microns) are presented for about 50% of the lunar frontside. Spatial resolution is about 2 km at the subearth point. A complex of distinct units is evident in the images. Earlier work with the reflectance spectrum of lunar materials indicates that, for the most part, these units are compositionally distinct.

Mccord, T. B.↗