Acid dissolution experiments: carbonates and the 6.8-micrometer bands in interplanetary dust particles

A chemical dissolution experiment on an interplanetary dust particle (IDP) showed that carbonates, not acid-insoluble organic compounds, were responsible for virtually all the absorption at 6.8 micrometers seen in the infrared spectra of this particle. The IDP examined had an infrared spectrum characteristic of layer-lattice silicates and belongs to a class of IDP's whose spectra resemble those of protostellar objects like W33 A, which also exhibit a band at 6.8 micrometers.     

Interstellar polycyclic aromatic hydrocarbons and carbon in interplanetary dust particles and meteorites

Both interplanetary dust particles (IDP(s)) and meteorites may contain material that is similar to polycyclic aromatic hydrocarbons(PAH(s)). The Raman spectra of IDP(s) and meteorites show features that are similar in position and relative strength to interstellar infrared emission features that have been attributed to vibrational transitions in free, molecular-sized PAH(s). The Raman spectra of some IDP(s) also show red photoluminescence that is similar to the excess red emission seen in some astronomical objects and that has also been attributed to PAH(s) and hydrogenated amorphous carbon. Moreover, a part of the carbonaceous phase in IDP(s) and meteorites contains deuterium to hydrogen ratios that are greater than those for terrestrial samples. Deuterium enrichment is expected in small free PAH(s) that are exposed to ultraviolet radiation in the interstellar medium. Taken together, these observations suggest that some of the carbonaceous material in IDP(s) and meteorites may have been produced in circumstellar dust shells and only slightly modified in interstellar space.     

CH5+: the infrared spectrum observed

Protonated methane, CH5+, has unusual vibrational and rotational behavior because its three nonequivalent equilibrium structures have nearly identical energies and its five protons scramble freely. Although many theoretical papers have been published on the quantum mechanics of the system, a better understanding requires spectral data. A complex, high-resolution infrared spectrum of CH5+ corresponding to the C-H stretching band in the 3.4-micrometer region is reported. Although no detailed assignment of the individual lines was made, comparison with other carbocation spectra strongly suggests that the transitions are due to CH5+.     

Organic matter on asteroid 130 elektra

Infrared absorption spectra of a low-albedo water-rich asteroid appear to show a weak 3.4-micrometer carbon-hydrogen stretching mode band, which suggests the presence of hydrocarbons on asteroid 130 Elektra. The organic extract from the primitive carbonaceous chondritic Murchison meteorite shows similar spectral bands.     

Transparent, conductive carbon nanotube films

We describe a simple process for the fabrication of ultrathin, transparent, optically homogeneous, electrically conducting films of pure single-walled carbon nanotubes and the transfer of those films to various substrates. For equivalent sheet resistance, the films exhibit optical transmittance comparable to that of commercial indium tin oxide in the visible spectrum, but far superior transmittance in the technologically relevant 2- to 5-micrometer infrared spectral band. These characteristics indicate broad applicability of the films for electrical coupling in photonic devices. In an example application, the films are used to construct an electric field-activated optical modulator, which constitutes an optical analog to the nanotube-based field effect transistor.     

Spectroscopic identification of carbonate minerals in the martian dust

Thermal infrared spectra of the martian surface indicate the presence of small concentrations (approximately 2 to 5 weight %) of carbonates, specifically dominated by magnesite (MgCO3). The carbonates are widely distributed in the martian dust, and there is no indication of a concentrated source. The presence of small concentrations of carbonate minerals in the surface dust and in martian meteorites can sequester several bars of atmospheric carbon dioxide and may have been an important sink for a thicker carbon dioxide atmosphere in the martian past.     

The dust grains from 9P/Tempel 1 before and after the encounter with Deep Impact

Gemini-N observed the properties of dust ejected from the nucleus of comet 9P/Tempel 1 before and after its encounter with Deep Impact. Marked changes were seen in the 7.8- to 13-micrometer spectral energy distribution and derived grain properties of the inner coma. A strong, broad silicate feature dominated by emission from amorphous pyroxene, amorphous olivine, and magnesium-rich crystalline olivine had developed by 1 hour after impact. The ejected dust mass is congruent with 10(4) to 10(6) kilograms on the basis of our models. Twenty-six hours later the silicate feature had faded, leaving a smooth featureless spectrum, similar to that observed before the impact, suggesting that the impact did not produce a new active region releasing small particles on the nucleus.     

Spitzer spectral observations of the deep impact ejecta

Spitzer Space Telescope imaging spectrometer observations of comet 9P/Tempel 1 during the Deep Impact encounter returned detailed, highly structured, 5- to 35-micrometer spectra of the ejecta. Emission signatures due to amorphous and crystalline silicates, amorphous carbon, carbonates, phyllosilicates, polycyclic aromatic hydrocarbons, water gas and ice, and sulfides were found. Good agreement is seen between the ejecta spectra and the material emitted from comet C/1995 O1 (Hale-Bopp) and the circumstellar material around the young stellar object HD100546. The atomic abundance of the observed material is consistent with solar and C1 chondritic abundances, and the dust-to-gas ratio was determined to be greater than or equal to 1.3. The presence of the observed mix of materials requires efficient methods of annealing amorphous silicates and mixing of high- and low-temperature phases over large distances in the early protosolar nebula.     

Spectroscopic observations of Mercury's surface reflectance during MESSENGER's first Mercury flyby

During MESSENGER's first flyby of Mercury, the Mercury Atmospheric and Surface Composition Spectrometer made simultaneous mid-ultraviolet to near-infrared (wavelengths of 200 to 1300 nanometers) reflectance observations of the surface. An ultraviolet absorption (<280 nanometers) suggests that the ferrous oxide (Fe2+) content of silicates in average surface material is low (less than 2 to 3 weight percent). This result is supported by the lack of a detectable 1-micrometer Fe2+ absorption band in high-spatial-resolution spectra of mature surface materials as well as immature crater ejecta, which suggests that the ferrous iron content may be low both on the surface and at depth. Differences in absorption features and slope among the spectra are evidence for variations in composition and regolith maturation of Mercury's surface.     

An Interplanetary Dust Particle Linked Directly to Type CM Meteorites and an Asteroidal Origin

Tochilinite, an ordered mixed-layer mineral containing Mg, Al, Fe, Ni, S, and O, has been identified in an interplanetary dust particle (IDP). This mineral is found in only one other class of meteoritic materials, type CM carbonaceous chondrites. The presence of tochilinite in an IDP provides a direct petrogenetic link between a member of the layer-silicate subset of IDPs and a specific class of meteorites and thus establishes that some IDPs collected in the stratosphere have an asteroidal origin. The scarcity of this IDP type suggests that materials with CM mineralogy are not abundant among the dust-producing asteroids.     

Surface ices and the atmospheric composition of pluto

Observations of the 1.4- to 2.4-micrometer spectrum of Pluto reveal absorptions of carbon monoxide and nitrogen ices and confirm the presence of solid methane. Frozen nitrogen is more abundant than the other two ices by a factor of about 50; gaseous nitrogen must therefore be the major atmospheric constituent. The absence of carbon dioxide absorptions is one of several differences between the spectra of Pluto and Triton in this region. Both worlds carry information about the composition of the solar nebula and the processes by which icy planetesimals formed.     

Identification of complex aromatic molecules in individual interplanetary dust particles

Seventeen stratospherically collected particles-eight of which are classified as interplanetary dust particles (IDPs), seven of which are classified as probable terrestrial contaminants, and two of which have uncertain origins-were studied with a microprobe two-step laser mass spectrometer. Many polycyclic aromatic hydrocarbons(PAHs) and their alkylated derivatives were identified in two of the eight IDPs. The PAHs observed include a high-mass envelope not found in meteorites or terrestrial contaminants and prominent odd-mass peaks suggestive of nitrogen-containing functional groups attached to aromatic chromophores. In addition, the complexity of the IDP mass spectra has no precedence in previous studies of meteorite samples or their acid residues. Extensive checks were performed to demonstrate that the PAH signals are not caused by terrestrial contaminants.     

Near-infrared spectral results of asteroid Itokawa from the Hayabusa spacecraft

The near-infrared spectrometer on board the Japanese Hayabusa spacecraft found a variation of more than 10% in albedo and absorption band depth in the surface reflectance of asteroid 25143 Itokawa. Spectral shape over the 1-micrometer absorption band indicates that the surface of this body has an olivine-rich mineral assemblage potentially similar to that of LL5 or LL6 chondrites. Diversity in the physical condition of Itokawa's surface appears to be larger than for other S-type asteroids previously explored by spacecraft, such as 433 Eros.     

Initial results from the Mini-TES experiment in Gusev Crater from the Spirit Rover

The Miniature Thermal Emission Spectrometer (Mini-TES) on Spirit has studied the mineralogy and thermophysical properties at Gusev crater. Undisturbed soil spectra show evidence for minor carbonates and bound water. Rocks are olivinerich basalts with varying degrees of dust and other coatings. Dark-toned soils observed on disturbed surfaces may be derived from rocks and have derived mineralogy (+/-5 to 10%) of 45% pyroxene (20% Ca-rich pyroxene and 25% pigeonite), 40% sodic to intermediate plagioclase, and 15% olivine (forsterite 45% +/-5 to 10). Two spectrally distinct coatings are observed on rocks, a possible indicator of the interaction of water, rock, and airfall dust. Diurnal temperature data indicate particle sizes from 40 to 80 microm in hollows to approximately 0.5 to 3 mm in soils.     

Magnetic fields in the formation of sun-like stars

We report high-angular-resolution measurements of polarized dust emission toward the low-mass protostellar system NGC 1333 IRAS 4A. We show that in this system the observed magnetic field morphology is in agreement with the standard theoretical models of the formation of Sun-like stars in magnetized molecular clouds at scales of a few hundred astronomical units; gravity has overcome magnetic support, and the magnetic field traces a clear hourglass shape. The magnetic field is substantially more important than turbulence in the evolution of the system, and the initial misalignment of the magnetic and spin axes may have been important in the formation of the binary system.     

The Cometary and Interstellar Dust Analyzer at comet 81P/Wild 2

The CIDA (Cometary and Interstellar Dust Analyzer) instrument on the Stardust spacecraft is a time-of-flight mass spectrometer used to analyze ions formed when fast dust particles strike the instrument's target. In the spectra of 45 presumably interstellar particles, quinone derivates were identified as constituents in the organic component. The 29 spectra obtained during the flyby of Comet 81P/Wild 2 confirm the predominance of organic matter. In moving from interstellar to cometary dust, the organic material seems to lose most of its hydrogen and oxygen as water and carbon monoxide. These are now present in the comet as gas phases, whereas the dust is rich in nitrogen-containing species. No traces of amino acids were found. We detected sulfur ions in one spectrum, which suggests that sulfur species are important in cometary organics.     

Detection of a deep 3-microm absorption feature in the spectrum of Amalthea (JV)

Near-infrared spectra of Jupiter's small inner satellites Amalthea and Thebe are similar to those of D-type asteroids in the 0.8- to 2.5-micrometer wavelength range. A deep absorption feature is detected at 3 micrometers in the spectra of the trailing side of Amalthea, which is similar to that of the non-ice components of Callisto and can be attributed to hydrous minerals. These surface materials cannot be explained if the satellite formed at its present orbit by accreting from a circumjovian nebula. Amalthea and Thebe may be the remnants of Jupiter's inflowing building blocks that formed in the outer part or outside of the circumjovian nebula.     

Organics captured from comet 81P/Wild 2 by the Stardust spacecraft

Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.     

Atmospheric temperature: successful test of remote probing

The Nimbus III satellite carries the satellite infrared spectrometer (SIRS). It measures the radiance of the earth and the atmosphere in seven narrow spectral intervals in the 15-micrometer carbon dioxide band and in one interval of minimum absorption at 11.1 micrometers. Seven simultaneous equations are solved to obtain the vertical temperature profile; the eighth measurement is used to determine the boundary condition (cloud or surface temperature). Results agree with those obtained from conventional radiosondes.     

High-speed lightwave transmission in optical fibers

There has been considerable progress in the telecommunications technology based on the transmission of lightwaves through optical fibers. Systems experiments in the 1.55-micrometer band have now demonstrated the capability of transmitting at rates as high as 2 gigabits per second over fiber lengths exceeding 100 kilometers, without the use of repeaters to boost the signal. Elements of this progress are advances in the fabrication of low-loss single-mode fibers, in the spectral control of semiconductor junction lasers assuring single-frequency operation, and in high-speed detectors and receivers.