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NASA NTRS2015

Using Dust from Asteroids as Regolith Microsamples

More robust links need to be forged between meteorites and their parent bodies to understand the composition, diversity and distribution of the asteroids. A major link can be sample analysis of the parent body material and comparison with meteorite data. Dust is present around all airless bodies, generated by micrometeorite impact into their airless surfaces, which in turn lofts regolith particles into a "cloud" around the body. The composition, flux, and size distribution of dust particles can provide insight into the geologic evolution of airless bodies. For example, the Cassini Cosmic Dust Analyzer detected salts and minerals emitted by plumes at Enceladus, evidence for a subsurface ocean with a silicate seafloor. Dust analysis instruments may enable future missions to obtain elemental, isotopic and mineralogical composition of regolith particles without returning the samples to terrestrial laboratories.

dust↗
NASA NTRS1991

The dynamics of submicron-sized dust particles lost from Phobos

The dynamics of submicron-sized dielectric particles lost from the Martian moon Phobos are studied in connection with the possible detection of dust by the Phobos 2 spacecraft. The motion of these small dust grains is influenced not only by gravity but also by solar radiation pressure and electromagnetic forces. The plasma environment of Mars is described by applying a hybrid gasdynamic-cometary model. Some of the submicron-sized grains ejected at speeds on the order of a few tens meters per second can stay in orbit around Mars for several months forming a nonuniform and time-dependent dust halo.

Horanyi, M.↗
NASA NTRS2010

The Fourier-Kelvin Stellar Interferometer (FKSI): Infrared Detection and Characterization of Exozodiacal Dust to Super-Earths, A Progress Report

The Fourier-Kelvin Stellar Interferometer (FKSI) is a structurally connected infrared space interferometer with 0.5 m diameter telescopes on a 12.5 m baseline, and is passively cooled to approx.60K. The FKSI operates in the thermal infrared from 3-8 microns in a nulling (or starlight suppressing) mode for the detection and characterization of exoplanets, debris disks, extrasolar zodiacal dust levels. The FKSI will have the highest angular resolution of any infrared space instrument ever made with its nominal resolution of 40 mas at a 5 micron center wavelength. This resolution exceeds that of Spitzer by a factor of 38 and JWST by a factor of 5. The FKSI mission is conceived as a "probe class" or "mid-sized" strategic mission that utilizes technology advances from flagship projects like JWST, SIM, Spitzer, and the technology programs of TPF-I/Darwin. During the past year we began investigating an enhanced version of FKSI with 1-2 m diameter telescopes, passively cooled to 40K, on a 20-m baseline, with a sunshade giving a +/- 45 degree Field-of-Regard. This enhanced design is capable of detecting and characterizing the atmospheres of many 2 Earth-radius super-Earths and a few Earth-twins. We will report progress on the design of the enhanced mission concept and current status of the technologies needed for this mission.

Danchi, W.↗
NASA NTRS1994

Interplanetary dust particles collected from the stratosphere: Physical, chemical, and mineralogical properties and implications for their sources

The suggestion that significant quantities of interplanetary dust are produced by both main-belt asteroids and comets is based on the Infrared Astronomical Satellite (IRAS) detection of dust trails or bands associated with these objects. Gravitational focusing strongly biases all near-Earth collections of interplanetary dust in favor of particles with the lowest geocentric velocities, that is the dust from main-belt asteroids spiraling into the Sun under the influence of Poynting-Robertson radiation drag. The major dust bands in the main-belt appear to be associated with the catastrophic disruptions which produced the Eos, Themis and Koronis families of asteroids. If dust particles are produced in the catastrophic collision process, then Poynting-Robertson radiation drag is such an efficient transport mechanism from the main-belt to 1 AU that near-Earth collections of interplanetary dust should include, and perhaps be dominated by, this material. Interplanetary dust particles from 5 to 100 micrometers in diameter have been recovered from the stratosphere of the Earth by NASA sampling aircraft since the mid-1970s. The densities of a large fraction of these interplanetary dust particles are significantly lower than the densities of their constituent silicate mineral phases, indicating significant porosites. The majority of the particles are chemically and mineralogically similar to, but not identical to, the carbonaceous chondrite meteorites. Most stony interplanetary dust particles have carbon contents exceeding those of Allende, a carbonaceous chondrite meteorite having a low albedo. Higher albedo particles corresponding to S-type asteroids are underrepresented or absent from the stratospheric collections, and primitive carbonaceous particles seem to be overrepresented in the stratospheric collections compared to the fraction of main-belt asteroids classified as primitive. This suggests that much of the interplanetary dust may be generated by a stochastic process, probably preferentially sampling a few most recent collisional events.

Flynn, George J.↗
NASA NTRS2010

Laboratory Annealing Experiments Of Refractory Silicate Grain Analogs Using Differential Scanning Calorimetry

Exothermic reactions during the annealing of laboratory synthesized amorphous magnesium-bearing silicate particles used as grain analogs of cosmic dust were detected by differential scanning calorimetry (DSC) in air. With infrared spectroscopy and transmission electron microscopy, we show that cosmic dust could possibly undergo fusion to larger particles, with oxidation of magnesium silicide and crystallization of forsterite as exothermic reactions in the early solar system. The reactions begin at approximately 425, approximately 625, and approximately 1000 K, respectively, and the reaction energies (enthalpies) are at least 727, 4151, and 160.22 J per gram, respectively. During the crystallization of forsterite particles, the spectral evolution of the 10 micrometer feature from amorphous to crystalline was observed to begin at lower temperature than the crystallization temperature of 1003 K. During spectral evolution at lower temperature, nucleation and/or the formation of nanocrystallites of forsterite at the surface of the grain analogs was observed.

Kimura, Yuki↗
NASA NTRS2008

Spatially Resolved Imaging at 350 Micrometers of Cold Dust in Nearby Elliptical Galaxies

Continuum observations at 350 micrometers of seven nearby elliptical galaxies for which CO gas disks have recently been resolved with interferometry mapping are presented. These SHARC II mapping results provide the first clearly resolved far-infrared (FIR)-to-submillimeter continuum emission from cold dust (with temperatures 31 K is approximately greater than T approximately greater than 23 K) of any elliptical galaxy at a distance greater than 40 Mpc. The measured FIR excess shows that the most likely and dominant heating source of this dust is not dilute stellar radiation or cooling flows, but rather star formation that could have been triggered by an accretion or merger event and fueled by dust-rich material that has settled in a dense region cospatial with the central CO gas disks. The dust is detected even in two cluster ellipticals that are deficient in H (sub I), showing that, unlike H (sub I), cold dust and CO in ellipticals can survive in the presence of hot X-ray gas, even in galaxy clusters. No dust cooler than 20 K, either distributed outside the CO disks or cospatial with and heated by the entire dilute stellar optical galaxy (or very extended H (sub I)), is currently evident.

photometry↗
NASA NTRS1990

The probable dust formation episode around Rho Cassiopeiae

By comparing IRAS photometry with previous 10-micron data, it appears that dust formed in the circumstellar envelope around the supergiant G star, Rho Cas, sometime between 1973 and 1983. This dust formation may have been the consequence of the gas outflowing and cooling from the intense mass outburst of 1946. In 1983, the dust was detected at a temperature between 600 and 800 K at a distance between 10 to the 15th cm and 4 x 10 to the 15th cm from the star. While the dust-to-gas ratio in the circumstellar envelope may be as low as 0.00001 and thus much lower than in other mass-losing stars, the luminosity of Rho Cas is sufficiently large that radiation pressure on this dust might be dynamically important in helping to drive mass loss.

Jura, M.↗
NASA NTRS2010

A Combined Observational and Modeling Approach to Study Modern Dust Transport from the Patagonia Desert to East Antarctica

The understanding of present atmospheric transport processes from Southern Hemisphere (SH) landmasses to Antarctica can improve the interpretation of stratigraphic data in Antarctic ice cores. In addition, long range transport can deliver key nutrients normally not available to marine ecosystems in the Southern Ocean and may trigger or enhance primary productivity. However, there is a dearth of observational based studies of dust transport in the SH. This work aims to improve current understanding of dust transport in the SH by showing a characterization of two dust events originating in the Patagonia desert (south end of South America). The approach is based on a combined and complementary use of satellite retrievals (detectors MISR, MODIS, GLAS ,POLDER, OMI,), transport model simulation (HYSPLIT) and surface observations near the sources and aerosol measurements in Antarctica (Neumayer and Concordia sites). Satellite imagery and visibility observations confirm dust emission in a stretch of dry lakes along the coast of the Tierra del Fuego (TdF) island (approx.54deg S) and from the shores of the Colihue Huapi lake in Central Patagonia (approx.46deg S) in February 2005. Model simulations initialized by these observations reproduce the timing of an observed increase in dust concentration at the Concordia Station and some of the observed increases in atmospheric aerosol absorption (here used as a dust proxy) in the Neumayer station. The TdF sources were the largest contributors of dust at both sites. The transit times from TdF to the Neumayer and Concordia sites are 6-7 and 9-10 days respectively. Lidar observations and model outputs coincide in placing most of the dust cloud in the boundary layer and suggest significant de- position over the ocean immediately downwind. Boundary layer dust was detected as far as 1800 km from the source and approx.800 km north of the South Georgia Island over the central sub-Antarctic Atlantic Ocean. Although the analysis suggests the presence of dust at approx.1500 km SW of South Africa five days after, the limited capabilities of existing satellite platforms to differentiate between aerosol types do not permit a definitive conclusion. In addition, the model simulations show dust lifting to the free troposphere as it travels south but it could not be confirmed by the satellite observations due to cloudiness. This work demonstrates that complementary information from existing transport models, satellite and surface data can yield a consistent picture of the dust transport from the Patagonia desert to Antarctica. It also illustrates the limitation of using any of these approaches individually to characterize the transport of dust in a heavily cloudy area.

Gasso, S.↗
NASA NTRS2010

Holographic Vortex Coronagraph

A holographic vortex coronagraph (HVC) has been proposed as an improvement over conventional coronagraphs for use in high-contrast astronomical imaging for detecting planets, dust disks, and other broadband light scatterers in the vicinities of stars other than the Sun. Because such light scatterers are so faint relative to their parent stars, in order to be able to detect them, it is necessary to effect ultra-high-contrast (typically by a factor of the order of 1010) suppression of broadband light from the stars. Unfortunately, the performances of conventional coronagraphs are limited by low throughput, dispersion, and difficulty of satisfying challenging manufacturing requirements. The HVC concept offers the potential to overcome these limitations.

Palacios, David↗
NASA NTRS2018

Resolving Faint Structures in the Debris Disk Around TWA 7* Tentative Detections of an Outer Belt, a Spiral Arm, and a Dusty Cloud

Context. Debris disks are the intrinsic by-products of the star and planet formation processes. Most likely due to instrumental limitations and their natural faintness, little is known about debris disks around low mass stars, especially when it comes to spatially resolved observations. Aims. We present new VLT/SPHERE IRDIS dual-polarization imaging (DPI) observations in which we detect the dust ring around the M2 spectral type star TWA 7. Combined with additional angular differential imaging observations we aim at a fine characterization of the debris disk and setting constraints on the presence of low-mass planets. Methods. We modeled the SPHERE DPI observations and constrain the location of the small dust grains, as well as the spectral energy distribution of the debris disk, using the results inferred from the observations, and performed simple N-body simulations. Results. We find that the dust density distribution peaks at ~0.72′′ (25 au), with a very shallow outer power-law slope, and that the disk has an inclination of ~13° with a position angle of ~91° east of north. We also report low signal-to-noise ratio detections of an outer belt at a distance of ~1.5′′ (~52 au) from the star, of a spiral arm in the southern side of the star, and of a possible dusty clump at 0.11′′. These findings seem to persist over timescales of at least a year. Using the intensity images, we do not detect any planets in the close vicinity of the star, but the sensitivity reaches Jovian planet mass upper limits. We find that the SED is best reproduced with an inner disk at ~0.2′′ (~7 au) and another belt at 0.72′′ (25 au). Conclusions. We report the detections of several unexpected features in the disk around TWA 7. A yet undetected 100 Solar Mass planet with a semi-major axis at 20−30 au could possibly explain the outer belt as well as the spiral arm. We conclude that stellar winds are unlikely to be responsible for the spiral arm.

VLT/SPHERE IRDIS↗
NASA NTRS1988

A possible explanation for the inconsistency between the Giotto grain mass distribution and ground-based observations

Giotto measured the in situ Halley dust grain mass distribution with 2 instruments, Particle Impact Analyzer and Dust Impact Detection System (DIDSY), as well as the total intercepted mass from the deceleration of the spacecraft (Giotto Radio-Science Experiment, GRE). Ground based observations made shortly before encounter have fluxes much higher than would be predicted from Giotto data. It is concluded that Giotto DIDSY and GRE data represent observations of dust originating from a narrow track along the nucleus. They are consistent with ground based data, if assumptions are made about the level of activity along this track. The actual size distribution that should be used for modeling of the whole coma should not include the large mass excess actually observed by Giotto. Extrapolation of the small grain data should be used, since for these grains the velocity dispersion is low and temporal changes at the nucleus would not affect the shape of the mass distribution.

Perry, C. H.↗
NASA NTRS2017

Radar Detectability Studies of Slow and Small Zodiacal Dust Cloud Particles. III. The Role of Sodium and the Head Echo Size on the Probability of Detection

We present a path forward on a long-standing issue concerning the flux of small and slow meteoroids, which are believed to be the dominant portion of the incoming meteoric mass flux into the Earth's atmosphere. Such a flux, which is predicted by dynamical dust models of the Zodiacal Cloud, is not evident in ground-based radar observations. For decades this was attributed to the fact that the radars used for meteor observations lack the sensitivity to detect this population, due to the small amount of ionization produced by slow-velocity meteors. Such a hypothesis has been challenged by the introduction of meteor head echo (HE) observations with High Power and Large Aperture radars, in particular the Arecibo 430 MHz radar. Janches et al. developed a probabilistic approach to estimate the detectability of meteors by these radars and initially showed that, with the current knowledge of ablation and ionization, such particles should dominate the detected rates by one to two orders of magnitude compared to the actual observations. In this paper, we include results in our model from recently published laboratory measurements, which showed that (1) the ablation of Na is less intense covering a wider altitude range; and (2) the ionization probability, Beta ip, for Na atoms in the air is up to two orders of magnitude smaller for low speeds than originally believed. By applying these results and using a somewhat smaller size of the HE radar target we offer a solution that reconciles these observations with model predictions.

meteorites↗
NASA NTRS2015

Evaluation of CALIOP 532-nm Aerosol Optical Depth Over Opaque Water Clouds

With its height-resolved measurements and near global coverage, the CALIOP lidar onboard the CALIPSO satellite offers a new capability for aerosol retrievals in cloudy skies. Validation of these retrievals is difficult, however, as independent, collocated and co-temporal data sets are generally not available. In this paper, we evaluate CALIOP aerosol products above opaque water clouds by applying multiple retrieval techniques to CALIOP Level 1 profile data and comparing the results. This approach allows us to both characterize the accuracy of the CALIOP above-cloud aerosol optical depth (AOD) and develop an error budget that quantifies the relative contributions of different error sources. We focus on two spatial domains: the African dust transport pathway over the tropical North Atlantic and the African smoke transport pathway over the southeastern Atlantic. Six years of CALIOP observations (2007-2012) from the northern hemisphere summer and early fall are analyzed. The analysis is limited to cases where aerosol layers are located above opaque water clouds so that a constrained retrieval technique can be used to directly retrieve 532 nm aerosol optical depth and lidar ratio. For the moderately dense Sahara dust layers detected in the CALIOP data used in this study, the mean/median values of the lidar ratios derived from a constrained opaque water cloud (OWC) technique are 45.1/44.4 +/- 8.8 sr, which are somewhat larger than the value of 40 +/- 20 sr used in the CALIOP Level 2 (L2) data products. Comparisons of CALIOP L2 AOD with the OWC-retrieved AOD reveal that for nighttime conditions the L2 AOD in the dust region is underestimated on average by approx. 26% (0.183 vs. 0.247). Examination of the error sources indicates that errors in the L2 dust AOD are primarily due to using a lidar ratio that is somewhat too small. The mean/median lidar ratio retrieved for smoke is 70.8/70.4 +/- 16.2 sr, which is consistent with the modeled value of 70 +/- 28 sr used in the CALIOP L2 retrieval. Smoke AOD is found to be underestimated, on average, by approx. 39% (0.191 vs. 0.311). The primary cause of AOD differences in the smoke transport region is the tendency of the CALIOP layer detection scheme to prematurely assign layer base altitudes and thus underestimate the geometric thickness of smoke layers.

Liu, Z.↗
NASA NTRS2004

Effect of Palagonite Dust Deposition on the Automated Detection of Carbonate Vis/NIR Spectra

Currently Mars missions can collect more data than can be returned. Future rovers of increased mission lifetime will benefit from onboard autonomous data processing systems to guide the selection, measurement and return of scientifically important data. One approach is to train a neural net to recognize spectral reflectance characteristics of minerals of interest. We have developed a carbonate detector using a neural net algorithm trained on 10,000 synthetic Vis/NIR (350-2500 nm) spectra. The detector was able to correctly identify carbonates in the spectra of 30 carbonate and noncarbonate field samples with 100% success. However, Martian dust coatings strongly affect the spectral characteristics of surface rocks potentially masking the underlying substrate rock. In this experiment, we measure Vis/NIR spectra of calcite coated with different thicknesses of palagonite dust and evaluate the performance of the carbonate detector.

Gilmore, Martha S.↗
NASA NTRS2009

NASA Tech Briefs, March 2009

Topics covered include: Improved Instrument for Detecting Water and Ice in Soil; Real-Time Detection of Dust Devils from Pressure Readings; Determining Surface Roughness in Urban Areas Using Lidar Data; DSN Data Visualization Suite; Hamming and Accumulator Codes Concatenated with MPSK or QAM; Wide-Angle-Scanning Reflectarray Antennas Actuated by MEMS; Biasable Subharmonic Membrane Mixer for 520 to 600 GHz; Hardware Implementation of Serially Concatenated PPM Decoder; Symbolic Processing Combined with Model-Based Reasoning; Presentation Extensions of the SOAP; Spreadsheets for Analyzing and Optimizing Space Missions; Processing Ocean Images to Detect Large Drift Nets; Alternative Packaging for Back-Illuminated Imagers; Diamond Machining of an Off-Axis Biconic Aspherical Mirror; Laser Ablation Increases PEM/Catalyst Interfacial Area; Damage Detection and Self-Repair in Inflatable/Deployable Structures; Polyimide/Glass Composite High-Temperature Insulation; Nanocomposite Strain Gauges Having Small TCRs; Quick-Connect Windowed Non-Stick Penetrator Tips for Rapid Sampling; Modeling Unsteady Cavitation and Dynamic Loads in Turbopumps; Continuous-Flow System Produces Medical-Grade Water; Discrimination of Spore-Forming Bacilli Using spoIVA; nBn Infrared Detector Containing Graded Absorption Layer; Atomic References for Measuring Small Accelerations; Ultra-Broad-Band Optical Parametric Amplifier or Oscillator; Particle-Image Velocimeter Having Large Depth of Field; Enhancing SERS by Means of Supramolecular Charge Transfer; Improving 3D Wavelet-Based Compression of Hyperspectral Images; Improved Signal Chains for Readout of CMOS Imagers; SOI CMOS Imager with Suppression of Cross-Talk; Error-Rate Bounds for Coded PPM on a Poisson Channel; Biomorphic Multi-Agent Architecture for Persistent Computing; and Using Covariance Analysis to Assess Pointing Performance.

Source record↗
NASA NTRS1998

Submillimeter Imaging of Dust Around Main Sequence Stars

This grant was to image circumstellar dust disks surrounding main-sequence stars. The delivery of the SCUBA detector we had planned to use for this work was delayed repeatedly, leading us to undertake a majority of the observations with the UKT14 submillimeter detector at the JCMT (James Clerk Maxwell Telescope) and optical imagers and a coronagraph at the University of Hawaii 2.2-m telescope. Major findings under this grant include: (1) We discovered 5 asymmetries in the beta Pictoris regenerated dust disk. The discovery of these asymmetries was a surprise, since smearing due to Keplerian shear should eliminate most such features on timescales of a few thousand years. One exception is the "wing tilt" asymmetry, which we interpret as due to the scattering phase function of dust disk particles. From the wing tilt and a model of the phase function, we find a disk plane inclination to the line of sight of < 5 degrees. Other asymmetries (e.g. the butterfly asymmetry) suggest a disk that has been recently disturbed. We searched for possible nearby perturbers but found no clear candidates. Low mass stars (M dwarfs) and brown dwarfs would have fallen beneath the sensitivity threshhold of our survey, however. (2) We calculated a set of disk models to assess the detectability of dust disks around stars as a function of (a) distance, (b) disk, inclination (c) dust optical depth/mass, and (d) imaging resolution. These models guided our observational strategy on Mauna Kea. (3) We performed a coronagraphic survey of approx. 100 main-sequence stars in search of additional examples of circumstellar disks. The best new candidate disk, around the 5 M(sun) star BD+31deg.643, is distinguished by its large extent (few x 10( exp 3) AU). This disk, if real, cannot be rotationally supported. We suggest that the dust particles are ejected from a smaller, unseen disk (Kuiper Belt?) by strong radiation pressure forces due to the high luminosity central star. (4) SCUBA images of circumstellar dust disks were obtained at 850 gm in 1997/8. These images show extended, asymmetric emission, but have a signal-to-noise ratio too low to permit disk mapping to large projected distances. Our images of beta Pic, in particular, are in agreement with those obtained by Holland et al., and appear to confirm the blob-structure reported first by these authors. We have not yet been able to confirm that the structure is intrinsic to the disk, since beta Pic is at -50 degree declination, and suitable observing opportunities from northern latitudes are comparatively rare (even at the +20 degree latitude of JCMT). It is possible, for instance, that the main 850 micro-m blob is merely a galaxy or other high-z source projected onto the beta Pic mid-plane.

Jewitt, David↗
NASA NTRS1985

The gaseous component of the disk around Beta Pictoris

Optical spectra of alpha Lyr, alpha PsA, and beta Pic have been obtained at a velocity resolution of 3 km/s. No circumstellar absorption lines of Ca II or Na I are detected toward alpha Lyr or alpha PsA at sensitive limits. In the favorable case of beta Pic, where the circumstellar disk imaged by Smith and Terrile (1984) is seen nearly edge-on, a strong, narrow, circumstellar Ca II K absorption line previously reported by Slettebak (1982) and weaker, still narrower circumstellar Na I D lines are detected. Negative results of high sensitivity also are obtained for the Ca I 4226 A and CH(+) 4232 A lines, along with upper limits on the Zn II 2026, 2062 A doublet from archival IUE spectra. Under assumptions which agree with other well-established observations of the gaseous abundances of calcium and zinc, the total gaseous column density of hydrogen along a radius of the circumstellar disk is between 10 to the 18th and 4 x 10 to the 20th/sq cm. Within the boundaries of the dust disk detected by Smith and Terrile (1984) the total gaseous mass then is less than about 2, or less than 1 percent of the mass of the planetary system. A simplified model of the density distribution in the gaseous disk yields a characteristic total density n(H) of about 100,000/cu cm, which exceeds that of all interplanetary gas at earth's position by a factor of about 10,000.

Hobbs, L. M.↗
NASA NTRS1987

Evidence for first polymer in Comet Halley: Polyoxymethylene

The RPA2-Positive Ion Cluster Composition Analyzer (PICCA) on the Giotto spacecraft detected 5 mass peaks with regular spacing of 15 amu up to approximately 120 amu. Starting at 45 amu, the peaks decrease in intensity with increasing mass. Within their half-width they are in good agreement with dissociation products of formaldehyde polymer (POM). A production sequence in which cosmic radiation formed POM from water and carbon monoxide on grains that were aggregated into cometesimals is suggested. Other polymers, possibly containing CN, may also exist. Observations suggest that at least some of the H-, C-, and O-containing dust particles detected by the Particle Impact Analyzer (PIA) on board the Giotto spacecraft and its equivalent on the VEGA-1 and -2 spacecraft contain POM. The properties of POM are consistent with many of the unexpected observations in the coma.

Huebner, W. F.↗