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NASA NTRS2010

Experimental Investigation of Space Radiation Processing in Lunar Soil Ilmenite: Combining Perspectives from Surface Science and Transmission Electron Microscopy

Energetic ions mostly from the solar wind play a major role in lunar space weathering because they contribute structural and chemical changes to the space-exposed surfaces of lunar regolith grains. In mature mare soils, ilmenite (FeTiO3) grains in the finest size fraction have been shown in transmission electron microscope (TEM) studies to exhibit key differences in their response to space radiation processing relative to silicates [1,2,3]. In ilmenite, solar ion radiation alters host grain outer margins to produce 10-100 nm thick layers that are microstructurally complex, but dominantly crystalline compared to the amorphous radiation-processed rims on silicates [1,2,3]. Spatially well-resolved analytical TEM measurements also show nm-scale compositional and chemical state changes in these layers [1,3]. These include shifts in Fe/Ti ratio from strong surface Fe-enrichment (Fe/Ti >> 1), to Fe depletion (Fe/Ti < 1) at 40-50 nm below the grain surface [1,3]. These compositional changes are not observed in the radiation-processed rims on silicates [4]. Several mechanism(s) to explain the overall relations in the ilmenite grain rims by radiation processing and/or additional space weathering processes were proposed by [1], and remain under current consideration [3]. A key issue has concerned the ability of ion radiation processing alone to produce some of the deeper- penetrating compositional changes. In order to provide some experimental constraints on these questions, we have performed a combined X-ray photoelectron spectroscopy (XPS) and field-emission scanning transmission electron (FE-STEM) study of experimentally ion-irradiated ilmenite. A key feature of this work is the combination of analytical techniques sensitive to changes in the irradiated samples at depth scales going from the immediate surface (approx.5 nm; XPS), to deeper in the grain interior (5-100 nm; FE-STEM).

Christoffersen, R.↗

NASA NTRS2010

Discovery of X-Ray-Emitting O-Ne-Mg-Rich Ejecta in the Galactic Supernova Remnant Puppis A

We report on the discovery of X-ray-emitting O-Ne-Mg-rich ejecta in the middle-aged Galactic O-rich supernova remnant Puppis A with Chandra and XMM-Newton. We use line ratios to identify a low-ionization filament running parallel to the northeastern edge of the remnant that requires super-solar abundances, particularly for O, Ne, and Mg, which we interpret to be from O-Ne-Mg-rich ejecta. Abundance ratios of Ne/O, Mg/O, and Fe/O are measured to be [approx]2, [approx]2, and <0.3 times the solar values. Our spatially resolved spectral analysis from the northeastern rim to the western rim otherwise reveals sub-solar abundances consistent with those in the interstellar medium. The filament is coincident with several optically emitting O-rich knots with high velocities. If these are physically related, the filament would be a peculiar fragment of ejecta. On the other hand, the morphology of the filament suggests that it may trace ejecta heated by a shock reflected strongly off the dense ambient clouds near the northeastern rim.

Katsuda, Satoru↗

NASA NTRS2010

Solar Wind Sputtering of Lunar Surface Materials: Role and Some Possible Implications of Potential Sputtering

Solar-wind induced sputtering of the lunar surface includes, in principle, both kinetic and potential sputtering. The role of the latter mechanism, however, in many focused studies has not been properly ascertained due partly to lack of data but can also be attributed to the assertion that the contribution of solar-wind heavy ions to the total sputtering is quite low due to their low number density compared to solar-wind protons. Limited laboratory measurements show marked enhancements in the sputter yields of slow-moving, highly-charged ions impacting oxides. Lunar surface sputtering yields are important as they affect, e.g., estimates of the compositional changes in the lunar surface, its erosion rate, as well as its contribution to the exosphere as well as estimates of hydrogen and water contents. Since the typical range of solar-wind ions at ~1 keV/amu is comparable to the thickness of the amorphous rim found on lunar soil grains, i.e. ~ few 10s nm, lunar simulant samples JSC-1A AGGL are specifically enhanced to have such rims in addition to the other known characteristics of the actual lunar soil particles. However, most, if not all laboratory studies of potential sputtering were carried out in single crystal targets, quite different from the rim s amorphous structure. The effect of this structural difference on the extent of potential sputtering has not, to our knowledge, been investigated to date.

Barghouty, A. F.↗

NASA NTRS2012

Coordinated Analyses of Mineral-organic Matter Associations in Interplanetary Dust Particles

Little is known about the timing and processes involved in the incorporation of organic matter with inorganic materials in early Solar System bodies. Recently, X-ray absorption near-edge spectroscopy (XANES) studies showed carbon-rich rims surrounding individual mineral grains in anhydrous IDPs [1,2]. These carbonaceous rims are believed to have formed prior to parent body formation and likely served to bond mineral grains during accretion into larger aggregates. We are exploring the nature of these carbonaceous rims through coordinated analyses of their chemistry, mineralogy, spectroscopy and isotopic characteristics. Here we report our preliminary mineralogical observations.

Nakamura-Messenger, K.↗

NASA NTRS2013

Microchemical and Structural Evidence for Space Weathering in Soils from Asteroid Itokawa

The chemistry, microstructure and optical properties of grains on the surfaces of airless bodies are continu-ously modified due to their interactions predominantly with solar energetic ions and micrometeorite impacts. Collectively known as space weathering, this phenomenon results in a discrepancy between remotely sensed spectra from asteroids and those ac-quired directly from meteorites. The return of pristine samples from the asteroid Itokawa provides insight into surface processes on airless bodies and will help in correlating remote sensing data with laboratory analysis of meteorites. Samples and Methods: We examined Itokawa samples RA-QD02-0042-01 and RA-QD-02-0042-02, ultramicrotomed sec-tions of a singular grain prepared by the Hayabusa sample cura-tion team. We analyzed these slices using a 200 keV JEOL 2010F transmission electron microscope (TEM) at Arizona State Uni-versity and a 200 keV JEOL 2500SE TEM at NASA JSC. Both field emission TEMs are equipped with energy-dispersive X-ray spectrometers (EDS) and scanning TEM (STEM) detectors. Results and Discussion: TEM observations reveal that the sectioned grain predominantly consists of a single crystal of low-Ca orthopyroxene, with subsidiary smaller regions of olivine, Fe-Ni sulfide, and Fe-Ni metal. EDS-spectrum imaging and high-resolution TEM (HRTEM) show local, nanocrystalline regions of the outermost 2 to 5 nm of the pyroxene are composed of an Fe-Mg-S-rich and Si- and O-depleted layer that is underlain by a 2- to 5-nm thick amorphous zone enriched in Si. These layers occur in multiple microtome slices and have uniform thicknesses. We also observe localized 'islands' of material on the surface of the pyroxene which HRTEM imaging indicates are amorphous and EDS measurements show are compositionally heterogeneous. A 10- to 60-nm thick partially amorphous zone occurs below the compositionally distinct rim. While this this zone is associated with the compositionally heterogeneous outer layer, it also occurs as a local stand-alone feature on the exterior rim of the grain. Ar-eas of the pyroxene grain rim also exhibit a vesicular texture. The TEM data indicate a complex history of space weather-ing for samples RA-QD02-0042-01 and -02. The outermost layer of nanocrystalline material with varied composition is consistent with previously suggested [3-4] chemical and structural pro-cessing by solar wind ions, with a possible additional role for im-pact vapor deposition [3-4]. The amorphous and compositionally distinct islands on the surface of this grain, similar to lunar glasses, suggest formation through vapor deposition via micrometeor-ite impact events. In comparison, the amorphization and vesicula-tion textures are likely a product of radiation damage from the solar wind. The depth and degree of amorphization, in conjunction with model calculations, will help provide an upper limit on exposure time for these particles.

Thompson, M. S.↗

NASA NTRS2013

Space Weathering of Lunar Rocks and Regolith Grains

The exposed surfaces of lunar soil grains and lunar rocks become modified and coated over time with a thin rind of material (patina) through complex interactions with the space environment. These interactions encompass many processes including micrometeorite impacts, vapor and melt deposition, and solar wind implantation/sputtering effects that collectively are referred to as "space weathering". Studies of space weathering effects in lunar soils and rocks provide important clues to understanding the origin and evolution of the lunar regolith as well as aiding in the interpretation of global chemical and mineralogical datasets obtained by remote-sensing missions. The interpretation of reflectance spectra obtained by these missions is complicated because the patina coatings obscure the underlying rock mineralogy and compositions. Much of our understanding of these processes and products comes from decades of work on remote-sensing observations of the Moon, the analysis of lunar samples, and laboratory experiments. Space weathering effects collectively result in a reddened continuum slope, lowered albedo, and attenuated absorption features in reflectance spectra of lunar soils as compared to finely comminuted rocks from the same Apollo sites. Space weathering effects are largely surface-correlated, concentrated in the fine size fractions, and occur as amorphous rims on individual soil grains. Rims on lunar soil grains are highly complex and span the range between erosional surfaces modified by solar wind irradiation to depositional surfaces modified by the condensation of sputtered ions and impact-generated vapors. The optical effects of space weathering effects are directly linked to the production of nanophase Fe metal in lunar materials]. The size of distribution of nanophase inclusions in the rims directly affect optical properties given that large Fe(sup o) grains (approx 10 nm and larger) darken the sample (lower albedo) while the tiny Fe(sup o) grains (<5nm) are the primary agent in spectral "reddening". More recent work has focused on the nature and abundance of OH/H2O in the lunar regolith using orbital data and samples analyses. Advances in sample preparation techniques have made possible detailed analyses of patina-coated rock surfaces. Major advances are occurring in quantifying the rates and efficiency of space weathering processes through laboratory experimentation.

Keller, L. P.↗

NASA NTRS2013

The Pinnacles of Callisto

Many regions of Callisto feature an unusual landscape consisting of rolling dark plains with interspersed bright knobs (pinnacles) and ridges. In earlier work we interpreted the dark plains as dusty, mass-wasted residue from sublimation from volatile-rich bedrock and the bright knobs (often crater rims) as water ice accumulations at locations sheltered from thermal reradiation from the dusty residue. We simulated evolution of Callisto's craters as a combination of bedrock volatile sublimation, mass wasting of the dark, non-coherent residue, and redeposition of ice, and concluded that the ice pinnacles and ridges might be underlain by tens to hundreds of meters of ice. Here we report the initial work of a new study of pinnacles addressing additional questions: 1) Is there an evolutionary sequence starting, e.g., from a cratered initial surface through growth and formation of a dust mantle and pinnacles, to eventual loss of ice to sublimation resulting in just a dark, dusty surface? 2) What determines the areal density and spatial scale of pinnacles - volatile content of bedrock, crater density, surface age, broad-scale topographic setting? 3) Are pinnacles still forming? Several observations address these questions. In a few places scattered high-albedo blocks approx. 25-60 m in diameter occur in the vicinity of large icy pinnacles. We interpret these blocks to be remnants from the collapse of tall pinnacles that were undermined by mass wasting. Some high-relief icy knobs have developed a skeletonized planform due to mass wasting by avalanching, or perhaps to seeding of new sites of ice deposition on mass-wasted ice blocks. Some areas nearly lack fresh craters with well-defined ejecta and ice-free rims. This may imply rapid transformation of fresh craters by sublimation, mass wasting, and ice reprecipitation. In other areas small sharp-rimmed craters occur which lack ice pinnacles, but the craters nonetheless lack visible ejecta sheets. Our preliminary interpretation is that mass wasting is very efficient on Callisto, or alternatively the dust cover is very thick and lacks competent coarse materials.

bedrock volatile sublimation↗

NASA NTRS2014

Recent Results From the Opportunity Rover's Exploration of Endeavour Crater, Mars

The Mars Exploration Rover Opportunity is beginning its 11th year of exploration and as of sol 3535 (1/3/14 UTC) has traversed 38,729 m (based on wheel turns) across the plains of Meridiani and the rim of the approx. 22 km wide Noachian Endeavour Crater. Opportunity has investigated ancient sulfate-rich sand-stones (Burns formation) that dominate the plains and formed in ancient playa and dune environments, characterized impact breccias (Shoemaker formation) and their aqueous alteration on Endeavour's Cape York rim segment, and investigated extensive aqueous alteration of rocks on Cape York's Matijevic Hill that stratigraphically underlie Shoemaker formation and predate the Endeavour-forming event. In this abstract results from Opportunity's recent exploration of Endeavour's rim are covered, focusing on comparing what was found on Matijevic Hill with observations acquired on Murray Ridge, where Opportunity will spend its sixth winter at Cook Haven.

Arvidson, R. E.↗

NASA NTRS2015

Noachian Impact Ejecta on Murray Ridge and Pre-impact Rocks on Wdowiak Ridge, Endeavour Crater, Mars: Opportunity Observations

Mars Exploration Rover Opportunity has been exploring Meridiani Planum since January 2004, and has completed 4227% of its primary mission. Opportunity has been investigating the geology of the rim of 22 km diameter Endeavour crater, first on the Cape York segment and now on Cape Tribulation. The outcrops are divided York; (ii) the Shoemaker fm, impact breccias representing ejecta from the crater; into three formations: (i) the lower Matijevic fm, a pre-impact lithology on Cape and (iii) the upper Grasberg fm, a post-impact deposit that drapes the lower portions of the eroded rim segments. On the Cape Tribulation segment Opportunity has been studying the rocks on Murray Ridge, with a brief sojourn to Wdowiak Ridge west of the rim segment. team member Thomas Wdowiak, who died in 2013.) One region of Murray Ridge has distinctive CRISM spectral characteristics indicating the presence of a small concentration of aluminous smectite based on a 2.2 micron Al-OH combination band (hereafter, the Al-OH region).

Mittlefehldt, D. W.↗

NASA NTRS2014

Global Distribution of Lunar Impact Melt Flows

In this study, we analyzed the distribution and properties of 146 craters with impact melt deposits exterior to their rims. Many of these craters were only recently discovered due to their unusual radar properties in the near-global Mini-RF data set. We find that most craters with exterior deposits of impact melt are small, less than 20 kilometers, and that the smallest craters have the longest melt flows relative to their size. In addition, exterior deposits of impact melt are more common in the highlands than the mare. This may be the result of differing target properties in the highlands and mare, the difference in titanium content, or the greater variation of topography in the highlands. We find that 80 percent of complex craters and 60 percent of simple craters have melt directions that are coincident or nearly coincident with the lowest point in their rim, implying that pre-existing topography plays a dominant role in melt emplacement. This is likely due to movement during crater modification (complex craters) or breached crater rims (simple craters). We also find that impact melt flows have very high circular polarization ratios compared to other features on the Moon. This suggests that their surfaces are some of the roughest material on the Moon at the centimeter to decimeter scale, even though they appear smooth at the meter scale.

Cratering↗

NASA NTRS2016

Similarities Across Mars: Acidic Fluids at Both Meridiani Planum and Gale Crater in the Formation of Magnesium-Nickel Sulfates

In-situ identification of sulfates at the martian surface by the Mars Exploration Rovers and the Mars Science Laboratory have included calcium sulfates with various states of hydration (gypsum, bassanite, anhydrite), iron sulfates of likely fumarolic origin, massive deposits of iron hydroxysulfates indicative of an acidic history, and minor occurrences of magnesium sulfates. Recent measurements by the Opportunity and Curiosity Alpha Particle X-ray Spectrometers (APXS) have indicated the presence of Ni-substituted Mg-sulfates at the Meridiani Planum and Gale Crater landing sites. The Opportunity rover has traversed nearly 43 km and is currently exploring the impact breccias of the rim of Endeavour crater, near a location where signatures of aqueous alteration have been established from orbit. APXS analyses of subsurface materials excavated by a rover wheel show clear evidence for a Mg(Ni)-sulfate with Mg:Ni (is) approximately 100:1 (molar). On the other side of the planet, Curiosity is continuing its climb up Mount Sharp after driving (is) approximately 13 km since landing. Over the last 4 km of the traverse, there have been multiple chemical analyses of erosionally-resistant nodules and dendritic features in a finely laminated mudstone unit which also indicate Mg(Ni)-sulfate (Mg:Ni (is) approximately 30:1, molar). The geologic settings for the Endeavour rim and the Mount Sharp mudstones are clearly different, but similar formation conditions for these sulfates may be possible. Ni(2+) readily substitutes for Mg(2+) in a variety of geochemical processes due to their comparable ionic radii. The availability of soluble Ni at the time of Mg-sulfate precipitation suggests acidic solutions. The fluids responsible for alteration in the Endeavour rim and for the formation of nodules in Gale mudstones may have had similar chemical characteristics at the time the Mg-sulfates were formed.

Yen, Albert S.↗

NASA NTRS2017

Illumination Conditions at the Lunar Poles: Implications for Future Exploration

We produced 400 x 400 km Digital Terrain Models (DTMs) of the lunar poles from Lunar Orbiter Laser Altimeter (LOLA) ranging measurements. To achieve consistent, high-resolution DTMs of 20 m/pixel the individual ranging profiles were adjusted to remove small track-to-track o sets. We used these LOLADTMs to simulate illumination conditions at surface level for 50 x 50 km regions centered on the poles. Illumination was derived in one-hour increments from 01 January, 2017 to 01 January, 2037 to cover the lunar precessional cycle of 18.6 years and to determine illumination conditions over several future mission cycles. We identified three regions receiving high levels of illumination at each pole, e.g. the equator-facing crater rims of Hinshelwood, Peary and Whipple for the north pole and the rim of Shackleton crater, and two locations on a ridge between Shackleton and de Gerlache crater for the south pole. Their average illumination levels range from 69.5% to 82.9%, with the highest illumination levels found at the north pole on the rim of Whipple crater. A more detailed study was carried out for these sites as targets for a lander and/or rover equipped with solar arrays. For this purpose we assumed a lander with a structural height of two meters above the ground (height of the solar panels). Here average illumination levels range from 77.1% to 88.0%, with the maximum found at the ridge between Shackleton and de Gerlache crater on the south pole. Distances, sizes and slopes of nearby Permanently Shadowed Regions (PSRs) as a prime science target were also assessed in this case.

LOLA↗

NASA NTRS2017

RTAPS (Research and Technology for Aerospace Propulsion Systems): Simulation of Structural Loads within a Hybrid Gear Resulting From Loading at the Gear Teeth

This report investigates the practical usage of hybrid structures for rotorcraft gearing. The primary driver for utilizing hybrid structures for rotorcraft gearing is to reduce the drive system weight. The hybrid structure concept featured in this study for rotorcraft gearing consists of a metallic gear tooth-rim, a web section manufactured from composite materials, and a metallic hub. The metallic gear tooth-rim is manufactured from conventional gear steel alloys, such as AISI 9310. The gear tooth-rim attaches to the outer diameter of the web section made from composite materials. The inner diameter of the composite web can then attach to a metallic hub, completing the assembly. It is assumed that areas of the shafting or hub where rolling element bearings may ride must remain as gear steel alloys for this study.

Hybrid Structures↗

NASA NTRS2017

RTAPS (Research and Technology for Aerospace Propulsion Systems): Simulation of Structural Loads within a Hybrid Gear Resulting From Loading at the Gear Teeth

Naffin, Richard K.↗

NASA NTRS2019

Static Torsion Testing and Modeling of a Variable Thickness Hybrid Composite Bull Gear

Torsional strength of a variable thickness hybrid gear web was measured by performing static testing on the part in a large torsion test frame. The outer rim of the hybrid gear web was fixed to the bottom of the test frame and loading was applied to the web through a shaft. The test setup included the installation of digital image correlation (DIC) systems to obtain deformation and strain measurements from the surfaces of the hybrid gear web and the mechanical test equipment to ensure reliability of the test. The results indicated that the variable thickness hybrid gear web achieved approximately twice the torsional strength compared to that of previous hybrid gear designs. The DIC analysis showed significantly more straining of the loading shaft than the actual test article. Additionally, the results demonstrated the importance and affect that the metallic, lobed interlock features had on the principal strain and out-of-plane displacement fields. The analysis revealed that the fixed outer rim was in fact rotating and a rigid body motion compensation (RBMC) function was computed to determine the actual rotation of the hub and composite web relative to the outer rim. Modeling simulations were performed for the variable thickness hybrid gear web and correlated well with the RBMC rotational deformation seen in the DIC analysis. In addition to benchmarking the load capacity of the hybrid gear web, measuring its strength is useful information to define the parameters needed for dynamic, endurance, and other testing of the part.

Johnston, Joel P.↗

NASA NTRS2020

AQUIFER Nano-Electrofuel Energy Economy and Powered Aircraft Operations

The Aqueous, QUick-charging battery Integration For Electric flight Research project is explained and the major subsystems are described, including nano-electric fluid, rim-driven motors, and integration concepts. The nano-electric fluid concept is a new type of aqueous flow battery that could reduce or retire the fire and explosion hazards of conventional batteries and fuel cells. The nano-electric fluid itself could enable energy storage and increased available energy per fuel weight ratios. The rim-driven motor is being developed to improve propulsion system safety and stability and to reduce noise. The rim-driven motor concept could enable motors that are more efficient both electrically and aerodynamically. The Energy Economy of the project concept is presented as a potential renewable or green energy sustainment for utilizing in-place infrastructure. The nano-electric fluid energy charge-use-recharge cycle is presented using renewable energy input from solar, wind, and hydroelectricity. Powered aircraft operations are presented, and the logistics of the new nano-electric fluid technology are explored. Powered aircraft operations topics include weight and balance, fueling, recharging, safety, and derivative considerations.

Lechniak, Jason A.↗

NASA NTRS2020

An Impact Crater Origin for the InSight Landing Site at Homestead Hollow, Mars: Implications for Near Surface Stratigraphy, Surface Processes, and Erosion Rates

The InSight mission to Mars landed within Homestead hollow on an Early Amazonian lavaplain. The hollow is a 27‐m‐diameter, 0.3‐m‐deep quasi‐circular depression that shares morphologic and sedimentologic characteristics to degraded impact craters. Unlike the intercrater plains outside of the hollow, the interior lacks cobbles and is dominated by loose sand, granules, and pebbles. Fresher craters near the landing site exhibit meter‐scale bedforms in their ejecta and on their floors due to sediment trapping.The sedimentology of the interior fill of Homestead hollow suggests similar trapping. The hollow falls along amorphologic continuum that requires low rates of rim degradation and fill. Crater degradation rates (rim erosion plus filling) in the landing site decline nonlinearly through time from 10−2to 10−4m/Myr as craters evolve to a hollow‐like form. Rim erosion rates are lower initially, at 10−3m/Myr, but converge with degradation rates to 10−4m/Myr. This implies that while filling plays an important role soon after crater formation, it is limited in later stages. Crater statistics indicate that the bulk of the fill occurred in the first~50 Myr for Homestead hollow. The estimated maximum age of the hollow is ~400 to 700 Myr. This requires near‐zero fill aggradation and long‐term soil stability for the bulk of the crater's history. Fill stability manifests in Homestead hollow as a ~5‐to 10‐cm‐thick duricrust, formed by exchanges of atmospheric water vapor with soil. The estimated degradation in the hollow requires ~2 to 3 m of sedimentary fill beneath the lander.

Maria Elaine Banks↗

NASA NTRS2022

VLTI-MATISSE L- and N-Band Aperture-Synthesis Imaging of the Unclassified B[e] star FS Canis Majoris

Context. FS Canis Majoris (FS CMa, HD 45677) is an unclassified B[e] star surrounded by an inclined dust disk. The evolutionary stage of FS CMa is still debated. Perpendicular to the circumstellar disk, a bipolar outflow was detected. Infrared aperture-synthesis imaging provides us with a unique opportunity to study the disk structure. Aims. Our aim is to study the intensity distribution of the disk of FS CMa in the mid-infrared L and N bands. Methods. We performed aperture-synthesis imaging of FS CMa with the MATISSE instrument (Multi AperTure mid-Infrared SpectroScopic Experiment) in the low spectral resolution mode to obtain images in the L and N bands. We computed radiative transfer models that reproduce the L- and N-band intensity distributions of the resolved disks. Results. We present L- and N-band aperture-synthesis images of FS CMa reconstructed in the wavelength bands of 3.4–3.8 and 8.6–9.0 μm. In the L-band image, the inner rim region of an inclined circumstellar disk and the central object can be seen with a spatial resolution of 2.7 milliarcsec (mas). An inner disk cavity with an angular diameter of ~6 × 12 mas is resolved. The L-band disk consists of a bright northwestern (NW) disk region and a much fainter southeastern (SE) region. The images suggest that we are looking at the bright inner wall of the NW disk rim, which is on the far side of the disk. In the N band, only the bright NW disk region is seen. In addition to deriving the inclination and the inner disk radius, fitting the reconstructed brightness distributions via radiative transfer modelling allows one to constrain the innermost disk structure, in particular the shape of the inner disk rim.

techniques↗