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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2005

Observations of Hydrated Minerals on Asteroids: Pushing Back the Frontiers

The three accomplishments during this grant include: 1) Travel to 2004 Division of Planetary Science (of American Astronomical Society) Conference in Louisville, KY and presentation of Rotationally resolved spectroscopy of Vesta in the 1-4 micron region, abstract 28.07. 2) Remote observations using the IRTF on 20-21 June 2004 and 28-3 1 August 2004, and reduction of data as described in the grant proposal and descoping document. These observations confirm the presence of two different band shapes among C-class asteroid spectra in the 3-micron region. This allowed a revision of the known distribution of Ceres- and Pallas-type objects. 3) Remote observations using the IRTF on 7-10 August 2004. These observations of Vesta were presented, and the manuscript will be submitted to Icarus in June.

Source record↗
NASA NTRS2008

Multi-wavelength Observations and Modelling of a Solar Flare

Aims: The aim of this work is to investigate the dynamic behavior of a C-class solar flare through the evolution of temperature, emission measure, energy loss and velocity. In particular, the variation of these properties with time are studied using multi-wavelength observations in combination with a recently developed 0-D hydrodynamic model. Methods: The temperature and emission measure evolution were studied using several instruments covering a wide range of temperatures - the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI, >5 MK), GOES-12 (5- 30 MK), the Transition Region and Coronal Explorer (TRACE 171 A, 1 MK) and the Coronal Diagnostic Spectrometer (CDS, 0.03-8 MK). The temperature and emission measure were analysed through the systematic cooling of flare plasma through the response functions of these instruments. These parameters were then investigated using the Enthalpy Based Thermal Evolution of Loops model (EBTEL). The Doppler shifts at both flare footpoints were analysed using five emission lines seen by CDS. Results: The flare began with clear evidence for pre-flare heating. Upflows of approx.90 km/s and low level emission, both observed in Fe XIX before the main impulsive phase were explained by pre-flare gentle chromospheric evaporation. During the main impulsive phase, the flare plasma was heated to a temperature of >13 MK in approximately 10 minutes. Explosive chromospheric evaporation was observed, driving upflows of approx.80 km/s in Fe XIX and simultaneous downflows of approx.20 km/s in He I and O v. At the peak of the Rare, conduction modelled by EBTEL was found to be the dominant loss mechanism, working efficiently to both lower the temperatures and drive gentle chromospheric evaporation. As the temperature fell below approx.8 MK, radiation became the dominant loss mechanism. During the final stages of the decay phase, downflowing plasma was observed at the footpoints in He I, O v and Mg x at velocities of up to approx.40 km/s, suggesting loop draining occurred. Conclusions. This is the first extensive study of the evolution of flare plasma using both spectroscopic and broad-band instruments in conjunction with a comprehensive hydrodynamic model. The flare began with pre-flare heating and then evolved following the predictions of the standard flare model. Detailed analysis of the plasma heating mechanisms was carried out and the heating function most consistent with observations was found to be Gaussian in shape. The simulations suggested that both direct heating and heating by a non-thermal beam played significant roles in this event.

Raftery, Claire L.↗
NASA NTRS2009

Velocity Characteristics of Evaporated Plasma using Hinode/EIS

This paper presents a detailed study of chromospheric evaporation using the EUV Imaging Spectrometer (EIS) onboard Hinode in conjunction with HXR observat,ions from RHESSI. The advanced capabilities of EIS were used to measure Doppler shifts in 15 emission lines covering the temperature range T=0.05-16 MK during the impulsive phase of a C-class flare on 2007 December 14. Blueshifts indicative of the evaporated material were observed in six emission lines from Fe XIV-XXIV (2-16 MK). Upflow velocity was found to scale with temperature as v(sub up) (kilometers per second) approximately equal to 5-17 T (MK). Although the hottest emission lines, Fe XXIII and Fe XXIV, exhibited upflows of greater than 200 kilometers per second, their line profiles were found to be dominated by a stationary component in stark contrast to the predictions of the standard flare model. Emission from O VI-Fe XIII lines (0.5-1.5 MK) was found to be redshifted by v(sub down) (kilometers per second) approximately equal to 60-17 T (MK) and was interpreted as the downward-moving 'plug' characteristic of explosive evaporation. These downflows occur at temperatures significantly higher than previously expected. Both upflows and downflows were spatially and temporally correlated with HXR emission observed by RHESSI that provided the properties of the electron beam deemed to be the driver of the evaporation. The energy contained in the electron beam was found to be greater than or equal to 10(sup 11) ergs per square centimeter per second consistent with the value required to drive explosive chromospheric evaporation from hydrodynamic simulations.

Milligan, Ryan O.↗
NASA NTRS2010

The Connection Between Small Gamma-Ray Flares and SEPs with COMPTEL/CGRO

While it is clear that particle acceleration is occurring during flares, what is less clear is the connection between the neutral radiation observed concommitant with the flare and the in-situ observations of SEPs. For the largest SEP events, where current instruments possess the sensitivity to observe nuclear-related gamma-ray emission, the origin of SEPs is generally divided between an escaping accelerated flare population and a population of coronal particles (or some admixture) accelerated through CME-driven shocks. Small flares, as defined by their X-ray emission, have been found to correlate with the presence of small "impulsive" (enriched in electrons and heavy nuclei) SEP events, suggesting that small SEP events are originally flare particles. The difficulty with this interpretation is that small flares lack detectable nuclear-related gamma-ray emission. Whether this emission is there or not is unclear because current instruments capable of high-energy gamma-ray observations operate above the sensitivity threshold for observing gammaray emission from small flares (< C-class). The COMPton TELescope (COMPTEL) aboard the Compton Gamma Ray Observatory (CGRO) provided unprecedented, and as yet unsurpassed, sensitivity to y rays in the 0.7 to 30 MeV energy range and neutrons in the 20 to 150 MeV energy range. This, combined with its nine years of operation, has produced a unique data set of observations for almost a complete solar cycle. The COMPTEL archival data offers the best possibility to investigate a connection between SEP observations in space and small-flare gamma-ray emission. We present preliminary results of a small-flare search within the COMPTEL archival data and discuss the correlation between already well-established compilations of SEP events and small impulsive or 3He-rich SEP events. Establishing a connection and determining the characterization of this connection, would signify an important development in our understanding of how and where flare particles are accelerated and how these very same particles escape into the interplanetary medium. Equally important would be demonstrating the inconsistencies or poor correlation between gamma-ray emission and small impulsive SEP events.

deNolfo, Georgia↗
NASA NTRS2013

Advanced Curation of Current and Future Extraterrestrial Samples

Curation of extraterrestrial samples is the critical interface between sample return missions and the international research community. Curation includes documentation, preservation, preparation, and distribution of samples. The current collections of extraterrestrial samples include: Lunar rocks / soils collected by the Apollo astronauts Meteorites, including samples of asteroids, the Moon, and Mars "Cosmic dust" (asteroid and comet particles) collected by high-altitude aircraft Solar wind atoms collected by the Genesis spacecraft Comet particles collected by the Stardust spacecraft Interstellar dust collected by the Stardust spacecraft Asteroid particles collected by the Hayabusa spacecraft These samples were formed in environments strikingly different from that on Earth. Terrestrial contamination can destroy much of the scientific significance of many extraterrestrial materials. In order to preserve the research value of these precious samples, contamination must be minimized, understood, and documented. In addition the samples must be preserved - as far as possible - from physical and chemical alteration. In 2011 NASA selected the OSIRIS-REx mission, designed to return samples from the primitive asteroid 1999 RQ36 (Bennu). JAXA will sample C-class asteroid 1999 JU3 with the Hayabusa-2 mission. ESA is considering the near-Earth asteroid sample return mission Marco Polo-R. The Decadal Survey listed the first lander in a Mars sample return campaign as its highest priority flagship-class mission, with sample return from the South Pole-Aitken basin and the surface of a comet among additional top priorities. The latest NASA budget proposal includes a mission to capture a 5-10 m asteroid and return it to the vicinity of the Moon as a target for future sampling. Samples, tools, containers, and contamination witness materials from any of these missions carry unique requirements for acquisition and curation. Some of these requirements represent significant advances over methods currently used. New analytical and screening techniques will increase the value of current sample collections. Improved web-based tools will make information on all samples more accessible to researchers and the public. Advanced curation of current and future extraterrestrial samples includes: Contamination Control - inorganic / organic Temperature of preservation - subfreezing / cryogenic Non-destructive preliminary examination - X-ray tomography / XRF mapping / Raman mapping Microscopic samples - handling / sectioning / transport Special samples - unopened lunar cores Informatics - online catalogs / community-based characterization.

Allen, Carlton C.↗
NASA NTRS2014

Water Transport and the Evolution of CM Parent Bodies

Extraterrestrial water-bearing minerals are of great importance both for understanding the formation and evolution of the solar system and for supporting future human activities in space. Asteroids are the primary source of meteorites, many of which show evidence of an early heating episode and varying degrees of aqueous alteration. The origin and characterization of hydrated minerals (minerals containing H2O or OH) among both the main-belt and near-earth asteroids is important for understanding a wide range of solar system formation and evolutionary processes, as well as for planning for human exploration. Current hypotheses postulate asteroids began as mixtures of water ice and anhydrous silicates. A heating event early in solar system history was then responsible for melting the ice and driving aqueous alteration. The link between asteroids and meteorites is forged by reflectance spectra, which show 3-μm bands indicative of bound OH or H2O on the C-class asteroids, which are believed to be the parent bodies of the carbonaceous chondrites in our collections. The conditions at which aqueous alteration occurred in the parent bodies of carbonaceous chondrites are thought to be well-constrained: at 0-25 C for less than 15 Myr after asteroid formation. In previous models, many scenarios exhibit peak temperatures of the rock and co-existing liquid water in more than 75 percent of the asteroid's volume rising to 150 C and higher, due to the exothermic hydration reactions triggering a thermal runaway effect. However, even in a high porosity, water-saturated asteroid very limited liquid water flow is predicted (distances of 100's nm at most). This contradiction has yet to be resolved. Still, it may be possible for water to become liquid even in the near-surface environment, for a long enough time to drive aqueous alteration before vaporizing or freezing then subliming. Thus, we are using physics- and chemistry-based models that include thermal and fluid transport as well as the effects of relevant chemical reactions, to investigate whether formation of hydrated minerals can occur in the surface and near-surface environments of carbonaceous type asteroids. These models will elucidate how the conditions within the parent body that cause internal aqueous alteration play themselves out at the asteroid's surface. We are using our models to determine whether the heat budget of 20-100-km bodies is sufficient to bring liquid water to the near-surface and cause mineral alteration, or whether additional heat input at the surface (i.e, by impacts) is needed to provide a transient liquid water source for mineral hydration without large- scale liquid water transport.

Coker, R.↗
NASA NTRS2012

Radar-Enabled Recovery of the Sutters Mill Meteorite, a Carbonaceous Chondrite Regolith Breccia

Doppler weather radar imaging enabled the rapid recovery of the Sutter's Mill meteorite after a rare 4-kiloton of TNT-equivalent asteroid impact over the foothills of the Sierra Nevada in northern California. The recovered meteorites survived a record high-speed entry of 28.6 kilometers per second from an orbit close to that of Jupiter-family comets (Tisserand's parameter = 2.8 +/- 0.3). Sutter's Mill is a regolith breccia composed of CM (Mighei)-type carbonaceous chondrite and highly reduced xenolithic materials. It exhibits considerable diversity of mineralogy, petrography, and isotope and organic chemistry, resulting from a complex formation history of the parent body surface. That diversity is quickly masked by alteration once in the terrestrial environment but will need to be considered when samples returned by missions to C-class asteroids are interpreted.

Radar↗
NASA NTRS2015

CM Carbonaceous Chondrite Lithologies and Their Space Exposure Ages

The CMs are the most commonly falling C chondrites, and therefore may be a major component of C-class asteroids, the targets of several current and future space missions. Previous work [1] has concluded that CM chondrites fall into at least four distinct cosmic ray space exposure (CRE) age groups (0.1 million years, 0.2 million years, 0.6 million years and greater than 2.0 million years), an unusually large number, but the meaning of these groupings is unclear. It is possible that these meteorites came from different parent bodies which broke up at different times, or instead came from the same parent body which underwent multiple break-up events, or a combination of these scenarios, or something else entirely. The objective of this study is to investigate the diversity of lithologies which make up CM chondrites, in order to determine whether the different exposure ages correspond to specific, different CM lithologies, which permit us to constrain the history of the CM parent body(ies). We have already reported significant petrographic differences among CM chondrites [2-4]. We report here our new results.

Zolensky, Michael↗
NASA NTRS2015

Large Solar Energetic Particle Events Associated With Filament Eruptions Outside Active Regions

We report on four large filament eruptions (FEs) from solar cycles 23 and 24 that were associated with large solar energetic particle (SEP) events and interplanetary type II radio bursts. The post-eruption arcades corresponded mostly to C-class soft X-ray enhancements, but an M1.0 flare was associated with one event. However, the associated coronal mass ejections (CMEs) were fast (speeds approx. 1000 km/s) and appeared as halo CMEs in the coronagraph field of view. The interplanetary type II radio bursts occurred over a wide wavelength range, indicating the existence of strong shocks throughout the inner heliosphere. No metric type II bursts were present in three events, indicating that the shocks formed beyond 2-3 Rs. In one case, there was a metric type II burst with low starting frequency, indicating a shock formation height of approx.2 Rs. The FE-associated SEP events did have softer spectra (spectral index >4) in the 10-100 MeV range, but there were other low-intensity SEP events with spectral indices ⩾4. Some of these events are likely FE-SEP events, but were not classified as such in the literature because they occurred close to active regions. Some were definitely associated with large active region flares, but the shock formation height was large. We definitely find a diminished role for flares and complex type III burst durations in these large SEP events. Fast CMEs and shock formation at larger distances from the Sun seem to be the primary characteristics of the FE-associated SEP events.

filaments↗
NASA NTRS2016

C Chondrite Clasts in H Chondrite Regolith Breccias: Something Different

Zag (H3-6) and Monahans (1998) (H5) are regolith breccias that contain 4.5 GY old halite crystals which in turn contain abundant inclusions of aqueous fluids, solids and organics [1-4]. We have previously proposed that these halites originated on a hydro-volcanically-active C-class asteroid, probably Ceres [3-7]. We have begun a detailed analysis of the included solids and organics and are re-examining the related carbonaceous (C)) chondrite clast we previously reported in Zag [5-7]. These new investigations will potentially reveal the mineralogy of asteroid Ceres. We report here on potentially identical C chondrite clasts in the H chondrite regolith breccias Tsukuba (H5-6) and Carancas (H4-5). The clast in Tsukuba was known before [8], but the Carancas clast is newly recognized.

Zolensky, M. E.↗
NASA NTRS2017

What Hayabusa2 Will Find at Asteroid Ryugu, and What It Will Reveal About the Source of Earth's Water

Water-rich carbonaceous chondrites contain evidence of aqueous alteration in the early solar system. To see this one must look carefully at the meteorites, and see past the later alteration which has generally obscured mineral textures. We suggest that these materials will dominate, be detectable, and be sampled on the surfaces of C-class asteroids, initially by the Hayabusa2 spacecraft. Thus, hydrous samples returned by this mission will help to reveal the source of water on earth.

Zolensky, Michael↗
NASA NTRS2018

What Hayabusa2 Will Find at Asteroid Ryugu, and What It Will Reveal About the Source of Earth's Water

Water-rich carbonaceous chondrites contain evidence of aqueous alteration in the early solar system. To see this one must look carefully at the meteorites, and see past the later alteration which has generally obscured mineral textures. We suggest that these materials will dominate, be detectable, and be sampled on the surfaces of C-class asteroids, initially by the Hayabusa2 spacecraft. Thus, hydrous samples returned by this mission will help to reveal the source of water on earth.

Zolensky, Michael↗
NASA NTRS2013

Solar Flare X-Ray Source Motion as a Response to Electron Spectral Hardening

Context. Solar flare hard X-rays (HXRs) are thought to be produced by nonthermal coronal electrons stopping in the chromosphere, or remaining trapped in the corona. The collisional thick target model (CTTM) predicts that more energetic electrons penetrate to greater column depths along the flare loop. This requires that sources produced by harder power-law injection spectra should appear further down the legs or footpoints of a flareloop. Therefore, the frequently observed hardening of the injected power-law electron spectrum during flare onset should be concurrent with a descending hard X-ray source. Aims. To test this implication of the CTTM by comparing its predicted HXR source locations with those derived from observations of a solar flare which exhibits a nonthermally-dominated spectrum before the peak in HXRs, known as an early impulsive event. Methods. HXR images and spectra of an early impulsive C-class flare were obtained using the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). Images were reconstructed to produce HXR source height evolutions for three energy bands. Spatially-integrated spectral analysis was performed to isolate nonthermal emission, and to determine the power-law index of the electron injection spectrum. The observed height-time evolutions were then fit with CTTM-based simulated heights for each energy, using the electron spectral indices derived from the RHESSI spectra. Results. The flare emission was found to be dominantly nonthermal above approx. 7 keV, with emission of thermal and nonthermal X-rays likely to be simultaneously observable below that energy. The density structure required for a good match between model and observed source heights agreed with previous studies of flare loop densities. Conclusions. The CTTM has been used to produce a descent of model HXR source heights that compares well with observations of this event. Based on this interpretation, downward motion of nonthermal sources should indeed occur in any flare where there is spectral hardening in the electron distribution during a flare. However, this would often be masked by thermal emission associated with flare plasma pre-heating. As yet, flare models that predict transfer of energy from the corona to the chromosphere by means other than a flux of nonthermal electrons do not predict this observed source descent. Therefore, flares such as this will be key in explaining this elusive energy transfer process.

X-rays↗
NASA NTRSDate not supplied

Outer Solar System Carbon in the Laboratory

Samples of outer solar system carbon in various forms are available for analysis in the laboratory. The Stardust Mission returned organics and a few carbonate grains from Jupiter Class comet Wild-2 [1]. These complement similar phases available in chondritic interplanetary dust particles, some of which derive from comets, although it is not definitively known which have that origin. Carbonaceous chondrites probably derive from C-complex asteroids which may have outer solar system origins, though this origin is model dependent. There are rare carbonaceous xenoliths in, principally, ordinary chondrites and ureilites whose bulk isotopic and bulk chemical compositions suggest an origin farther from the Sun that the remainder of carbonaceous chondrites [2,3]. These contain abundant carbonaceous materials, including organic-bearing aqueous fluid inclusions [4]. The Hayabusa2 spacecraft recently returned samples of C-class asteroid Ryugu to Earth, now being analyzed in labs worldwide. These materials are expected to be dominated by materials similar to C1 and C2 carbonaceous chondrites [5].

Michael Zolensky↗
NASA NTRSDate not supplied

Breakout Reconnection and Eruption in a Double Null-point Topology

Basic Question: Why are some eruptions successful while others remain confined? • We analyzed an eruption associated with a C-class flare in a null-point topology (fan-spine/embedded bipole configuration) within NOAA AR 11791, embedded within a large pseudostreamer between two coronal holes. • About 4 hours prior, interchange reconnection at the null produced a faint jet and a B-class flare without any filament eruption. • Continued reconnection below the filament built a flux rope (FR) that rose slowly and later generated the C1.4 flare. The flux rope reconnected with pseudostreamer flux near inner null, producing a remote (third) ribbon at the base of the fan and partial ejection of the flux rope. • Multiple plasmoids appeared in two places: above the rising flux rope in the breakout current sheet (the deformed null), and in a vertical flare current sheet below the flux rope (quasiperiodic flare reconnection). • Weak, narrow, coronal and interplanetary Type-III radio bursts were also detected, suggesting that electron beams from the null were ejected into the heliosphere. • The partial FR ejected from the inner system encountered the overlying arcade and null of the big pseudostreamer higher in the corona and oscillated, but did not escape. • EUV and coronagraph images revealed a wave and a faint ejection from the pseudostreamer that propagated laterally southward with ~270 km s-1. • We suggest that the main factors leading to the confined filament eruption are (i) lack of significant breakout reconnection between the rising flux rope and the overlying arcade due to an unfavorable relative orientation of these flux systems; and/or (ii) insufficient free energy of the flux rope to overcome the tension forces of the overlying arcades.

J Karpen↗