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At least 1,585 records · Page 88
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NASA NTRS2018

The Volatile Composition of Comet C/2017 E4 (Lovejoy) before its Disruption, as Revealed by High-Resolution Infrared Spectroscopy with iSHELL at the NASA/IRTF

In 2017 April, we acquired comprehensive high-resolution spectra of newly discovered comet C/2017 E4 (Lovejoy) as it approached perihelion, and before its disintegration. We detected many cometary emission lines in the range (2.8-5.3) μm, in four customized instrument settings (L1-c, L3, Lp1-c, and M1) of iSHELL-the new near-IR high-resolution immersion echelle spectrograph at NASA/IRTF (Maunakea, Hawaii). We identified 12 molecular species: nine primary volatiles (H2O, HCN, NH3, CO, C2H2, C2H6, CH4, CH3OH, H2CO) and three product species (CN, NH2, OH). We detected 85 H2O emission lines from 12 water vibrational bands across L1-c and M1 settings. The many detected water emission lines enabled retrieval of accurate measures for ortho- and para-H2O independently, thereby reducing systematic uncertainty in the derived ortho-para ratio and nuclear spin temperature. Excitation analyses and emission profile analyses were performed for all species, and molecular abundance ratios relative to water are compared with values found for other Oort Cloud comets in our infrared database. Abundance ratios are consistent for most species, with the exception of underabundant methanol and overabundant ammonia in E4.

Faggi, S.↗
NASA NTRS2018

The Diversity of Refractory Organic Material in Comets

Organic matter exists in comets (most notably in 81P/Wild 2 [Stardust], 67P/Churyomov- Gerasimenko (67P/C-G) [Rosetta], chondritic porous IDPS, and UCAMMs) and in primitive carbonaceous chondrites that likely retain some chemistry that reflects an origin in the prenatal cold molecular cloud (Alexander+2017). Heavy isotopic enrichments, 15N/14N and possibly D/H, signify preserved molecular cloud organics. In the cold outer disk, if grains are lofted above the disk mid-plane then organics likely experience significant UV processing (Ciesla+2012). In remote sensing of comet comae, organics in the dust are considered refractory or semirefractory. Semi-refractory organics have limited comae lifetimes and produce distributed sources of molecules (H2CO and CO). Rosetta's close passes of 67P/C-G's nucleus (10-15 km) reveals a distributed source of glycine, methyl amine and ethylamine (Altwegg+2016). Cometary samples and primitive meteorites have two types of organic matter: (1) acid-insoluble organic matter (IOM), which is a macromolecular polymer with a mixture of aromatic and aliphatic moieties, and (2) labile, soluble organics, which includes the amino acids, such as glycine (Stardust, Elsila+2009). Meteoritic IOM is robust, withstanding experimental temperatures of 1200 K (Dobrica+2011, Cody+2008). Nanoglobules are a type of IOM; they have a distinct physical structure, but often share the same chemistry as the other IOM from the same meteorite. Moderate-sized PAHs (20 C-atoms) are detected in Stardust samples (Clemett+2010). Refractory organic IOM is ubiquitous yet has a great diversity of abundances between cometary samples. IOM is in primitive chondrites, 67P/C-G (Rosetta), 81P/Wild 2 (Stardust), 1P/Halley, 26P/Grigg-Skjellerup, UCAMMs, anhydrous IDPs, and in chondritic porous IDPs (CP IDPs) and larger cluster IDPs (e.g., Fray+2016, Fomenkova+94, Busemann+ 09, Dobrica+2011, Dobrica+2012). 81P's refractory organic matter is of two types (De Gregorio+2011): nanoglobules of highly aromatic refractory organic matter and polyaromatic carbonyl-containing organic matter, which is similar to IOM in primitive meteorites and IDPs. Fray+2017 estimate that 50% of carbon in 67P/C-G is in IOM. 67P/C-G's organics appear to lack the soluble organic matter, aliphatic carbon, amino acids, and PAHs (Fray+2016). Other notable aspects of the diversity in IOM in cometary samples are the ranges of atomic ratios of N/C, O/C, and H/C, and the range of isotopic enrichments of 15N/14N and D/H. Aqueous and thermal processing on asteroids changes the balance of soluble to insoluble organics, and may be important for diversifying the range of OM delivered to Earth.

Wooden, Diane↗
NASA NTRS2017

BiBlade Sampling Tool Validation for Comet Surface Environments

The BiBlade sampling chain was developed for use in a potential Comet Surface Sample Return mission. Following prior versions of the sampling tool, a new tool was developed and validated to TRL 6. Sample acquisition testing was performed across a range of comet simulants and operational conditions. Tool operation was validated in a thermal-vacuum chamber. The end-to-end sampling chain was validated including sampling, sample measurement, and sample transfer. The sampling system is now ready for flight implementation.

Backes, Paul↗
NASA NTRS2018

The Volatile Composition of Comet C/2017 E4 (Lovejoy) Before Its Disruption, as Revealed by High-Resolution Infrared Spectroscopy with iSHELL at the NASA-IRTF

In April 2017, we acquired comprehensive high-resolution spectra of newly-discovered comet C/2017 E4 (Lovejoy) as it approached perihelion, and before its disintegration. We detected many cometary emission lines in the (2.8–5.3)μm range, in four customized instrument settings (L1-c, L3, Lp1-cand M1) of iSHELL -the new near-IR high resolution immersion echelle spectrograph at NASA/IRTF (Maunakea, Hawaii). We identified twelve molecular species; nine primary volatiles (H2O, HCN, NH3, CO, C2H2, C2H6, CH4, CH3OH, H2CO) and three product species (CN, NH2,OH). We detected 85H2O emission lines from 12 water vibrational bands across L1-c and M1 settings. The many detected water emission lines enabled retrieval of accurate measures for ortho-and para-H2O independently, thereby reducing systematic uncertainty in the derived ortho-para ratio and nuclear spin temperature. Excitation analyses and emission profile analyses were performed for all species, and molecular abundance ratios relative to water are compared with values found for other Oort Cloud comets in our infrared database. Abundance ratios are consistent for most species, with the exception of under-abundant methanol and over-abundant ammonia in E4.

S. Faggi↗
NASA NTRS2000

Ion propulsion system design for the Comet Nucleus Sample Return mission

One of the first science missions to use solar electric propulsion (SEP) may be the Comet Nucleus Sample Return (CNSR) mission which is designed to return samples of volatiles and dust from the nucleus of a comet. The use of SEP for CNSR makes the mission affordable and scientifically more attractive because it enables the use of a smaller, lower cost launch vehicle and it significantly reduces the time required to return samples to the Earth.

CNSR↗
NASA NTRS1995

Changes in Jupiter's 13-cm Synchrotron Radio Emission Following the Impact of Comet Shoemaker-Levy-9

Results of an observing program to monitor the synchrotron radio emission from Jupiter's inner radiation belts before, during and after the impact of Comet SL-9 are reported. The observations were made at 2295 MHz as part of the NASA-JPL Jupiter Patrol, a long-term radio astronomy monitoring program begun in 1971. The data indicate that the intensity of the synchrotron emission at 13 cm wavelength increased by 27 percent within a few days after the comet impacts; the longitudinal beaming curve was distorted during the week of impacts; the magnetic latitude beaming curves flattened after the week of impacts suggesting an increase in the emission at higher magnetic latitudes; and the decay of the enhanced emission is consistent with an exponential with a time constant of ~125 days. The reported changes following the SL-9 impact are unprecedented in the 23-year history of the Jupiter Patrol.

Synchrotron↗
NASA NTRS2018

A Submm-Wave Comet Explorer for Water Isotopic Composition Measurements

Remote submm-wave spectrometers have the capability of providing statistically significant numbers of isotopic composition measurements within the budget constraints of available planetary missions. This talk will present a mission and instrument concept that would enable an accurate measurement of the D/H ratio on not one but several dozens of comets in a four-year mission lifetime. The instrument would utilize advanced cryogenic detectors that would allow us to measure the abundance of the para and ortho spin states of water and its isotopologues. State of the art superconducting heterodyne receivers have been developed that provide detection sensitivities approaching the quantum limit in the 500 GHz frequency range enabling the measurement of D/H ratio on around 50 comets from an observatory stationed for example at the thermally benign Lagrange point L2.

Feldman, Sabrina↗
NASA NTRS2021

Testing Short-term Variability and Sampling of Primary Volatiles in Comet 46P/Wirtanen

The exceptionally favorable close approach of Jupiter-family comet 46P/Wirtanen in 2018 December enabled characterization of its primary volatile composition with exceptionally high spatial resolution and sensitivities using the iSHELL spectrograph at the NASA Infrared Telescope Facility on Maunakea, HI. We sampled emissions from H2O, HCN, C2H2, NH3,C2H6, and CH3OH on UT 2018 December 21 using two instrumental settings that spanned the 2.9–3.6μm spectral region. We also obtained a sensitive 3σupper limit for H2CO and for the rarely studied molecule HC3N. We report rotational temperatures, production rates, and mixing ratios(relative to H2O as well as to C2H6). We place our results in context by comparing them with other comets observed at near-IR wavelengths. We also compare our results with those obtained using the NIRSPEC-2 spectrograph on Keck II on UT December 17 and 18 and with results obtained from iSHELL on other dates during the same apparition. Within1–2σ uncertainty, production rates obtained for all molecules in this work were consistent with those obtained using NIRSPEC-2 except H2O, indicating low-level variability on a timescale of days. Mixing ratios with respect to H2O in 46P/Wirtanen were consistent with corresponding values from NIRSPEC-2 within the uncertainty with the exception of CH3OH, which yielded a higher ratio on December 21. Our measurements afforded a high temporal resolution that spanned∼2/3 of the rotational period of 46P/Wirtanen, enabling us to test short-term variability in the production rates of H2O and HCN due to rotational effects. Both H2O and HCN production rates showed similar temporal variability, resulting in nearly constant HCN/H2O

Younas Khan↗
NASA NTRS2021

The Volatile Composition of the Inner Coma of Comet 46P/Wirtanen: Coordinated Observations Using iSHELL at the NASA-IRTF and Keck/NIRSPEC-2

The 2018 perihelion passage of comet 46P/Wirtanen afforded an opportunity to measure the abundances andspatial distributions of coma volatiles in a Jupiter-family comet with exceptional spatial resolution for severalweeks surrounding its closest approach to Earth(Δmin∼0.078 au on UT December 16). We conducted near-infrared spectroscopic observations of 46P/Wirtanen using iSHELL at the NASA Infrared Telescope Facility onUT 2018 December 18 in direct coordination with observations using the newly upgraded NIRSPEC-2 instrumentat the W. M. Keck Observatory, and securely detectedfluorescent emission from CH3OH, C2H6, and H2O. Thiscoordinated campaign utilizing the two premier near-infrared facilities in the northern hemisphere enabled us tosample distinct projections of the coma into the plane of the sky simultaneously, and provided an unprecedentedview into the inner coma of 46P/Wirtanen near closest approach. We report rotational temperatures, productionrates, and abundance ratios(i.e., mixing ratios)for all sampled species and compare our iSHELL results tosimultaneous(or near-simultaneous)measurements taken with NIRSPEC-2. We demonstrate the extraordinarysynergy of coordinated measurements using iSHELL and NIRSPEC-2, and advocate for future cometary studiesthat jointly leverage the capabilities of these two facilities.

Nathaniel X Roth↗
NASA NTRS2021

The Volatile Composition of the Inner Coma of Comet 46P/Wirtanen: Coordinated Observations Using iSHELL at the NASA-IRTF and Keck/NIRSPEC-2

The 2018 perihelion passage of comet 46P/Wirtanen afforded an opportunity to measure the abundances and spatial distributions of coma volatiles in a Jupiter-family comet with exceptional spatial resolution for several weeks surrounding its closest approach to Earth (Δ(min) ~0.078 au on UT December 16). We conducted near-infrared spectroscopic observations of 46P/Wirtanen using iSHELL at the NASA Infrared Telescope Facility on UT 2018 December 18 in direct coordination with observations using the newly upgraded NIRSPEC-2 instrument at the W. M. Keck Observatory, and securely detected fluorescent emission from CH3OH, C2H6, and H2O. This coordinated campaign utilizing the two premier near-infrared facilities in the northern hemisphere enabled us to sample distinct projections of the coma into the plane of the sky simultaneously, and provided an unprecedented view into the inner coma of 46P/Wirtanen near closest approach. We report rotational temperatures, production rates, and abundance ratios (i.e., mixing ratios) for all sampled species and compare our iSHELL results to simultaneous (or near-simultaneous) measurements taken with NIRSPEC-2. We demonstrate the extraordinary synergy of coordinated measurements using iSHELL and NIRSPEC-2, and advocate for future cometary studies that jointly leverage the capabilities of these two facilities.

Nathaniel X. Roth↗
NASA NTRS2022

Oxygen Isotopes of Anhydrous Primary Minerals Show Kinship Between Asteroid Ryugu and Comet 81P/Wild2

The extraterrestrial materials returned from asteroid (162173) Ryugu consist predominantly of low-temperature aqueously formed secondary minerals and are chemically and mineralogically similar to CI (Ivuna-type) carbonaceous chondrites. Here we show that high-temperature anhydrous primary minerals in Ryugu and CI chondrites exhibit a bimodal distribution of oxygen isotopic compositions: 16 O-rich (associated with refractory inclusions) and 16 O-poor (associated with chondrules). Both the 16 O-rich and 16 O-poor minerals probably formed in the inner solar protoplanetary disk and were subsequently transported outwards. The abundance ratios of the 16 O-rich to 16 O-poor minerals in Ryugu and CI chondrites are higher than in other carbonaceous chondrite groups, but are similar to that of comet 81P/Wild2, suggesting that Ryugu and CI chondrites accreted in the outer Solar System closer to the accretion region of comets.

Noriyuki Kawasaki↗
NASA NTRS2014

Badger COMET Compartmentalized Onboard Material Extrusion Technology

In response to the 2014 NASA Academic Innovation Challenge, the University of Wisconsin – Madison team presents the design of a collapsible Fused Deposition Modeling (FDM) system for in situ manufacturing in a space habitat environment, the Badger Compartmentalized Onboard Material Extrusion Technology (COMET). The proposed mechanism incorporates one year of design and testing on an array of current additive manufacturing techniques, with the goal of providing a reliable and maintainable manufacturing solution. Seven Level 1 requirements were employed to guide the design process, based on information in the challenge, communications with NASA, and the evolving systems feedback of project work groups. These requirements provided a baseline for the development of the System Requirements Document (SRD, Appendix I), which framed the design of the system. The design requirements deemed critical to the success of the systems are as follows: - The system shall compose an FDM workstation capable of producing parts within industry standard tolerances. - The system shall reduce to a minimum of 50 percent or less of its deployed volume when not in use, and must collapse without the need for disassembly. - The system shall meet all relevant NASA safety and functional standards. The final design for the Badger COMET was selected from multiple design iterations, which balanced the critical design requirements listed above with system reliability, with the final goal of providing a minimal system weight. The system collapses in the vertical direction, allowing for a maximum reduction in volume. Guide rods and precision, anti-backlash lead screws provide all linear movement in the device. Stepper motors were chosen to actuate each system axis, due to their high precision and repeatable accuracy. The system is controlled through an on-board computer system and embedded electronics package.

Frederick T. Elder↗
NASA NTRS2026

The Evolution in Coma Molecular Composition of Comet C/2017 K2 (PanSTARRS) Across the H 2 O Sublimation Zone: ALMA Imaging of an H 2 O-Dominated Coma

We report a survey of molecular emission from cometary volatiles using the Atacama Large Millimeter/Submillimeter Array (ALMA) toward comet C/2017 K2 (PanSTARRS) carried out on UT 2022 September 21, 22, and 23 at a heliocentric distance r H 3 OH, and H 2 CO (along with continuum emission from dust) sampled molecular chemistry in C/2017 K2 at the inner edge of the H 2 O sublimation zone, the region from r H 2 O begins vigorously subliming and increasingly dominating comet activity, discerning parent from daughter or extended source species. This work presents spectrally integrated flux maps, production rates, and parent scale lengths for each molecule. CH 3 OH, CO, and HCN were produced within ~250 km of the nucleus, potentially including contributions from sublimation of icy grains. CS was consistent with production from CS 2 photolysis, and H 2 CO required production from extended sources in the coma. An ortho-to-para ratio of 2.9 ± 0.4 for H 2 CO was derived from simultaneously measured transitions of each spin species. The continuum was extended and spatially resolved, consistent with thermal emission from dust in the coma. Analysis of the continuum visibilities provided an upper limit on the nucleus diameter d <6.6 km and coma dust masses of (1.2-2.4) times10 11 kg.

Nathan X Roth↗
DOE OSTI2018

Experiment Design with Confidence: CoMET

The Nuclear Science User Facilities (NSUF) has been facilitating nuclear materials research since 2007 by providing access to national laboratory and other partner capabilities at no cost to the researchers. With funding from the Department of Energy – Office of Nuclear Energy, approximately 400 projects have been awarded to support research into radiation effects on fuels and materials. During these ten years, the NSUF has created tools to help researchers write better proposals and perform better research projects. In 2018, several of those tools have been combined to create a single point of access to NSUF information management resources. The Combined Materials Experiment Toolkit or CoMET, combines the Nuclear Energy Infrastructure Database (NEID), the Nuclear Fuels and Materials Library (NFML), and the NSUF proposal system, with a new subject matter expert database and an experiment design tool. The NEID contains information on 500 nuclear R&D facilities around the world, including 85 NSUF partner facilities. The NFML has information on nearly 10,000 material specimens, mostly irradiated materials, which can be used for research in NSUF projects. The new SME database includes contact information for NSUF researchers and scientists. The experiment design tool is an expert system that can guide a researcher through the process of designing an NSUF project by interacting with the other resources. Once a researcher has worked through this process, they will be able to save their experiment plan and input it into the NSUF proposal system. These tools are intended to aid both new and veteran researchers build solid research projects and take full advantage of NSUF resources. They also help the NSUF administer the hundreds of proposals that it receives each year. In the future, NSUF plans to add integrated data storage and retrieval to CoMET.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1998

A Double Nucleus of Comet Evans-Drinkwater (C/1996 J1)

The nucleus of comet C/1996 J1, whose duplicity was first detected in early May 1997, ~4 months after perihelion, is found to have split nontidally ~70 days before perihelion at 1.65 AU from the Sun.

comet Evans-Drinkwater double nucleus nontidal spl↗