Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “ISM”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

NASA’s In-Space Manufacturing Project: Update on Manufacturing Technologies and Materials to Enable More Sustainable and Safer Exploration

NASA’s In-Space Manufacturing (ISM) project seeks to develop the materials, processes, and manufacturing technologies needed to provide an on-demand manufacturing capability for deep space exploration missions. The ability to manufacture and recycle some parts on demand rather than launch them from earth has the potential to reduce logistics requirements on long duration missions and enhance crew safety. With the launch of the first 3D printer (built and operated by Made in Space through a Small Business Innovative Research – SBIR -- contract) to the International Space Station (ISS) in 2014, the ISM project demonstrated the feasibility of operating an on-demand manufacturing system in a microgravity environment. This paper will provide an update on recent advancements in ISM under three key technology areas: manufacturing, recycling, and development of a design database. ISM continues to pursue development of manufacturing technologies for space applications and use the ISS as a critical test bed to prove out these technologies before deploying them on next generation exploration systems. Activities under this focus area include: characterization of materials manufactured using the Additive Manufacturing Facility (AMF), the second generation commercial 3D-printer on ISS, also owned and operated by Made in Space; development of prototype payloads for metal manufacturing through phase II SBIR contracts with Tethers Unlimited, Made in Space, and Ultra Tech Machinery; development of a multi-material fabrication laboratory capable of processing metals and providing inspection of manufactured parts through a Broad Agency Announcement (Techshot, Interlog, and Tethers Unlimited); an in-line sensing system for ISM platforms; and development of higher strength feedstocks for 3D polymer printers. In the area of recycling, the Tethers Unlimited Refabricator payload (an integrated 3D printer and recycler for ULTEM 9085) launched to ISS in November 2018 and began operating in early 2019. This payload represents the first demonstration of on-orbit recycling; down massed specimens will assess material degradation in the polymer over multiple recycling cycles to define limits on material re-use. Other work in the recycling area includes development of common use materials intended to be reused and recycled on space missions (Tethers Unlimited and Cornerstone Research Group) and a sterilization capability for multiple-use materials (ERASMUS from Tethers Unlimited). Concurrent with manufacturing technology and materials development work is creation of a design database, a curated list of parts that can be manufactured using the suite of In-Space Manufacturing capabilities.

Tracie Prater↗
NASA NTRSDate not supplied

Formation of Complex Organic Molecules (COMs) from Polycyclic Aromatic Hydrocarbons (PAHs): Top-Down Synthesis of organics in planetary systems

Complex, organic molecules have been found in many solar system objects (i.e., dust, comets, meteorites, moons, etc.); however, their origins and formation remain a mystery. Two chemical evolutionary pathways have been proposed to explain the organic inventory of our solar system. The first pathway, the top-down approach, suggests an interstellar (ISM) heritage whereby the organic material found in the solar system formed from the erosion and functionalization of large pre-solar carbon-bearing species (mainly large Polycyclic Aromatic Hydrocarbons or PAHs). The second pathway suggests that the origin of the Solar System prebiotic matter is the result of bottom-up synthesis from small reactive molecules (e.g., formaldehyde – H2CO, acetylene – H2C2, and similar species). In this second scenario, it is supposed that very few, if any, pre-solar large molecules could have survived due to the proto - solar nebula radiation environment. Polycyclic Aromatic Hydrocarbons or PAHs comprise ~20-30% of all available carbon in the Universe. The PAHs found within our Solar System tend to be smaller than those suspected to be in the ISM, comprised of only 14 to 18 carbon atoms in size whereas ISM PAHs are typically 50 to 100 carbon atoms. The disparity in PAH sizes between the ISM and Solar System environments is not understood, but may point to conversion of large ISM PAHs to Solar System Organics. This presentation details recent experiments regarding the stability of large PAHs to the various types of radiation found within a proto - solar disk and the production of smaller, complex, molecules from the degradation of the larger PAHs. The presentation will highlight differences and similarities in degradation products based on experimental conditions (e.g., radiation type) and discuss future work with a new experimental setup known as ICEE (Institute for Carbon Evolution Experiments).

molecukes↗
NASA NTRS1982

The effects of ejecta on the X-ray luminosities of supernova remnants

Because X-ray luminosities of most SNRs are dominated by emission from heavy elements, estimates of the X-ray emitting mass based on cosmic abundances may be incorrect. Here we investigate the apparent density evolution of a SNR when substantial amounts of processed material are ejected by the supernova. If this material is shock heated, it will dominate X-ray emission from the remnant long after the SNR has swept up the equivalent amount of interstellar matter (ISM). Emission from metal-rich ejecta may explain why ISM densities of young remnants far from the galactic plane, deduced from standard analysis, are higher than expected, as well as why larger SNRs appear to be lying in regions of lower ISM density. It should be included in detailed calculations of SNR surface brightness distributions, along with effects due to departures from ionization equilibrium and cloudlet evaporation in a multiphase ISM which may also contribute to the apparent evolution of density with radius.

Long, K. S.↗
NASA NTRS1985

Electron capture decay of cosmic rays: A model of the inhomogeneous interstellar medium

Traditional analyses of cosmic ray composition seek to identify the sources through a determination of a the isotopic abundances of these nuclei prior to acceleration. At the same time, it is both necessary and interesting to understand the nature of the medium through which cosmic rays pass before arriving at detectors. In fact, only within a model of the interstellar medium (ISM) sampled by cosmic rays can a refined estimate of source composition be made. An elaboration of the traditional model of the ISM used in studying cosmic ray propagation is explored. Inhomogeneity of the ISM is accomodated in this model. Within this model it is found that the abundances of some electron apture isotopes, are very sensitive to density inhomogeneities which might be expected in the ISM. These nuclei therefore measure the penetration of heavy cosmic rays into interstellar clouds.

Letaw, J. R.↗
NASA NTRS1984

X-ray emission from supernova remnants MSH 14 - 63 and RCW 103

Electron-ion collisions, heavy element enrichment of emissions from reverse-shocked ejecta, abundances in the interstellar medium (ISM), the correspondence between the projected and measured age, ISM particle density, and distance, and classification factors for Type I or II supernovae are examined using a nonequilibrium ionization (NEI) model. The NEI model accounts for the absence of collisional ionization equilibrium and possibly thermal equilibrium between electrons and ions behind the shock fronts, and describes the emission spectra from ejecta and the shocked ISM. When applied to data from the SNR MSH 14 - 63 a non-Coulomb, ion-electron interaction is obtained that is consistent with a shocked ISM. For the SNR RCW 103, however, the processes behind the shock front are not discernable, although the elemental abundances will have solar values if the interactions are non-Coulomb. The age of RCW 103 must be approximated from physical data, as Chinese astronomers would not have been able to see the event from their position on earth two millenia ago.

Nugent, J. J.↗
NASA NTRS1987

The C-12/C-13 isotope ratio of the interstellar medium in the neighborhood of the sun

Data from observations of Xi Per, P Cyg, 20 Tau, and 23 Tau, obtained at 4232 and 3957 A using a coude spectrograph and a 1872-element reticon on the 3-m Shane telescope at Lick Observatory during 1984-1985, are combined with data on Zeta Oph (Hawkins et al., 1985) and used to estimate the C isotope ratio of the ISM near the sun. The results are presented in extensive tables and graphs and characterized in detail. The (C-12)H(+)/(C-13)H(+) abundance ratios toward the five stars are found to agree to within 12 percent and shown to be representative of the C-12/C-13 ratios in the gas, strongly indicating that the local ISM is homogeneous. The difference between the ISM ratio (43 + or - 4) and the solar-system value (89) is attributed to the chemical evolution of the ISM in the 4.9 Gyr since the formation of the sun.

Hawkins, Isabel↗
NASA NTRS1989

Stochastic histories of dust grains in the interstellar medium

The purpose is to study an evolving system of refractory dust grains within the Interstellar Medium (ISM). This is done via a combination of Monte Carlo processes and a system of partial differential equations, where refractory dust grains formed within supernova remnants and ejecta from high mass loss stars are subjected to the processes of sputtering and collisional fragmentation in the diffuse media and accretion within the cold molecular clouds. In order to record chemical detail, the authors take each new particle to consist of a superrefractory core plus a more massive refractory mantle. The particles are allowed to transfer to and fro between the different phases of the interstellar medium (ISM) - on a time scale of 10(exp 8) years - until either the particles are destroyed or the program finishes at a Galaxy time of 6x10(exp 9) years. The resulting chemical and size spectrum(s) are then applied to various astrophysical problems with the following results. For an ISM which has no collisional fragmentation of the dust grains, roughly 10 percent by mass of the most refractory material survives the rigors of the ISM intact, which leaves open the possibility that fossilized isotopically anomalous material may have been present within the primordial solar nebula. Stuctured or layered refractory dust grains within the model cannot explain the observed interstellar depletions of refractory material. Fragmentation due to grain-grain collisions in the diffuse phase plus the accretion of material in the molecular cloud phase can under certain circumstances cause a bimodal distribution in grain size.

Liffman, Kurt↗
NASA NTRS1993

Static galactic halo and galactic wind

Although the exact state of the interstellar medium (ISM) in our Galaxy (other galaxies as well) is not clear at all, the 'common consensus' is that a rough pressure balance (or equipartition of energy) exists between different components and phases: cold, warm, hot phases of the ISM, magnetic field, cosmic rays, etc. If the halo of a galaxy is taken to be an extension of the ISM, then its structure is influenced by various ISM components. A 'complete' description of the halo is evidently very complicated. This paper gives a brief account on cosmic ray halo, which emphasizes the role played by cosmic rays. The interaction between cosmic rays and thermal plasma is facilitated by magnetic field. The cosmic rays are scattered by hydromagnetic waves (e.g., Alfven waves) which in turn can be generated by cosmic ray streaming instability. This constitutes a self-consistent picture. Since we are interested in the structure of the halo, we adopted a hydrodynamic model in which the cosmic rays and waves are described by their pressures. In general there are two classes of halos: static and dynamic.

Ko, Chung-Ming↗
NASA NTRS1993

The morphology and interaction with the interstellar medium of the planetary nebula IC 4593

We present a morphological study of the planetary nebula IC 4593, based on our observations in H-alpha, forbidden O III, and forbidden S II. From the H-alpha intensity map, we calculate densities and masses for constituent structures and for the nebula as a whole. We argue that the morphology of IC 4593 suggests that it is moving supersonically through the ISM, and that the ISM shock may be thermally unstable, oscillating between adiabatic and radiative (isothermal) shock conditions. Spectroscopic observations are necessary to further explore the nature of the interaction between IC 4593 and the ISM. An improved understanding of such interactions will greatly expand the potential use of planetary nebulae to probe the ISM.

Zucker, Daniel B.↗
NASA NTRS1994

The interstellar medium in the starburst regions of NGC 253 and NGC 3256

We discuss observations of the (C II) 158 micrometers, (O I) 63 micrometers, (Si II) 35 micrometers, (O III) 52,88 micrometers, and (S III) 33 micrometers fine-structure transitions toward the central 45 seconds of the starburst galaxies NGC 253 and NGC 3256. The (C II) and (O I) emission probably originates in photodissociated gas at the surfaces of molecular clouds, although a small (less than or approximately 30%) contribution to the (C II) flux from H II regions cannot be ruled out. The (O III) and (S III) lines originate in H II regions and the (Si II) flux is best explained as originating in H II regions with some contribution from photodissociation regions (PDRs). The gas phase silicon abundance is nearly solar in NGC 253, which we interpret as evidence for grain destruction in the starburst region. We find that the photodissociated atomic gas has densities approximately 10(exp 4)/cu cm and temperature 200-300 K. About 2% of the gas is in this phase. The thermal gas pressure in the PDRs, P(PDR)/k approximately 1-3 x 10(exp 6) K/cu cm, might represent the 'typical' interstellar gas pressure in starburst systems. The Far Ultraviolet (FUV) radiation fields illuminating the clouds are 10(exp 3)-10(exp 4) stronger than the local Galactic FUV field and come from the contribution of many closely packed O and B stars. For the central 250 pc of NGC 253, we find that the H II gas has an average density n(sub e) is approximately 400/cu cm. This corresponds to a thermal pressure P(H II)/k approximately 7 x 10(exp 6) K/cu cm which is approximately P(PDR)/k, suggesting that the ionized gas is in pressure equilibrium with the photodissociated gas at the surfaces of molecular clouds. The H II gas fills a significant fraction, approximately 0.01-0.3, of the volume between the clouds. The effective temperature of the ionizing stars in NGC 253 is greater than or approximately 34,500 K; 2 x 10(exp 5) O7.5 stars would produce the observed Lyman countinuum photon luminosity. The average separation between the stars is approximately 3 pc. Applying the simple model for the interstellar medium in galactic nuclei of Wolfire, Tielens, & Hollenbach (1990), we find the molecular gas in the central regions of NGC 253 and NGC 3256 to be distributed in a large number (5 x 10(exp 3) to 5 x 10(exp 5)) of small (0.5-2 pc), dense (approximately 10(exp 4)/cu cm) clouds (or alternatively 'thin-flattened' structures) with volume filling factors 10(exp -3) to 10(exp -2), very different from the local Interstellar Medium (ISM) of the Galaxy. We suggest a self-consistent scenario for the ISM in NGC 253 in which clouds and H II gas are in pressure balance with a supernova-shocked, hot 1-3 x 10(exp 6) K, low-density (approximately 10(exp 4)/cu cm), all pervasive medium. A feedback mechanism may be indicated in which the pressure generated by the supernovae compresses the molecular clouds and triggers further massive star formation. The similarity of ISM parameters deduced for NGC 253, NGC 3256, and M82 (Lord et al. 1993) suggests that the ISM properties are independent of the luminosity of the starburst or the triggering mechanism, but are rather endemic to starburst systems. The starburst in NGC 3256 appears to be a scaled-up version of the NGC 253 and M82 starbursts.

Carral, P.↗
NASA NTRS1994

Asymptotic Giant Branch stars as a source of short-lived radioactive nuclei in the solar nebula

We carried out a theoretical evaluation of the contribution of Asymptotic Giant Branch (AGB) stars to some short-lived (10(exp 6) less than or equal to Tau-bar less than or equal to 2 x 10(exp 7) yr) isotopes in the Interstellar Medium (ISM) and in the early solar system using stellar model calculations for thermally pulsing evolutionary phases of low-mass stars. The yields of s-process nuclei in the convective He-shell for different neutron exposures tau(sub 0) were obtained, and AGB stars were shown to produce several radioactive nuclei (especially Pd-107, Pb-205, Fe-60, Zr-93, Tc-99, Cs-135, and Hf-182) in diferent amounts. Assuming either contamination of the solar nebula from a single AGB star or models for continuous injection and mixing from many stars into the ISM, we calculate the ratios of radioactive to stable nuclei at the epoch of the Sun's formation. The dilution factor between the AGB ejecta and the early solar system matter is obtained by matching the observed Pd-107/Pd-108 and depends on the value of tau(sub 0). It is found that small masses M(sub He) of He-shell material (10(exp -4)-10(exp -7) solar mass) enriched in s-process nuclei are sufficient to contaminate 1 solar mass of the ISM to produce the Pd-107 found in the early solar system. Predictions are made for all of the other radioactive isotopes. The optimal model to explain several observed radioactive species at different states of the proto-solar nebula involves a single AGB star with a low neutron exposure (tau(sub 0) = 0.03 mbarn(sup -1)) which contaminated the cloud with a dilution factor of M(sub He)/solar mass approximately 1.5 x 10(exp -4). This will also contribute newly synthesized stable s-process nuclei in the amount of approximately 10(exp -4) of their abundances already present in the proto-solar cloud. Variations in the degree of homogenization (approximately 30%) of the injected material may account for some of the small general isotopic anomalies found in meteorites. It is also found that Fe-60 is produced in small but significant quantities that may be sufficient to explain the observations if the time elapsed delta from the contamination of the ISM to the formation of protoplanetary bodies is not higher than delta = 5 x 10(exp 6) yr. If delta is longer, up to 10 x 10(exp 6) yr, this would require the single AGB star to experience enhanced neutron densities (n(sub n) approximately 3 x 10(exp 9)n/cu cm) in the s-processing zone in order to compensate for the branching at Fe-59. The alternative model of long-term continuous ejection of matter from many AGB stars does not appear to match the observations. We also estimate the Al-26 production from the H-shell and find that the Al-26 abundance in the early solar system may be readily explained in a self-consistent manner. Moreover, Al-26 from AGB stars may contribute substantially to the galactic Al-26 gamma-source, while no significant gamma-flux from Co-60 (deriving from Fe-60 decay) is to be expected.

Wasserburg, G. J.↗
NASA NTRS1994

Interstellar gas and dust in the young cluster IC 348

We have completed a multiband absorption- and emission-line study of a star embedded in the young cluster IC 348, to determine the environmental effect of star formation on the interstellar medium (ISM) local to the region. The hottest and youngest star in IC 348 is BD +31 deg 643, a B5 V star which samples the inner bright nebular region. The nearby star omicron Per, which lies only 8 min to the north and is thought to lie beyond IC 348, samples the gas and dust which has not been processed by very recent star formation. We speculate that the ISM throughout the region was originally the same as that currently seen toward omicron Per, but now the constrasting environmental conditions due to the recent star formation have led to marked differences in the atomic, molecular, and dust characteristics of IC 348. These contrasts include what we have termed a 'composite' UV extinction curve for BD +31 deg 643, evidence for enhanced density and enhanced depletions within IC 348 and very different molecular abundances in the interstellar sightline to BD +31 deg 643. Toward BD +31 deg 643, we find a higher column density of CH, but lower CN and very much higher CH(+) than measured toward omicron Per. We conclude that the physical and chemical state of the gas and dust has been altered by local processes and conditions within IC 348. The characteristics of the ISM in IC 348, via our study of the star BD +31 deg 643, closely resembles those seen toward rho Oph, another sight line passing through a bright nebular region. However, the stars are not as hot in IC 348 as in Ophiuchus, so their effect on the local ISM is not as severe.

Snow, Theodore P.↗
NASA NTRS1995

The life cycle of the Interstellar Medium in other galaxies

Gas in spiral galaxies cycles between the diffuse and dense phases as clouds collapse, form stars and are dispersed back into the ISM. Far infrared observations of continuum emission from interstellar dust and line emission from interstellar gas have revealed a wealth of information on the state of the ISM in galaxies of different morphological types. The analysis of these observations gives us information about the processes of star formation and about the evolution of the ISM. Star formation rates vary widely from galaxy to galaxy, with the rates in starburst galaxies being 10 - 100 times those in quiescent spiral galaxies. Far infrared spectroscopy of star-forming galaxies shows that the interstellar pressure increases with star formation rate. The structure of the interstellar medium in starburst galaxies is quite different from that of quiescent galaxies - much of the mass and volume are in HII regions and photodissociation regions. The size distribution of dust grains seems to depend on environment; small grains are abundant in the diffuse interstellar medium but not in dense molecular star forming regions. Quiescent spiral and elliptical galaxies contain a significant population of small grains, but starburst galaxies do not. Dwarf irregular galaxies also seem to contain few small grains; this may be the result of the higher UV flux in these galaxies. The star forming regions in dwarf irregulars also have a higher ratio of atomic to molecular gas than do those in the Galaxy. These results show that the ISM in galaxies of different morphological types reaches different equilibria, resulting in different modes of star formation and global galaxy evolution.

Knapp, G. R.↗
NASA NTRS1998

On the Nature of the High Velocity(26) Al Near the Galactic Center

Recent observations of the Galactic Center region by the GRIS balloon-borne germanium spectrometer have determined that the diffuse 1809 keV emission resulting from the decay of Al-26 has an intrinsic width of 5.4 keV FWHM. This line width indicates that the Al-26 is either at a temperature of approximately 4.5 x 10(exp 8) K or it has a nonthermal velocity of approximately 500 km/s. Previous authors have suggested that the Al-26 must be trapped within dust grains in the ISM in order for these conditions to persist over the 10(exp 6) year lifetime of the aluminum (see e.g. Naya et al. 1996, Chen et al. 1998). We discuss the results of our model for the initial acceleration of the Al-26 in dust grains as they exit their source, Type II supernovae, and their subsequent reacceleration in the ISM by ambient supernova remnant (SNR) shocks. Our results show that dust grains can be maintained at a velocity sufficient to explain the GRIS observation for ISM densities of approximately 0.2 cu cm, dust grain sizes near 10(exp -5) cm, and distances between SNR shocks in the ISM of 100 - 200 pc.

Sturner, Steven J.↗
NASA NTRS1999

Additional Contributions to the Development of the New Snow-Physics Scheme for SSiB

The Simplified Simple Biosphere Model (SSiB) had a well-documented problem with snowmelt timing and infiltration. A new snow-physics scheme was developed for use in SSIB. In this, the snow layer is separated from the soil, with its own energy budget and temperature. Solar energy reaching the top of the snowpack is divided into three parts: one, reflected by the snow; two, absorbed by the snow; and three, transmitted to the ground following a simple extinction relation. Heat is exchanged between the ground and snow by conduction and by radiation through an arbitrary air-gap between them. In the GSWP exercise using the GEWEX ISLSCP Initiative I forcing data (hereafter "offline"), it was found that the new snow scheme ameliorated a significant fraction of snowmelt time-delay as compared to observations from satellite. It also produced warmer ground temperatures under the snowpack, which allowed realistic meltwater infiltration, resulting in better simulated spring soil moisture recharge and peak runoff amount as compared to observations. An ensemble of six June-July-August (JJA) simulations for 1987 and 1988 were performed with the NASA Goddard GEOS II GCM coupled with the new snow-physics SSIB using new initial soil moisture (ISM) from the offline simulations. The GCM produced more realistic precipitation in northern regions that had large snowmelt and wetter ISM in response to better snow-physics, as compared to simulations with ISM without the new snow scheme. The new SSiB-GCM also increased the interannual precipitation signal in the Indian monsoon region, resulting from changes in ISM in the Himalayas and central Asia.

Mocko, David M.↗
NASA NTRS2001

Identifying Organic Molecules in Space: The AstroBiology Explorer (ABE) MIDEX Mission Concept

Infrared spectroscopy in the 2.5-16 micron range is a principle means by which organic compounds are detected and identified in space. Ground-based, airborne, and spaceborne IR spectral studies have already demonstrated that a significant fraction of the carbon in the interstellar medium (ISM) resides in the form of complex organic molecular species. Unfortunately, neither the distribution of these materials nor their genetic and evolutionary relationships with each other or their environments are well understood. The Astrobiology Explorer (ABE) is a MIDEX mission concept currently under study at NASA's Ames Research Center in collaboration with Ball Aerospace and Technologies Corporation. ABE will conduct IR spectroscopic observations to address outstanding important problems in astrobiology, astrochemistry, and astrophysics. The core observational program would make fundamental scientific progress in understanding (1) the evolution of ices and organic matter in dense molecular clouds and young forming stellar systems, (2) the chemical evolution of organic molecules in the ISM as they transition from AGB outflows to planetary nebulae to the general diffuse ISM to H II regions and dense clouds, (3) the distribution of organics in the diffuse ISM, (4) the nature of organics in the Solar System (in comets, asteroids, satellites), and (5) the nature and distribution of organics in local galaxies. The technical considerations of achieving these science objectives in a MIDEX-sized mission will be described.

Sandford, Scott A.↗
NASA NTRS2001

Detecting and Identifying Organic Molecules in Space: The AstroBiology Explorer (ABE) MIDEX Mission Concept

Infrared spectroscopy in the 2.5-16 microns (4000-625/cm) range is a principle means by which organic compounds are detected and identified in space. Ground-based, airborne, and spaceborne IR spectral studies have already demonstrated that a significant fraction of the carbon in the interstellar medium (ISM) resides in the form of complex organic molecular species. Unfortunately, neither the distribution of these materials nor their genetic and evolutionary relationships with each other or their environments are well understood. The Astrobiology Explorer (ABE) is a MIDEX (Medium-class Explorer) mission concept currently under study at NASA's Ames Research Center in collaboration with Ball Aerospace and Technologies Corporation. ABE will conduct IR spectroscopic observations to address outstanding important problems in astrobiology, astrochemistry, and astrophysics. The core observational program would make fundamental scientific progress in understanding (1) the evolution of ices and organic matter in dense molecular clouds and young forming stellar systems, (2) the chemical evolution of organic molecules in the ISM as they transition from AGB outflows to planetary nebulae to the general diffuse ISM to H II regions and dense clouds, (3) the distribution of organics in the diffuse ISM, (4) the nature of organics in the Solar System (in comets, asteroids, satellites), and (5) the nature and distribution of organics in local galaxies. Both the scientific goals of the mission and how they would be achieved will be discussed.

Sandford, Scott A.↗
NASA NTRS2001

The AstroBiology Explorer (ABE) MIDEX Mission Concept: Exploring the Links Between the Interstellar Medium and Meteorites

Infrared spectroscopy in the 2.5-16 micron range is a principle means by which organic compounds can be detected and identified in space via their vibrational transitions. Ground-based, airborne, and spaceborne IR spectral studies have already demonstrated that a significant fraction of the carbon in the interstellar medium (ISM) resides in the form of complex organic molecular species. Furthermore, the presence of D-enriched organics in meteorites suggests that a portion of these materials survives incorporation into protosolar nebulae. Unfortunately, neither the distribution of these materials nor their genetic and evolutionary relationships with each other or their environments are well understood. The Astrobiology Explorer (ABE) is a MIDEX mission concept currently under study at NASA's Ames Research Center in collaboration with Ball Aerospace and Technologies Corporation. ABE will conduct IR spectroscopic observations to address outstanding important problems in astrobiology, astrochemistry, and astrophysics. The core observational program would make fundamental scientific progress in understanding (1) the evolution of ices and organic matter in dense molecular clouds and young forming stellar systems, (2) the chemical evolution of organic molecules in the ISM as they transition from AGB outflows to planetary nebulae to the general diffuse ISM to HII regions and dense clouds, (3) the distribution of organics in the diffuse ISM, (4) the nature of organics in the Solar System (in comets, asteroids, satellites), and (5) the nature and distribution of organics in local galaxies. In addition, ABE will attempt to detect and quantify deuterium enrichments in a select set of these materials and environments. This should assist both with understanding the chemical processes that occur in these environments and with establishing any links that exist between interstellar and meteoritic organics.

Sandford, Scott A.↗