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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

The fossil record of evolution: Data on diversification and extinction

Understanding of the evolution of complex life, and of the roles that changing terrestrial and extraterrestrial environments played in life's history, is dependent upon synthetic knowledge of the fossil record. Paleontologists have been describing fossils for more that two centuries. However, much of this information is dispersed in monographs and journal articles published throughout the world. Over the past several years, this literature was surveyed, and a data base on times of origination and extinction of fossil genera was compiled. The data base, which now holds approximately 32,000 genera, covers all taxonomic groups of marine animals, incorporates the most recent taxonomic assignments, and uses a detailed global time framework that can resolve originations and extinctions to intervals averaging three million years in duration. These data can be used to compile patterns of global biodiversity, measure rates of taxic evolution, and test hypotheses concerning adaptive radiations, mass extinctions, etc. Thus far, considerable effort was devoted to using the data to test the hypothesis of periodicity of mass extinction. Rates of extinction measured from the data base have also been used to calibrate models of evolutionary radiations in marine environments. It was observed that new groups, or clades of animals (i.e., orders and classes) tend to reach appreciable diversity first in nearshore environments and then to radiate in more offshore environments; during decline, these clades may disappear from the nearshore while persisting in offshore, deep water habitats. These observations have led to suggestions that there is something special about stressful or perturbed environments that promotes the evolution of novel kinds of animals that can rapidly replace their predecessors. The numerical model that is being investigated to study this phenomenon treats environments along onshore-offshore gradients as if they were discrete habitats. Other aspects of this investigation are presented.

Sepkoski, J. J., Jr.↗
NASA NTRS1993

Molecular processes in comets

Classical trajectory calculations of the cross sections for vibrational and rotational energy exchange in direct and reactive collisions of hydrogen atoms and hydrogen molecules have been carried out. To test the sensitivity, three potential energy surfaces have been used. For the exchange transitions which occur at small internuclear distances, the rate coefficients for the three surfaces agree quite well. For the direct transitions, there are significant differences for the pure rotational transitions from j=0 to 2 and from j=1 to j=3 in which there is no change in vibration. For higher j the differences tend to disappear, suggesting that the rotational angular momentum can couple to the orbital angular momentum to overcome the centrifugal barrier. Complete numerically exact quantum mechanical calculations for the process in which vJ changes have been performed. Dr. M. A'Hearn has provided data on the fluorescent population of the NH rotational and fine-structure levels from which we should be able to predict accurate photodissociation lifetimes. The distribution rate of C2 is being investigated. A review of H3(+) in terrestrial and extraterrestrial environments was prepared for a volume of Advances in Atomic, Molecular and Optical Physics.

Dalgarno, A.↗
NASA NTRS1993

Establishing a relationship between maximum torque production of isolated joints to simulate EVA ratchet push-pull maneuver: A case study

As manned exploration of space continues, analytical evaluation of human strength characteristics is critical. These extraterrestrial environments will spawn issues of human performance which will impact the designs of tools, work spaces, and space vehicles. Computer modeling is an effective method of correlating human biomechanical and anthropometric data with models of space structures and human work spaces. The aim of this study is to provide biomechanical data from isolated joints to be utilized in a computer modeling system for calculating torque resulting from any upper extremity motions: in this study, the ratchet wrench push-pull operation (a typical extravehicular activity task). Established here are mathematical relationships used to calculate maximum torque production of isolated upper extremity joints. These relationships are a function of joint angle and joint velocity.

Pandya, Abhilash↗
NASA NTRS1993

On the isolation of halophilic microorganisms from salt deposits of great geological age

From salt sediments of Triassic or Permian age from various locations in the world halophilic microorganisms were isolated. Molecular characteristics of several of the isolates suggested they belong to the archaebacteria. One group appears to represent novel strains; several properties of one such isolate, strain BIp, are described here. The existence of viable microorganisms in ancient sediment would have great implications with respect to our notions on evolution, the research for life in extraterrestrial environments, and the longterm survival of functional biological structures. Of crucial importance is thus the question if these microorganisms existed in the salt since the time of deposition or invaded at some later date. Some suggestions to address these issues experimentally are discussed.

Stan-Lotter, Helga↗
NASA NTRS1993

On the Isolation of Halophilic Microorganisms from Salt Deposits of Great Geological Age

From salt sediments of Triassic or Permian ace from various locations in the world halophilic microorganisms were isolated. Molecular characteristics of several of the isolates suggested they belong to the archaebacteriae. One group appears to represent novel strains; several properties or one such isolate, strain BIp, are described here. The existence of viable microorganisms in ancient sediments would have great implications with respect to our notions on evolution, the search for life in extraterrestrial environments and the long- term survival of functional biological structures. Of crucial importance is thus the question if these microorganisms existed in the salt since the time of deposition or invaded at some later date. Some suggestions to address these issues experimentally are discussed.

Stan-Lotter, Helga↗
NASA NTRS2000

Fluid Inclusions in Extraterrestrial Samples Fact or Fiction?

Over the years there have been numerous reports of liquid inclusions in meteorites. Roedder reviews the reported occurrences of liquid inclusions in meteorites and states that "silicate-melt inclusions are expectable and apparently ubiquitous, but the presence of actual liquid inclusions (i.e., with moving bubbles at room temperature) would seem almost impossible." The reason for this conclusion is that meteorites (presumably) form in space at high temperatures and very low pressures where liquid water (or carbon dioxide) is not stable. Perhaps the most infamous report of fluid inclusions in meteorites was that of Warner et al. In that study, the authors reported the presence of two-phase, liquid-vapor inclusions in a diogenite from Antarctica. This report of fluid inclusions generated considerable interest in the meteorite community, and caused many to question existing models for the origin of the diogenites. This interest was short-lived however, as later investigations of the same samples showed that the inclusions were most likely artifacts. Rudnick et al. showed that many of the inclusions in meteorites prepared at the Johnson Space Center contained a fluid that fluoresced strongly under the laser beam on the Raman microprobe. They interpreted this to indicate that the inclusions contained Almag oil used in the preparation of thin sections. Presumably, the Almag oil entered empty vesicles along fractures that were opened intermittently during cutting. Here, the occurrence of unambiguous fluid inclusions that could not have been introduced during sample preparation are described in samples from two different extraterrestrial environments. One environment is represented by the SNC (martian) meteorites ALH 84001 and Nakhla. The second environment is represented by the Monahans 1998 meteorite that fell recently in the USA.

Bodnar, R. J.↗
NASA NTRS2001

Low Stretch PMMA Burning in Microgravity: Status of the Ground-Based Program and New ISS Glovebox Experiment SALSA

The objective of this ground-based program is to study low stretch diffusion flames burning PMMA as the solid fuel to determine the relationship between buoyant low stretch burning in normal gravity and forced flow low stretch burning in microgravity. The low stretch is generated in normal gravity by using the buoyant convection induced by burning the bottom of a large radius of curvature sample. Low stretch is also generated using the Combustion Tunnel drop tower rig (2.2 and 5.2 second facilities), which provides a forced convective low velocity flow past smaller radius of curvature samples. Lastly, an ISS glovebox investigation is being developed to study low stretch burning of PMMA spheres to obtain long duration testing needed to accurately assess the flammability and burning characteristics of the material in microgravity. A comparison of microgravity experiment results with normal gravity test results allows us to establish a direct link between a material's burning characteristics in normal gravity (easily measured) with its burning characteristics in extraterrestrial environments, including microgravity forced convective environments. Theoretical predictions and recent experimental results indicate that it should be possible to understand a material's burning characteristics in the low stretch environment of spacecraft (non-buoyant air movement induced by fans and crew disturbances) by understanding its burning characteristics in an equivalent Earth-based low stretch environment (induced by normal gravity buoyancy). Similarly, Earth-based stretch environments can be made equivalent to those in Lunar- and Martian-surface stretch environments (which would induce partial-gravity buoyancy).

Olson, S. L.↗
NASA NTRS2001

An Earth-Based Equivalent Low Stretch Apparatus to Assess Material Flammability for Microgravity & Extraterrestrial Fire-Safety Applications

One of the performance goals for NASA's enterprise of Human Exploration and Development of Space (HEDS) is to develop methods, data bases, and validating tests for material flammability characterization, hazard reduction, and fire detection/suppression strategies for spacecraft and extraterrestrial habitats. This work addresses these needs by applying the fundamental knowledge gained from low stretch experiments to the development of a normal gravity low stretch material flammability test method. The concept of the apparatus being developed uses the low stretch geometry to simulate the conditions of the extraterrestrial environment through proper scaling of the sample dimensions to reduce the buoyant stretch in normal gravity. The apparatus uses controlled forced-air flow to augment the low stretch to levels which simulate Lunar or Martian gravity levels. In addition, the effect of imposed radiant heat flux on material flammability can be studied with the cone heater. After breadboard testing, the apparatus will be integrated into NASA's White Sands Test Facility's Atmosphere-Controlled Cone Calorimeter for evaluation as a new materials screening test method.

Olson, S. L.↗
NASA NTRS2003

CO2 Acquisition Membrane (CAM)

The objective of CAM is to develop, test, and analyze thin film membrane materials for separation and purification of carbon dioxide (CO2) from mixtures of gases, such as those found in the Martian atmosphere. The membranes are targeted toward In Situ Resource Utilization (ISRU) applications that will operate in extraterrestrial environments and support future unmanned and human space missions. A primary application is the Sabatier Electrolysis process that uses Mars atmosphere CO2 as raw material for producing water, oxygen, and methane for rocket fuel and habitat support. Other applications include use as an inlet filter to collect and concentrate Mars atmospheric argon and nitrogen gases for habitat pressurization, and to remove CO2 from breathing gases in Closed Environment Life Support Systems (CELSS). CAM membrane materials include crystalline faujasite (FAU) zeolite and rubbery polymers such as silicone rubber (PDMS) that have been shown in the literature and via molecular simulation to favor adsorption and permeation of CO2 over nitrogen and argon. Pure gas permeation tests using commercial PDMS membranes have shown that both CO2 permeance and the separation factor relative to other gases increase as the temperature decreases, and low (Delta)P(Sub CO2) favors higher separation factors. The ideal CO2/N2 separation factor increases from 7.5 to 17.5 as temperature decreases from 22 C to -30 C. For gas mixtures containing CO2, N2, and Ar, plasticization decreased the separation factors from 4.5 to 6 over the same temperature range. We currently synthesize and test our own Na(+) FAU zeolite membranes using standard formulations and secondary growth methods on porous alumina. Preliminary tests with a Na(+) FAU membrane at 22 C show a He/SF6 ideal separation factor of 62, exceeding the Knudsen diffusion selectivity by an order of magnitude. This shows that the membrane is relatively free from large defects and associated non-selective (viscous flow) transport mechanisms. The Membrane Test Facility (MTF) has been developed to measure membrane permeance over a wide range of temperature and pressure. The facility uses two volume compartments separated by the membrane that are instrumented to measure temperature, delta pressure across the membrane, and gas composition. A thermal shroud supports and encloses the membrane, and provides temperature control. Methods were developed to determine membrane permeance using the first order decay of the pressure difference between the sealed compartments, using the total pressure for pure gases, and partial pressure of each species in gas mixtures. The technique provides an end-to-end measurement of gas permeance that includes concentration polarization effects. Experiments have shown that in addition to membrane permeance properties, the geometry and design of associated structures play an important role in how membrane systems will function on Mars.

Mason, Larry W.↗
NASA NTRS2000

Structural Characterization of Crystalline Ice Nanoclusters

Water ice nanoclusters are useful analogs for studying a variety of processes that occur within icy grains in the extraterrestrial environment. The surface of ice nanoclusters prepared in the laboratory is similar to the surface of interstellar ice grains. In cold molecular clouds, the silicate cores of interstellar grains are typically approx. 100 nm in diameter and have a coating of impure amorphous water ice. Depositional, thermal and radiolytic processes leave the surface and subsurface molecules in a disordered state. In this state, structural defects become mobile and reactions of trapped gases and small molecules can occur. The large surface area of nanocluster deposits relative to their bulk allows for routine observation of such surface-mediated processes. Furthermore, the disordered surface and subsurface layers in nanocluster deposits mimic the structure of amorphous ice rinds found on interstellar dust grains. Transmission Electron Microscopy (TEM has been used tn characterize the crystallinity, growth mechanism, and size distribution of nanoclusters formed from a mixture of water vapor with an inert carrier gas that has been rapidly cooled to 77K. E M imaging reveals a Gaussian size distribution around a modal diameter that increases from approx. 15 to 30 nm as the percentage of water vapor within the mixture increases from 0.5 to 2.007, respectively . TEM bright and dark field imaging also reveals the crystalline nature of the clusters. h4any of the clusters show a mosaic structure in which crystalline domains originate at the center Other images show mirror planes that are separated by approx. 10 nm. Electron diffraction patterns of these clusters show that the clusters are composed of cubic ice with only a small hexagonal component. Further, the crystalline domain size is approximately the same as the modal diameter suggesting that the clusters are single crystals.

Blake, David↗
NASA NTRS1999

Gas chromatography in space

Gas chromatography has proven to be a very useful analytical technique for in situ analysis of extraterrestrial environments as demonstrated by its successful operation on spacecraft missions to Mars and Venus. The technique is also one of the six scientific instruments aboard the Huygens probe to explore Titan's atmosphere and surface. A review of gas chromatography in previous space missions and some recent developments in the current environment of fiscal constraints and payload size limitations are presented.

Review, Tutorial↗
NASA NTRS2004

Medusa Sea Floor Monitoring System

The objective of the research described in this poster presentation is to develop technologies to enable fundamental research into understanding the potential for and limits to chemolithoautotrophic life. The Medusa Isosampler (isobaric sampler), for sampling fluids eminating from deep sea hydrothermal vents and cold seep sites analogous to extraterrestrial environments, is described by the presentation. The following instruments are integrated with the isosampler, and also described: in situ flow-through chemical sensor, intrinsic fluorescent-based microbial detector, isotope ratio spectral detector.

Flynn, Michael↗
NASA NTRS2006

Heat Transfer of Thermocapillary Convection in a Two-Layered Fluid System Under the Influence of Magnetic Field

Heat transfer of a two-layer fluid system has been of great importance in a variety of industrial applications. For example, the phenomena of immiscible fluids can be found in materials processing and heat exchangers. Typically in solidification from a melt, the convective motion is the dominant factor that affects the uniformity of material properties. In the layered flow, thermocapillary forces can come into an important play, which was first emphasized by a previous investigator in 1958. Under extraterrestrial environments without gravity, thermocapillary effects can be a more dominant factor, which alters material properties in processing. Control and optimization of heat transfer in an immiscible fluid system need complete understanding of the flow phenomena that can be induced by surface tension at a fluid interface. The present work is focused on understanding of the magnetic field effects on thermocapillary convection, in order to optimize material processing. That is, it involves the study of the complicated phenomena to alter the flow motion in crystal growth. In this effort, the Marangoni convection in a cavity with differentially heated sidewalls is investigated with and without the influence of a magnetic field. As a first step, numerical analyses are performed, by thoroughly investigating influences of all pertinent physical parameters. Experiments are then conducted, with preliminary results, for comparison with the numerical analyses.

Ramachandran, N.↗
NASA NTRS2006

Uncooled long-wave infrared hyperspectral imaging

A long-wave infrared hyperspectral sensor device employs a combination of an interferometer with an uncooled microbolometer array camera to produce hyperspectral images without the use of bulky, power-hungry motorized components, making it suitable for UAV vehicles, small mobile platforms, or in extraterrestrial environments. The sensor device can provide signal-to-noise ratios near 200 for ambient temperature scenes with 33 wavenumber resolution at a frame rate of 50 Hz, with higher results indicated by ongoing component improvements.

Lucey, Paul G.↗
NASA NTRS2010

Mapping and Quantification of Vascular Branching in Plants, Animals and Humans by VESGEN Software

Humans face daunting challenges in the successful exploration and colonization of space, including adverse alterations in gravity and radiation. The Earth-determined biology of humans, animals and plants is significantly modified in such extraterrestrial environments. One physiological requirement shared by humans with larger plants and animals is a complex, highly branching vascular system that is dynamically responsive to cellular metabolism, immunological protection and specialized cellular/tissue function. The VESsel GENeration (VESGEN) Analysis has been developed as a mature beta version, pre-release research software for mapping and quantification of the fractal-based complexity of vascular branching. Alterations in vascular branching pattern can provide informative read-outs of altered vascular regulation. Originally developed for biomedical applications in angiogenesis, VESGEN 2D has provided novel insights into the cytokine, transgenic and therapeutic regulation of angiogenesis, lymphangiogenesis and other microvascular remodeling phenomena. Vascular trees, networks and tree-network composites are mapped and quantified. Applications include disease progression from clinical ophthalmic images of the human retina; experimental regulation of vascular remodeling in the mouse retina; avian and mouse coronary vasculature, and other experimental models in vivo. We envision that altered branching in the leaves of plants studied on ISS such as Arabidopsis thaliana cans also be analyzed.

Parsons-Wingerter, Patricia A.↗
NASA NTRS2011

Analysis of Mars Analogue Soil Samples Using Solid-Phase Microextraction, Organic Solvent Extraction and Gas Chromatography/Mass Spectrometry

Polycyclic aromatic hydrocarbons (PAHs) are robust and abundant molecules in extraterrestrial environments. They are found ubiquitously in the interstellar medium and have been identified in extracts of meteorites collected on Earth. PAHs are important target molecules for planetary exploration missions that investigate the organic inventory of planets, moons and small bodies. This study is part of an interdisciplinary preparation phase to search for organic molecules and life on Mars. We have investigated PAH compounds in desert soils to determine their composition, distribution and stability. Soil samples (Mars analogue soils) were collected at desert areas of Utah in the vicinity of the Mars Desert Research Station (MDRS), in the Arequipa region in Peru and from the Jutland region of Denmark. The aim of this study was to optimize the solid-phase microextraction (SPME) method for fast screening and determination of PAHs in soil samples. This method minimizes sample handling and preserves the chemical integrity of the sample. Complementary liquid extraction was used to obtain information on five- and six-ring PAH compounds. The measured concentrations of PAHs are, in general, very low, ranging from 1 to 60 ng g(sup -1). The texture of soils is mostly sandy loam with few samples being 100% silt. Collected soils are moderately basic with pH values of 8-9 except for the Salten Skov soil, which is slightly acidic. Although the diverse and variable microbial populations of the samples at the sample sites might have affected the levels and variety of PAHs detected, SPME appears to be a rapid, viable field sampling technique with implications for use on planetary missions.

Orzechowska, G. E.↗
NASA NTRS2012

In-Situ Measurements of the Radiation Stability of Amino Acids at 15-140 K

We present new kinetics data on the radiolytic destruction of amino acids measured in situ with infrared spectroscopy. Samples were irradiated at 15, 100, and 140 K with D.8-MeV protons, and amino-acid decay was followed at each temperature with and without H2O present. Observed radiation products included CO2 and amines, consistent with amino-acid decarboxylation. The half-lives of glycine, alanine, and phenylalanine were estimated for various extraterrestrial environments. Infrared spectral changes demonstrated the conversion from the non-zwitterion structure NH2-CH2(R)-COOH at 15 K to the zwitterion structure +NH3-CH2(R)-COO- at 140 K for each amino acid studied.

Gerakines, Perry A.↗
NASA NTRS2012

Walk Through Solar System Times: An Exhibit with an Astrobiology Emphasis

In this astrobiology outreach project, we attempt to present the research of the Goddard Center for Astrobiology (GCA) in the context of the history of the Solar System. GCA research emphasizes the origin and formation of complex pre-biotic organic materials in extraterrestrial environments and explores whether the delivery of these primordial materials and water to the early Earth enabled the emergence and evolution of life. The content expounds on areas that are usually not touched upon in a timeline of the Earth's formation. The exhibit addresses the questions: How did our solar system form? How is the formation of our solar systems similar or different from others? How did the organic molecules we observe in space get to the Earth? What conditions are most suitable for life? We will address the issues and challenges of designing the exhibit and of explaining advanced astrobiology research topics to the public.

Cheung, C. Y.↗