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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Evidence from carbon isotope measurements for diverse origins of sedimentary hydrocarbons

The organic matter found in sedimentary rocks must derive from many sources; not only from ancient primary producers but also from consumers and secondary producers. In all of these organisms, isotope effects can affect the abundance and distribution of 13C in metabolites. Here, by using an improved form of a previously described technique in which the effluent of a gas chromatograph is continuously analysed isotopically, we report evidence of the diverse origins of sedimentary organic matter. The record of 13C abundances in sedimentary carbonate and total organic carbon can be interpreted in terms of variations in the global carbon cycle. Our results demonstrate, however, that isotope variations within sedimentary organic mixtures substantially exceed those observed between samples of total organic carbon. Resolution of isotope variations at the molecular level offers a new and convenient means of refining views both of localized palaeoenvironments and of control mechanisms within the global carbon cycle.

Non-NASA Center↗
NASA NTRS1991

A model of onshore-offshore change in faunal diversity

Onshore-offshore patterns of faunal change occurred at many taxonomic scales during the Paleozoic Era, ranging from replacement of the Cambrian evolutionary fauna by the Paleozoic fauna to the environmental expansion of many orders and classes. A simple mathematical model is constructed to investigate such change. The environmental gradient across the marine shelf-slope is treated as a linear array of discrete habitats, each of which holds a set number of species, as observed in the fossil record. During any interval of time, some portion of the species in each habitat becomes extinct by background processes, with rates of extinction varying among both clades and habitats, as also observed in the record. After extinction, species are replaced from within the habitat and from immediately adjacent habitats, with proportions dependent on surviving species. This model leads to the prediction that extinction-resistant clades will always diversify at the expense of extinction-prone clades. But if extinction intensity is highest in nearshore habitats, extinction-resistant clades will expand preferentially in the onshore direction, build up diversity there, and then diversify outward toward the offshore. Thus, onshore-offshore patterns of diversification may be the expectation for faunal change quite independently of whether or not clades originate onshore. When the model is parameterized for Paleozoic trilobites and brachiopods, numerical solutions exhibit both a pattern of faunal change and a time span for diversification similar to that seen in the fossil record. They also generate structure similar to that seen in global diversification, including logistic patterns of growth, declining origination but constant extinction within clades through time, and declining overall extinction across clades through time.

NASA Discipline Number 52-40↗
NASA NTRS2005

Spectral Diversity at Gusev Crater from Coordinated Mini-TES and Pancam Observations

During the last year the Spirit rover has explored Gusev crater with the Athena payload. Two remote sensing instruments collected spectral information at visible (Pancam) and at thermal infrared Mini-TES) wavelengths. Observations for these instruments were coordinated and targeted to determine the mineralogical diversity and identify specific lithologies / end members for detailed investigations with the rest of the payload. Initial results were reported last spring. A wide range of materials have been measured including outcrops, rocks, and soils. Both natural and brushed/ratted rocks and natural and disturbed soils have also been measured permitting investigations of coating and soil structure. As of Jan 9, 2005, over 400 coordinated observations have been made.

Blaney, D. L.↗
NASA NTRS2005

Diverse Applications of Occultation Data in Ozone Assimilation

Ozone profiles from solar occultation instruments provide invaluable information that can be used to evaluate the quality of assimilated ozone fields, from case studies to long-term phenomena. Occultation data can also be applied to include physical constraints while developing components of an assimilation system. Conversely, assimilation of occultation data can help in their validation, and it provides a framework for evaluation of the impact of occultation data on constraining global ozone fields within models. We illustrate these diverse applications by a series of examples using the ozone assimilation system at NASA/Goddard. In a case study, low ozone in the lower stratosphere due to transport of air from the Tropics to northern high latitudes that was captured by assimilation of Aura Microwave Limb Sounder (MLS) and Solar Backscatter Ultraviolet (SBUV) data, was found to agree with SAGE III data. For long-term monitoring, the quality of a multi-year SBUV-only assimilation was evaluated using monthly-mean time series of POAM, HALOE, and SAGE I1 data. We found realism in the representation of the annual cycle in ozone and in some aspects of interannual variability. Assimilation of POAM data was shown to improve the representation of lower stratospheric ozone, especially over Antarctica. More recently, we assimilated ILAS II ozone data in order to help in their validation. Solar occultation data are used to estimate parameters in a new model for forecast error variances that is being developed. These examples demonstrate the importance of occultation data for ozone assimilation, and potential of assimilation to increase the impact and the value of occultation data.

Markowitz, A.↗
NASA NTRS2004

Microbial structural diversity estimated by dilution-extinction of phenotypic traits and T-RFLP analysis along a land-use intensification gradient

The present work tested whether the relationship between functional traits and inoculum density reflected structural diversity in bacterial communities from a land-use intensification gradient applying a mathematical model. Terminal restriction fragment length polymorphism (T-RFLP) analysis was also performed to provide an independent assessment of species richness. Successive 10-fold dilutions of a soil suspension were inoculated onto Biolog GN(R) microplates. Soil bacterial density was determined by total cell and plate counts. The relationship between phenotypic traits and inoculum density fit the model, allowing the estimation of maximal phenotypic potential (Rmax) and inoculum density (KI) at which Rmax will be half-reduced. Though Rmax decreased with time elapsed since clearing of native vegetation, KI remained high in two of the disturbed sites. The genetic pool of bacterial community did not experience a significant reduction, but the active fraction responding in the Biolog assay was adversely affected, suggesting a reduction in the functional potential. c2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.

NASA Center KSC↗
NASA NTRS2001

Developing planetary protection technology- microbial diversity of the Mars Orbiter Odyssey and the spacecraft assembly and encapsulation facility II

A study in which several surface samples, retrieved from both the Mars Odyssey Spacecraft and the Kennedy Space Center (KSC) Spacecraft Assembly and Encapsulation Facility II (SAEF-II), were prcesed and evaluated by both molecular and traditional culture-based methods for the microbial diversity.

Odyssey spacecraft microbial assembly facility↗
NASA NTRS2003

Optical ground station site diversity for Deep Space Optical Communications the Mars Telecom Orbiter optical link

Future NASA deep space missions will fly advanced high resolution imaging instruments that will require high bandwidth links to return the huge data volumes generated by these instruments. Optical communications is a key technology for returning these large data volumes from deep space probes. Yet to cost effectively realize the high bandwidth potential of the optical link will require deployment of ground receivers in diverse locations to provide high link availability. A recent analysis of GOES weather satellite data showed that a network of ground stations located in Hawaii and the Southwest continental US can provide an average of 90% availability for the deep space optical link. JPL and AFRL are exploring the use of large telescopes in Hawaii, California, and Albuquerque to support the Mars Telesat laser communications demonstration. Designed to demonstrate multi-Mbps communications from Mars, the mission will investigate key operational strategies of future deep space optical communications network.

laser communications↗
NASA NTRS2008

A Simplified View of the Geochemical Diversity Surrounding Home Plate

The Home Plate feature (Fig. 1) within the Inner Basin of the Columbia Hills consists of layered rocks and has been interpreted as an accumulation of pyroclastic deposits [1]. Samples analyzed by the Alpha Particle X-ray Spectrometer within ~25 meters of the eastern margin of Home Plate exhibit a strikingly diverse range of geochemical compositions, including the highest levels of Mg, Si, K, Zn, and Ni measured at Gusev Crater. This wide range of chemical variability across the 40+ samples analyzed on and near Home Plate can be represented by contributions from only six primary components. This reconstruction is not reflected in the M ssbauer mineralogy suggesting that significant alteration of the contributing components has occurred.

Yen, A. S.↗
NASA NTRS2008

Diversity and Physiology of Siderophilic Cyanobacteria: Implication for the Bioenergetics

Prior to 2.4 Ga, global oceans were likely significantly enriched in soluble iron (Rouxel, Bekker, Edwards, 2005), a condition that is not conducive to the growth of most contemporary mesophilic cyanobacteria (CB). Recent studies of the mechanisms of iron-deficiency stress in CB suggest that contemporary mesophilic freshwater and marine B underwent long-term adaptation to a permanent decrease in soluble iron in the ocean environment (Boyer, et al., 1987; Braun, Hantke, and Koster, 1998). Of all extant environments, iron-depositing hot springs may constitute the most appropriate natural models for analysis of the transition of ancestral cyanobacteria (CB) or protocyanobacteria (PCB) (Olson, 2001) from anoxygenic photosynthesis to oxygenic one and biogeochemical processes in the late Archean and early Paleoproterozoic eras. In particular, Olson (2001) proposed the definition for PCB and postulated that the common ancestor of PCB and CB might well have used Fe(OH)+ as the principal electron donor for CO2 fixation (Widdel, et al., 1993; Ehrenreich and Widdel, 1994; Pierson and Olson, 1989; Olson, 2006). Olson (2001) proposed that the driving force for the evolution of RC2, in addition to RC1, was the necessity to use Fe(OH)+ effectively for CO2 fixation in the absence of reduced sulfur compounds. The global decrease of dissolved environmental reduced iron could have been the driving force for the transition from anoxygenic to oxygenic photosynthesis (Brown et al., 2007). Despite the insights into the ecology, evolutionary biology, paleogeobiochemistry, and astrobiology the examination of iron depositing hot springs (IDHS) could potentially provide, very few studies dedicated to the diversity and physiology of cyanobacteria inhabiting IDHS have been conducted. Here we describe the phylogeny, physiology and ultrastructure and biogeochemical activity of several recent CB isolates from two different greater Yellowstone area IDHS, e.g. LaDuke and Chocolate Pots. Phylogenetic analysis of 16S rRNA genes indicated that 6 of 12 new isolates examined could not be placed within established CB genera. Some of the isolates exhibited pronounced requirements for elevated iron concentrations, with maximum growth rates observed when 0.4-1 mM Fe(3+) was present in the media. However, the pronounced effect of iron limitation on the proliferation of siderophilic CB can be observed only after several passages through iron "free" media. TEM studies of several species of siderophilic CB revealed that the cultures JSC-3 and -11 are probably capable of some sort of pinocytosis of precipitated iron. This phenomenon may explain high tolerance of siderophilic CB to iron deficit. We also found that the stimulation of the growth of siderophilic CB by oxidized iron is accompanied by the decrease of O2 evolution by some species after addition Fe(2+) in iron "free" medium.

Brown, Igor↗
NASA NTRS2006

The Incredible Diversity of Fe-bearing Phases at Gusev Crater, Mars, According to the Mars Exploration Rover Moessbauer Spectrometer

The Mars Exploration Rover (MER) Spirit landed on the plains of Gusev Crater on 4 January 2004. One primary scientific objective for the mission is to characterize the mineralogical and elemental composition of surface materials, searching for evidence of water and clues for assessing past and current climates and their suitability for life [1]. The role of the Moessbauer (MB) spectrometer on Spirit is to provide quantitative information about the distribution of Fe among its oxidation and coordination states, identification of Fe-bearing phases, and relative distribution of Fe among those phases. The speciation and distribution of Fe in Martian rock and soil constrains the primary rock types, redox conditions under which primary minerals crystallized, the extent of alteration and weathering, the type of alteration and weathering products, and the processes and environmental conditions for alteration and weathering. In this abstract, we discuss the incredible diversity of Fe-bearing phases detected by Spirit s MB instrument during its first 540 sols of exploration at Gusev crater [2,3].

Morris, R. V.↗
NASA NTRS2007

Closed Loop, DM Diversity-based, Wavefront Correction Algorithm for High Contrast Imaging Systems

High contrast imaging from space relies on coronagraphs to limit diffraction and a wavefront control systems to compensate for imperfections in both the telescope optics and the coronagraph. The extreme contrast required (up to 10(exp -10) for terrestrial planets) puts severe requirements on the wavefront control system, as the achievable contrast is limited by the quality of the wavefront. This paper presents a general closed loop correction algorithm for high contrast imaging coronagraphs by minimizing the energy in a predefined region in the image where terrestrial planets could be found. The estimation part of the algorithm reconstructs the complex field in the image plane using phase diversity caused by the deformable mirror. This method has been shown to achieve faster and better correction than classical speckle nulling.

Give'on, Amir↗
NASA NTRS2008

Phase Matching of Diverse Modes in a WGM Resonator

Phase matching of diverse electromagnetic modes (specifically, coexisting optical and microwave modes) in a whispering-gallery-mode (WGM) resonator has been predicted theoretically and verified experimentally. Such phase matching is necessary for storage of microwave/terahertz and optical electromagnetic energy in the same resonator, as needed for exploitation of nonlinear optical phenomena. WGM resonators are used in research on nonlinear optical phenomena at low optical intensities and as a basis for design and fabrication of novel optical devices. Examples of nonlinear optical phenomena recently demonstrated in WGM resonators include low-threshold Raman lasing, optomechanical oscillations, frequency doubling, and hyperparametric oscillations. The present findings regarding phase matching were made in research on low-threshold, strongly nondegenerate parametric oscillations in lithium niobate WGM resonators. The principle of operation of such an oscillator is rooted in two previously observed phenomena: (1) stimulated Raman scattering by polaritons in lithium niobate and (2) phase matching of nonlinear optical processes via geometrical confinement of light. The oscillator is partly similar to terahertz oscillators based on lithium niobate crystals, the key difference being that a novel geometrical configuration of this oscillator supports oscillation in the regime. The high resonance quality factors (Q values) typical of WGM resonators make it possible to achieve oscillation at a threshold signal level much lower than that in a non-WGM-resonator lithium niobate crystal.

Savchenkov, Anatoliy↗
NASA NTRS2010

Microbial Diversity in Surface Iron-Rich Aqueous Environments: Implications for Seeking Signs of Life on Mars

The success of selecting future landing sites on Mars to discover extinct and/or extant extraterrestrial life is dependent on the correct approximation of available knowledge about terrestrial paleogeochemistry and life evolution to Martian (paleo) geology and geochemistry. It is well known that both Earth and Mars are Fe rich. This widespread occurrence suggests that Fe may have played a key role in early life forms, where it probably served as a key constituent in early prosthetic moieties in many proteins of ancient microbes on Earth and likely Mars. The second critical idea is the premise that Life on Mars could most likely have developed when Mars experienced tectonic activity [1] which dramatically decreased around 1 bin years after Martian creation. After that Martian life could have gone extinct or hibernated in the deep subsurface, which would be expensive to reach in contrast to the successful work of Martian surface rovers. Here we analyze the diversity of microbes in several terrestrial Fe rich surface environments in conjunction with the phylogeny and molecular timing of emergence of those microbes on Earth. Anticipated results should help evaluate future landing sites on Mars in searches for biosignatures.

Brown, I. I.↗
NASA NTRS2010

Synergy of VSWIR and LiDAR for Ecosystem Structure, Biomass, and Canopy Diversity

This slide presentation reviews the use of Visible ShortWave InfraRed (VSWIR) Imaging Spectrometer and LiDAR to study ecosystem structure, biomass and canopy diversity. It is shown that the biophysical data from LiDAR and biochemical information from hyperspectral remote sensing provides complementary data for: (1) describing spatial patterns of vegetation and biodiversity, (2) characterizing relationships between ecosystem form and function, and (3) detecting natural and human induced change that affects the biogeochemical cycles.

Cook, Bruce D.↗
NASA NTRS2003

Microbial Diversity Aboard Spacecraft: Evaluation of the International Space Station

An evaluation of the microbial flora from air, water, and surface samples provided a baseline of microbial diversity onboard the International Space Station (ISS) to gain insight into bacterial and fungal contamination during the initial stages of construction and habitation. Using 16S genetic sequencing and rep-PeR, 63 bacterial strains were isolated for identification and fingerprinted for microbial tracking. The use of these molecular tools allowed for the identification of bacteria not previously identified using automated biochemical analysis and provided a clear indication of the source of several ISS contaminants. Fungal and bacterial data acquired during monitoring do not suggest there is a current microbial hazard to the spacecraft, nor does any trend indicate a potential health risk. Previous spacecraft environmental analysis indicated that microbial contamination will increase with time and require continued surveillance.

Castro, Victoria A.↗
NASA NTRS2011

Vegetation Water Content Mapping in a Diverse Agricultural Landscape: National Airborne Field Experiment 2006

Mapping land cover and vegetation characteristics on a regional scale is critical to soil moisture retrieval using microwave remote sensing. In aircraft-based experiments such as the National Airborne Field Experiment 2006 (NAFE 06), it is challenging to provide accurate high resolution vegetation information, especially on a daily basis. A technique proposed in previous studies was adapted here to the heterogenous conditions encountered in NAFE 06, which included a hydrologically complex landscape consisting of both irrigated and dryland agriculture. Using field vegetation sampling and ground-based reflectance measurements, the knowledge base for relating the Normalized Difference Water Index (NDWI) and the vegetation water content was extended to a greater diversity of agricultural crops, which included dryland and irrigated wheat, alfalfa, and canola. Critical to the generation of vegetation water content maps, the land cover for this region was determined from satellite visible/infrared imagery and ground surveys with an accuracy of 95.5% and a kappa coefficient of 0.95. The vegetation water content was estimated with a root mean square error of 0.33 kg/sq m. The results of this investigation contribute to a more robust database of global vegetation water content observations and demonstrate that the approach can be applied with high accuracy. Keywords: Vegetation, field experimentation, thematic mapper, NDWI, agriculture.

Cosh, Michael H.↗
NASA NTRS2011

Methods of Antimicrobial Coating of Diverse Materials

Methods of coating diverse substrate materials with antimicrobial agents have been developed. Originally intended to reduce health risks to astronauts posed by pathogenic microorganisms that can grow on surfaces in spacecraft, these methods could also be used on Earth for example, to ensure sterility of surgical inserts and other medical equipment. The methods involve, generally, chemical preparation of substrate surfaces to enable attachment of antimicrobial molecules to the substrate surfaces via covalent bonds. Substrate materials that have been treated successfully include aluminum, glass, a corrosion-resistant nickel alloy, stainless steel, titanium, and poly(tetrafluoroethylene). Antimicrobial agents that have been successfully immobilized include antibiotics, enzymes, bacteriocins, bactericides, and fungicides. A variety of linkage chem istries were employed. Activity of antimicrobial coatings against gram-positive bacteria, gram-negative bacteria, and fungi was demonstrated. Results of investigations indicate that the most suitable combination of antimicrobial agent, substrate, and coating method depends upon the intended application.

Akse, James R.↗
NASA NTRS2011

Microbial Diversity Analysis of the Bacterial and Archaeal Population in Present Day Stromatolites

Stromatolites are layered sedimentary structures resulting from microbial mat communities that remove carbon dioxide from their environment and biomineralize it as calcium carbonate. Although prevalent in the fossil record, stromatolites are rare in the modem world and are only found in a few locations including Highbome Cay in the Bahamas. The stromatolites found at this shallow marine site are analogs to ancient microbial mat ecosystems abundant in the Precambrian period on ancient Earth. To understand how stromatolites form and develop, it is important to identify what microorganisms are present in these mats, and how these microbes contribute to geological structure. These results will provide insight into the molecular and geochemical processes of microbial communities that prevailed on ancient Earth. Since stromatolites are formed by lithifying microbial mats that are able to mineralize calcium carbonate, understanding the biological mechanisms involved may lead to the development of carbon sequestration technologies that will be applicable in human spaceflight, as well as improve our understanding of global climate and its sustainability. The objective of my project was to analyze the archaeal and bacterial dIversity in stromatolites from Highborn Cay in the Bahamas. The first step in studying the molecular processes that the microorganisms carry out is to ascertain the microbial complexity within the mats, which includes identifying and estimating the numbers of different microbes that comprise these mats.

Ortega, Maya C.↗