21,710 research outputs found

    Vacuum ultraviolet photoabsorption spectra of nitrile ices for their identification on Pluto

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    Icy bodies, such as Pluto, are known to harbor simple and complex molecules. The recent New Horizons flyby of Pluto has revealed a complex surface composed of bright and dark ice surfaces, indicating a rich chemistry based on nitrogen (N2), methane (CH4), and carbon monoxide (CO). Nitrile (CN) containing molecules such as acetonitrile (CH3CN), propionitrile (CH3CH2CN), butyronitrile (CH3CH2CH2CN), and isobutyronitrile ((CH3)2CHCN) are some of the nitrile molecules that are known to be synthesized by radiative processing of such simple ices. Through the provision of a spectral atlas for such compounds we propose that such nitriles may be identified from the ALICE payload on board New Horizons</i

    Inscribed Matter Communication: Part I

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    We provide a fundamental treatment of the molecular communication channel wherein "inscribed matter" is transmitted across a spatial gap to provide reliable signaling between a sender and receiver. Inscribed matter is defined as an ensemble of "tokens" (molecules, objects, and so on) and is inspired, at least partially, by biological systems where groups of individually constructed discrete particles ranging from molecules through membrane-bound structures containing molecules to viruses and organisms are released by a source and travel to a target -- for example, morphogens or semiochemicals diffuse from one cell, tissue or organism diffuse to another. For identical tokens that are neither lost nor modified, we consider messages encoded using three candidate communication schemes: a) token timing (timed release), b) token payload (composition), and c) token timing plus payload. We provide capacity bounds for each scheme and discuss their relative utility. We find that under not unreasonable assumptions, megabit per second rates could be supported at femtoWatt transmitter powers. Since quantities such as token concentration or bin-counting are derivatives of token arrival timing, individual token timing undergirds all molecular communication techniques. Thus, our modeling and results about the physics of efficient token-based information transfer can inform investigations of diverse theoretical and practical problems in engineering and biology. This work, Part I, focuses on the information theoretic bounds on capacity. Part II develops some of the mathematical and information-theoretic ideas that support the bounds presented here.Comment: 20 pages, 6 figures, 1 Table in revision at IEEE Journal on Molecular, Biological and Multiscale Communicatio

    Spacecraft external molecular contamination analysis

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    Control of contamination on and around spacecraft is required to avoid adverse effects on the performance of instruments and spacecraft systems. Recent work in this area is reviewed and discussed. Specific issues and limitations to be considered as part of the effort to predict contamination effects using modeling techniques are addressed. Significant results of Space Shuttle missions in the field of molecule/surface interactions as well as their implications for space station design and operation are reviewed

    Shuttle on-orbit contamination and environmental effects

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    Ensuring the compatibility of the space shuttle system with payloads and payload measurements is discussed. An extensive set of quantitative requirements and goals was developed and implemented by the space shuttle program management. The performance of the Shuttle system as measured by these requirements and goals was assessed partly through the use of the induced environment contamination monitor on Shuttle flights 2, 3, and 4. Contamination levels are low and generally within the requirements and goals established. Additional data from near-term payloads and already planned contamination measurements will complete the environment definition and allow for the development of contamination avoidance procedures as necessary for any payload

    ATLAS 1: Encountering Planet Earth

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    Several NASA science programs examine the dynamic balance of sunlight, atmosphere, water, land, and life that governs Earth's environment. Among these is a series of Space Shuttle-Spacelab missions, named the Atmospheric Laboratory for Applications and Science (ATLAS). During the ATLAS missions, international teams of scientists representing many disciplines combine their expertise to seek answers to complex questions about the atmospheric and solar conditions that sustain life on Earth. The ATLAS program specifically investigates how Earth's middle atmosphere and upper atmospheres and climate are affected by both the Sun and by products of industrial and agricultural activities on Earth

    Life-Detection Technologies for the Next Two Decades

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    Since its inception six decades ago, astrobiology has diversified immensely to encompass several scientific questions including the origin and evolution of Terran life, the organic chemical composition of extraterrestrial objects, and the concept of habitability, among others. The detection of life beyond Earth forms the main goal of astrobiology, and a significant one for space exploration in general. This goal has galvanized and connected with other critical areas of investigation such as the analysis of meteorites and early Earth geological and biological systems, materials gathered by sample-return space missions, laboratory and computer simulations of extraterrestrial and early Earth environmental chemistry, astronomical remote sensing, and in-situ space exploration missions. Lately, scattered efforts are being undertaken towards the R&D of the novel and as-yet-space-unproven life-detection technologies capable of obtaining unambiguous evidence of extraterrestrial life, even if it is significantly different from Terran life. As the suite of space-proven payloads improves in breadth and sensitivity, this is an apt time to examine the progress and future of life-detection technologies.Comment: 6 pages, the white paper was submitted to and cited by the National Academy of Sciences in support of the Astrobiology Science Strategy for the Search for Life in the Univers

    Payload/orbiter contamination control assessment support

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    The development and use is described of a basic contamination mathematical model of the shuttle orbiter which incorporates specific shuttle orbiter configurations and contamination sources. These configurations and sources were evaluated with respect to known shuttle orbiter operational surface characteristics and specific lines-of-sight which encompass the majority of viewing requirements for shuttle payloads. The results of these evaluations are presented as summary tables for each major source. In addition, contamination minimization studies were conducted and recommendations are made, where applicable, to support the shuttle orbiter design and operational planning for those sources which were identified to present a significant contamination threat
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