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  • 1
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    Europa's surface color suggests an ocean rich with sodium chloride (2015)
    Wiley
    Details
    Publication Date: 2015-04-23
    Description: The composition of Europa's surface may be representative of the subsurface ocean, however, considerable debate persists regarding the endogenous or exogenous nature of a hydrated sulfate feature on Europa. Direct evidence of oceanic salts on Europa's surface has been largely inconclusive. We show that the observed color within geologically young features on Europa's surface can be explained by sodium chloride delivered from the ocean below. We find that sodium chloride, when exposed to Europa surface conditions, accumulates electrons in F- and M-centers, yielding a yellow-brown discoloration comparable to Europa's surface. Irradiation of sodium chloride from Europa's ocean thus provides a simple and elegant solution to the color of the non-ice material observed on Europa. This evidence for endogenous salts suggests that Europa's ocean is interacting with a silicate seafloor, a critical consideration for assessing habitability.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Laboratory spectroscopic analyses of electron irradiated alkanes and alkenes in solar system ices (2012)
    Wiley
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    Publication Date: 2012-03-16
    Description: We report results from laboratory experiments of 10 keV electron irradiation of thin ice films of water and short-chain hydrocarbons at ∼10−8 Torr and temperatures ranging from 70–100 K. Hydrocarbon mixtures include water with C3H8, C3H6, C4H10 (butane and isobutane), and C4H8, (1-butene and cis/trans-2-butene). The double bonds of the alkenes in our initial mixtures were rapidly destroyed or converted to single carbon bonds, covalent bonds with hydrogen, bonds with −OH (hydroxyl), bonds with oxygen (C-O), or double bonds with oxygen (carbonyl). Spectra resulting from irradiation of alkane and alkene ices are largely indistinguishable; the initial differences in film composition are destroyed and the resulting mixture includes long-chain, branched aliphatics, aldehydes, ketones, esters, and alcohols. Methane was observed as a product during radiolysis but CO was largely absent. We find that while some of the carbon is oxidized and lost to CO2 formation, some carbon is sequestered into highly refractory, long-chain aliphatic compounds that remain as a thin residue even after the ice film has been raised to standard temperature and pressure. We conclude that the high availability of hydrogen in our experiments leads to the formation of the formyl radical which then serves as the precursor for formaldehyde and polymerization of longer hydrocarbon chains.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Joule heating of the south polar terrain on Enceladus (2011)
    Wiley
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    Publication Date: 2011-04-27
    Description: We report that Joule heating in Enceladus, resulting from the interaction of Enceladus with Saturn's magnetic field, may account for 150 kW to 52 MW of power through Enceladus. Electric currents passing through subsurface channels of low salinity and just a few kilometers in depth could supply a source of power to the south polar terrain, providing a small but previously unaccounted for contribution to the observed heat flux and plume activity. Studies of the electrical heating of Jupiter's moon Europa have concluded that electricity is a negligible heating source since no connection between the conductive subsurface and Alfvén currents has been observed. Here we show that, contrary to results for the Jupiter system, electrical heating may be a source of internal energy for Enceladus, contributing to localized heating, production of water vapor, and the persistence of the “tiger stripes.” This contribution is of order 0.001–0.25% of the total observed heat flux, and thus, Joule heating cannot explain the total south polar terrain heat anomaly. The exclusion of salt ions during refreezing serves to enhance volumetric Joule heating and could extend the lifetime of liquid water fractures in the south polar terrain.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Differential Incorporation of Bacteria, Organic Matter, and Inorganic Ions into Lake Ice during Ice Formation (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract The segregation of bacteria, inorganic solutes, and total organic carbon between liquid water and ice during winter ice formation on lakes can significantly influence the concentration and survival of microorganisms in icy systems, and their roles in biogeochemical processes. Our study quantifies the distributions of bacteria and solutes between liquid and solid water phases during progressive freezing. We simulated lake ice formation in mesocosm experiments using water from perennially (Antarctica) and seasonally (Alaska and Montana, USA) ice covered lakes. We then computed concentration factors and effective segregation coefficients, which are parameters describing the incorporation of bacteria and solutes into ice. Experimental results revealed that, contrary to major ions, bacteria were readily incorporated into ice and did not concentrate in the liquid phase. The organic matter incorporated into the ice was labile, amino acid‐like material, differing from the humic‐like compounds that remained in the liquid phase. Results from a control mesocosm experiment (dead bacterial cells) indicated that viability of bacterial cells did not influence the incorporation of free bacterial cells into ice, but did have a role in the formation and incorporation of bacterial aggregates. Together, these findings demonstrate that bacteria, unlike other solutes, were preferentially incorporated into lake‐ice during our freezing experiments, a process controlled mainly by the initial solute concentration of the liquid water source, regardless of cell viability.
    Print ISSN: 2169-8953
    Electronic ISSN: 2169-8961
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Planetary science. Life without photosynthesis (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-06-16
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chyba, C F -- Hand, K P -- New York, N.Y. -- Science. 2001 Jun 15;292(5524):2026-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for the Study of Life in the Universe, SETI Institute, Mountain View, CA 94404, USA. chyba@seti.org〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11408649" target="_blank"〉PubMed〈/a〉
    Keywords: Biomass ; Carbon ; *Exobiology ; *Extraterrestrial Environment ; Hydrogen ; Hydrogen Peroxide ; Ice ; *Jupiter ; Meteoroids ; Oxidation-Reduction ; *Oxygen/chemistry ; Photosynthesis ; Potassium ; Water
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    Geophysical controls of chemical disequilibria in Europa (2016)
    Wiley
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    Publication Date: 2016-05-18
    Description: The ocean in Jupiter's moon Europa may have redox balance similar to Earth's. On Earth, low-temperature hydration of crustal olivine produces substantial hydrogen, comparable to any potential flux from volcanic activity. Here, we compare hydrogen and oxygen production rates of the Earth system with fluxes to Europa's ocean. Even without volcanic hydrothermal activity, water-rock alteration in Europa causes hydrogen fluxes ten times smaller than Earth's. Europa's ocean may have become reducing for a brief epoch, for example after a thermal-orbital resonance ∼2 Gyr after accretion. Estimated oxidant flux to Europa's ocean is comparable to estimated hydrogen fluxes. Europa's ice delivers oxidants to its ocean at the upper end of these estimates if its ice is geologically active, as evidence of geologic activity and subduction implies.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Astrobiology: Frontier or fiction (2012)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2012-08-10
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lazcano, Antonio -- Hand, Kevin P -- England -- Nature. 2012 Aug 9;488(7410):160-1. doi: 10.1038/488160a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22874956" target="_blank"〉PubMed〈/a〉
    Keywords: Biological Evolution ; *Exobiology/trends ; Extraterrestrial Environment/*chemistry ; Mars ; Origin of Life ; Reproducibility of Results ; Solar System/*chemistry ; *Space Flight/trends ; United States ; United States National Aeronautics and Space Administration
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 8
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    Metabolic mapping of functional activity in human subjects with the [18F]fluorodeoxyglucose technique (1981)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1981-05-08
    Description: The 2-[18F]fluoro-2-deoxy-D-glucose technique was used to measure regional cerebral glucose utilization by human subjects during functional activation. Normal male volunteers subjected to one or more sensory stimuli (tactile, visual, or auditory) exhibited focal increases in glucose metabolism in response to the stimulus. Unilateral visual hemifield stimulation caused the contralateral striate cortex to become more metabolically active than the striate cortex ipsilateral to the stimulated hemifield. Similarly, stroking the fingers and hand of one arm with brush produced an increase in metabolism in the contralateral postcentral gyrus, compared with the homologous ipsilateral region. The auditory stimulus, which consisted of a monaurally presented factual story caused an increase in glucose metabolism in the auditory cortex in the hemisphere contralateral to the stimulated ear. These results demonstrate that the technique is capable of providing functional maps in vivo related to both body region and submodality of sensory information in the human brain.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Greenberg, J H -- Reivich, M -- Alavi, A -- Hand, P -- Rosenquist, A -- Rintelmann, W -- Stein, A -- Tusa, R -- Dann, R -- Christman, D -- Fowler, J -- MacGregor, B -- Wolf, A -- NS 10939-08/NS/NINDS NIH HHS/ -- NS 14867-02/NS/NINDS NIH HHS/ -- NS 15380-04/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1981 May 8;212(4495):678-80.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6971492" target="_blank"〉PubMed〈/a〉
    Keywords: Adult ; Auditory Perception/*physiology ; Brain/*metabolism ; *Deoxy Sugars ; *Deoxyglucose/analogs & derivatives/metabolism ; Fluorodeoxyglucose F18 ; Functional Laterality ; Humans ; Male ; Sensation/*physiology ; Tomography, Emission-Computed/*methods ; Visual Perception/*physiology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    Spectral Behavior of Irradiated Sodium Chloride Crystals Under Europa-Like Conditions (2017)
    Wiley
    Details
    Publication Date: 2017-11-23
    Description: F- and M-color center formation (decay) was observed during (after) irradiation of sodium chloride crystal grains with 10 keV electrons as a function of temperature, radiation dose rate, and radiation dose. The F-centers (peak center: 460 nm) were found to form and decay at a faster rate than the M-centers (peak center: 720 nm). These effects were influenced by temperature, and possibly by irradiation dose rate. Tracking the band depth ratio of the color center features during irradiation could enable age determination of geologically very-young features on the surface of Europa and other icy ocean worlds.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
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    Electric Power Generation from Earth’s Rotation through its Own Magnetic Field (2016)
    American Physical Society (APS)
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    Publication Date: 2016-10-12
    Description: Author(s): Christopher F. Chyba and Kevin P. Hand There is a simple proof that it is impossible to produce electricity using Earth’s rotation through the nonrotating component of its own magnetic field. However, the authors have identified a loophole in that proof, and it appears that power generation could be possible in a laboratory system. Experimental verification of this result could carry implications for a clean-energy future. [Phys. Rev. Applied 6, 014017] Published Fri Jul 29, 2016
    Electronic ISSN: 2331-7019
    Topics: Physics
    Published by American Physical Society (APS)
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