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Caltech Authors (160.010 recursos)

Repository of works by Caltech published authors.

Group = Keck Institute for Space Studies

Mostrando recursos 1 - 20 de 98

  1. Assessment of errors and biases in retrievals of X_(CO2), X_(CH4), X_(CO), and X_(N2O) from a 0.5 cm^(-1) resolution solar-viewing spectrometer

    Hedelius, Jacob K.; Viatte, Camille; Wunch, Debra; Roehl, Coleen M.; Toon, Geoffrey C.; Chen, Jia; Jones, Taylor; Wofsy, Steven C.; Franklin, Jonathan E.; Parker, Harrison; Dubey, Manvendra K.; Wennberg, Paul O.
    Bruker™ EM27/SUN instruments are commercial mobile solar-viewing near-IR spectrometers. They show promise for expanding the global density of atmospheric column measurements of greenhouse gases and are being marketed for such applications. They have been shown to measure the same variations of atmospheric gases within a day as the high-resolution spectrometers of the Total Carbon Column Observing Network (TCCON). However, there is little known about the long-term precision and uncertainty budgets of EM27/SUN measurements. In this study, which includes a comparison of 186 measurement days spanning 11 months, we note that atmospheric variations of X_(gas) within a single day are well...

  2. Methane: Fuel or Exhaust at the Emergence of Life?

    Russell, Michael J.; Nitschke, Wolfang
    As many of the methanogens first encountered at hydrothermal vents were thermophilic to hyperthermophilic and comprised one of the lower roots of the evolutionary tree, it has been assumed that methanogenesis was one of the earliest, if not the earliest, pathway to life. It being well known that hydrothermal springs associated with serpentinization also bore abiotic methane, it had been further assumed that emergent biochemistry merely adopted and quickened this supposed serpentinization reaction. Yet, recent hydrothermal experiments simulating serpentinization have failed to generate methane so far, thus casting doubt on this assumption. The idea that the inverse view is worthy...

  3. Satellites to the Seafloor: Autonomous Science to Forge a Breakthrough in Quantifying the Global Ocean Carbon Budget

    Thompson, Andrew; Kinsey, James C.; Coleman, Max; Castaño, Rebecca; Adkins, Jess F.; Lazar, Ayah
    Understanding the global carbon budget and its changes is crucial to current and future life on Earth. The marine component represents the largest reservoir of the global carbon cycle. In addition to physical processes that govern carbon fluxes at the air-sea interface and regulate the atmospheric carbon budget, complex internal sources and sinks, including inorganic, geologic, microbiological and biological processes also impact carbon distributions and storage. Therefore, it is essential to observe and understand the whole system. This is a daunting task, as many of the processes are distributed throughout the ocean, laterally and vertically over scales ranging from centimeters...

  4. Satellites to Seafloor: Toward Fully Autonomous Ocean Sampling

    Thompson, Andrew F.; Chao, Yi; Chien, Steve; Kinsey, James; Flexas, M. Mar; Erickson, Zachary K.; Farrara, John; Fratantoni, David; Branch, Andrew; Chu, Selina; Troesch, Martina; Claus, Brian; Kepper, James
    Future ocean observing systems will rely heavily on autonomous vehicles to achieve the persistent and heterogeneous measurements needed to understand the ocean’s impact on the climate system. The day-to-day maintenance of these arrays will become increasingly challenging if significant human resources, such as manual piloting, are required. For this reason, techniques need to be developed that permit autonomous determination of sampling directives based on science goals and responses to in situ, remote-sensing, and model-derived information. Techniques that can accommodate large arrays of assets and permit sustained observations of rapidly evolving ocean properties are especially needed for capturing interactions between physical...

  5. Production of Sulfur Allotropes in Electron Irradiated Jupiter Trojans Ice Analogs

    Mahjoub, Ahmed; Poston, Michael J.; Blacksberg, Jordana; Eiler, John M.; Brown, Michael E.; Ehlmann, Bethany L.; Hodyss, Robert; Hand, Kevin P.; Carlson, Robert; Choukroun, Mathieu
    In this paper, we investigate sulfur chemistry in laboratory analogs of Jupiter Trojans and Kuiper Belt Objects (KBOs). Electron irradiation experiments of CH_3OH–NH_3–H_2O and H_2S–CH_3OH–NH_3–H_2O ices were conducted to better understand the chemical differences between primordial planetesimals inside and outside the sublimation line of H_2S. The main goal of this work is to test the chemical plausibility of the hypothesis correlating the color bimodality in Jupiter Trojans with sulfur chemistry in the incipient solar system. Temperature programmed desorption (TPD) of the irradiated mixtures allows the detection of small sulfur allotropes (S_3 and S_4) after the irradiation of H2S containing ice...

  6. Electronic environments of ferrous iron in rhyolitic and basaltic glasses at high pressure

    Solomatova, Natalia V.; Jackson, Jennifer M.; Sturhahn, Wolfgang; Rossman, George R.; Roskosz, Mathieu
    The physical properties of silicate melts within Earth's mantle affect the chemical and thermal evolution of its interior. Chemistry and coordination environments affect such properties. We have measured the hyperfine parameters of iron-bearing rhyolitic and basaltic glasses up to ~120 GPa and ~100 GPa, respectively, in a neon pressure medium using time domain synchrotron Mössbauer spectroscopy. The spectra for rhyolitic and basaltic glasses are well explained by three high-spin Fe^(2+)-like sites with distinct quadrupole splittings. Absence of detectable ferric iron was confirmed with optical absorption spectroscopy. The sites with relatively high and intermediate quadrupole splittings are likely a result of...

  7. Electronic environments of ferrous iron in rhyolitic and basaltic glasses at high pressure

    Solomatova, Natalia V.; Jackson, Jennifer M.; Sturhahn, Wolfgang; Rossman, George R.; Roskosz, Mathieu
    The physical properties of silicate melts within Earth's mantle affect the chemical and thermal evolution of its interior. Chemistry and coordination environments affect such properties. We have measured the hyperfine parameters of iron-bearing rhyolitic and basaltic glasses up to ~120 GPa and ~100 GPa, respectively, in a neon pressure medium using time domain synchrotron Mössbauer spectroscopy. The spectra for rhyolitic and basaltic glasses are well explained by three high-spin Fe^(2+)-like sites with distinct quadrupole splittings. Absence of detectable ferric iron was confirmed with optical absorption spectroscopy. The sites with relatively high and intermediate quadrupole splittings are likely a result of...

  8. Methane emissions from dairies in the Los Angeles Basin

    Viatte, Camille; Lauvaux, Thomas; Hedelius, Jacob K.; Parker, Harrison; Chen, Jia; Jones, Taylor; Franklin, Jonathan E.; Deng, Aijun J.; Gaudet, Brian; Verhulst, Kristal; Duren, Riley; Wunch, Debra; Roehl, Coleen; Dubey, Manvendra K.; Wofsy, Steven; Wennberg, Paul O.
    We estimate the amount of methane (CH_4) emitted by the largest dairies in the southern California region by combining measurements from four mobile solar-viewing ground-based spectrometers (EM27/SUN), in situ isotopic ^(13∕12)CH_4 measurements from a CRDS analyzer (Picarro), and a high-resolution atmospheric transport simulation with a Weather Research and Forecasting model in large-eddy simulation mode (WRF-LES). The remote sensing spectrometers measure the total column-averaged dry-air mole fractions of CH_4 and CO_2 (X_(CH)_4 and X_(CO)_2) in the near infrared region, providing information on total emissions of the dairies at Chino. Differences measured between the four EM27/SUN ranged from 0.2 to 22 ppb (part...

  9. Methane emissions from dairies in the Los Angeles Basin

    Viatte, Camille; Lauvaux, Thomas; Hedelius, Jacob K.; Parker, Harrison; Chen, Jia; Jones, Taylor; Franklin, Jonathan E.; Deng, Aijun J.; Gaudet, Brian; Verhulst, Kristal; Duren, Riley; Wunch, Debra; Roehl, Coleen; Dubey, Manvendra K.; Wofsy, Steven; Wennberg, Paul O.
    We estimate the amount of methane (CH_4) emitted by the largest dairies in the southern California region by combining measurements from four mobile solar-viewing ground-based spectrometers (EM27/SUN), in situ isotopic ^(13∕12)CH_4 measurements from a CRDS analyzer (Picarro), and a high-resolution atmospheric transport simulation with a Weather Research and Forecasting model in large-eddy simulation mode (WRF-LES). The remote sensing spectrometers measure the total column-averaged dry-air mole fractions of CH_4 and CO_2 (X_(CH)_4 and X_(CO)_2) in the near infrared region, providing information on total emissions of the dairies at Chino. Differences measured between the four EM27/SUN ranged from 0.2 to 22 ppb (part...

  10. Empirically Derived Sensitivity of Vegetation to Climate across Global Gradients of Temperature and Precipitation

    Quetin, Gregory R.; Swann, Abigail
    The natural composition of terrestrial ecosystems can be shaped by climate to take advantage of local environmental conditions. Ecosystem functioning (e.g., interaction between photosynthesis and temperature) can also acclimate to different climatological states. The combination of these two factors thus determines ecological–climate interactions. A global empirical map of the sensitivity of vegetation to climate is derived using the response of satellite-observed greenness to interannual variations in temperature and precipitation. Mechanisms constraining ecosystem functioning are inferred by analyzing how the sensitivity of vegetation to climate varies across climate space. Analysis yields empirical evidence for multiple physical and biological mediators of the...

  11. Methane Seepage on Mars: Where to Look and Why

    Oehler, Dorothy Z.; Etiope, Giuseppe
    Methane on Mars is a topic of special interest because of its potential association with microbial life. The variable detections of methane by the Curiosity rover, orbiters, and terrestrial telescopes, coupled with methane's short lifetime in the martian atmosphere, may imply an active gas source in the planet's subsurface, with migration and surface emission processes similar to those known on Earth as “gas seepage.” Here, we review the variety of subsurface processes that could result in methane seepage on Mars. Such methane could originate from abiotic chemical reactions, thermogenic alteration of abiotic or biotic organic matter, and ancient or extant...

  12. Easily fabricated ion source for characterizing mixtures of organic compounds by direct analysis in real time mass spectrometry

    Upton, Kathleen T.; Schilling, Katherine A.; Beauchamp, J. L.
    The increasing use of atmospheric pressure mass spectrometry has led to the development of many ambient ionization sources, for which sampling versatility and low cost are desired features. One such recent ambient ionization method is direct analysis in real time mass spectrometry (DART-MS), which has proven to be well suited to the analysis of native samples of both simple and complex natures. We describe a home-built DART source (EZ-DART) with versatile sampling capabilities, low power requirements, and low assembly cost which can be easily interfaced to mass spectrometers equipped with an atmospheric pressure inlet. The operating temperature range (22–250 °C)...

  13. Easily fabricated ion source for characterizing mixtures of organic compounds by direct analysis in real time mass spectrometry

    Upton, Kathleen T.; Schilling, Katherine A.; Beauchamp, J. L.
    The increasing use of atmospheric pressure mass spectrometry has led to the development of many ambient ionization sources, for which sampling versatility and low cost are desired features. One such recent ambient ionization method is direct analysis in real time mass spectrometry (DART-MS), which has proven to be well suited to the analysis of native samples of both simple and complex natures. We describe a home-built DART source (EZ-DART) with versatile sampling capabilities, low power requirements, and low assembly cost which can be easily interfaced to mass spectrometers equipped with an atmospheric pressure inlet. The operating temperature range (22–250 °C)...

  14. Easily fabricated ion source for characterizing mixtures of organic compounds by direct analysis in real time mass spectrometry

    Upton, Kathleen T.; Schilling, Katherine A.; Beauchamp, J. L.
    The increasing use of atmospheric pressure mass spectrometry has led to the development of many ambient ionization sources, for which sampling versatility and low cost are desired features. One such recent ambient ionization method is direct analysis in real time mass spectrometry (DART-MS), which has proven to be well suited to the analysis of native samples of both simple and complex natures. We describe a home-built DART source (EZ-DART) with versatile sampling capabilities, low power requirements, and low assembly cost which can be easily interfaced to mass spectrometers equipped with an atmospheric pressure inlet. The operating temperature range (22–250 °C)...

  15. Emissions and topographic effects on column CO_2 (XCO_2) variations, with a focus on the Southern California Megacity

    Hedelius, Jacob K.; Feng, Sha; Roehl, Coleen M.; Wunch, Debra; Hillyard, Patrick W.; Podolske, James R.; Iraci, Laura T.; Patarasuk, Risa; Rao, Preeti; O'Keeffe, Darragh; Gurney, Kevin R.; Lauvaux, Thomas; Wennberg, Paul O.
    Within the California South Coast Air Basin (SoCAB), X_(CO)_2 varies significantly due to atmospheric dynamics and the nonuniform distribution of sources. X_(CO)_2 measurements within the basin have seasonal variation compared to the “background” due primarily to dynamics, or the origins of air masses coming into the basin. We observe basin-background differences that are in close agreement for three observing systems: Total Carbon Column Observing Network (TCCON) 2.3 ± 1.2 ppm, Orbiting Carbon Observatory-2 (OCO-2) 2.4 ± 1.5 ppm, and Greenhouse gases Observing Satellite 2.4 ± 1.6 ppm (errors are 1σ). We further observe persistent significant differences (∼0.9 ppm) in X_(CO)_2...

  16. Emissions and topographic effects on column CO_2 (XCO_2) variations, with a focus on the Southern California Megacity

    Hedelius, Jacob K.; Feng, Sha; Roehl, Coleen M.; Wunch, Debra; Hillyard, Patrick W.; Podolske, James R.; Iraci, Laura T.; Patarasuk, Risa; Rao, Preeti; O'Keeffe, Darragh; Gurney, Kevin R.; Lauvaux, Thomas; Wennberg, Paul O.
    Within the California South Coast Air Basin (SoCAB), X_(CO)_2 varies significantly due to atmospheric dynamics and the nonuniform distribution of sources. X_(CO)_2 measurements within the basin have seasonal variation compared to the “background” due primarily to dynamics, or the origins of air masses coming into the basin. We observe basin-background differences that are in close agreement for three observing systems: Total Carbon Column Observing Network (TCCON) 2.3 ± 1.2 ppm, Orbiting Carbon Observatory-2 (OCO-2) 2.4 ± 1.5 ppm, and Greenhouse gases Observing Satellite 2.4 ± 1.6 ppm (errors are 1σ). We further observe persistent significant differences (∼0.9 ppm) in X_(CO)_2...

  17. Emissions and topographic effects on column CO_2 (XCO_2) variations, with a focus on the Southern California Megacity

    Hedelius, Jacob K.; Feng, Sha; Roehl, Coleen M.; Wunch, Debra; Hillyard, Patrick W.; Podolske, James R.; Iraci, Laura T.; Patarasuk, Risa; Rao, Preeti; O'Keeffe, Darragh; Gurney, Kevin R.; Lauvaux, Thomas; Wennberg, Paul O.
    Within the California South Coast Air Basin (SoCAB), X_(CO)_2 varies significantly due to atmospheric dynamics and the nonuniform distribution of sources. X_(CO)_2 measurements within the basin have seasonal variation compared to the “background” due primarily to dynamics, or the origins of air masses coming into the basin. We observe basin-background differences that are in close agreement for three observing systems: Total Carbon Column Observing Network (TCCON) 2.3 ± 1.2 ppm, Orbiting Carbon Observatory-2 (OCO-2) 2.4 ± 1.5 ppm, and Greenhouse gases Observing Satellite 2.4 ± 1.6 ppm (errors are 1σ). We further observe persistent significant differences (∼0.9 ppm) in X_(CO)_2...

  18. Connecting active to passive fluorescence with photosynthesis: a method for evaluating remote sensing measurements of Chl fluorescence

    Magney, Troy S.; Frankenberg, Christian; Fisher, Joshua B.; Sun, Ying; North, Gretchen B.; Davis, Thomas S.; Kornfeld, Ari; Siebke, Katharina
    Recent advances in the retrieval of Chl fluorescence from space using passive methods (solar-induced Chl fluorescence, SIF) promise improved mapping of plant photosynthesis globally. However, unresolved issues related to the spatial, spectral, and temporal dynamics of vegetation fluorescence complicate our ability to interpret SIF measurements. We developed an instrument to measure leaf-level gas exchange simultaneously with pulse-amplitude modulation (PAM) and spectrally resolved fluorescence over the same field of view – allowing us to investigate the relationships between active and passive fluorescence with photosynthesis. Strongly correlated, slope-dependent relationships were observed between measured spectra across all wavelengths (Fλ, 670–850 nm) and PAM fluorescence parameters...

  19. Constraining the Origin of the Jupiter Trojans by In Situ Measurement of Volatiles, Minerals, and Ices

    Blacksberg, Jordana; Eiler, John M.
    As the KISS Trojans program comes to a close, we report here on our achievements in this venture that began with a KISS workshop in 2012, “In Situ Science and Instrumentation for Primitive Bodies”. The original workshop brought together a diverse group (see Appendix B) that set out to tackle an ambitious goal – to find a way to test predictions of dynamical models (such as the Nice model, named after the founding research group in Nice, France), that have recently led to a radically new understanding of solar system formation. We aimed to do so through interdisciplinary collaboration between...

  20. Exploration telepresence: A strategy for optimizing scientific research at remote space destinations

    Lester, Dan; Hodges, Kip; Anderson, Robert C.
    Modern telerobotic technologies offer astronaut scientists real-time presence on planetary surfaces without the risk and cost of putting them all the way there.

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