Templeton Alexis S.

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Alexis S.

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  • Article
    Vailulu'u Seamount, Samoa : life and death on an active submarine volcano
    (National Academy of Sciences, 2006-04-13) Staudigel, Hubert ; Hart, Stanley R. ; Pile, Adele ; Bailey, Bradley E. ; Baker, Edward T. ; Brooke, Sandra ; Connelly, Douglas P. ; Haucke, Lisa ; German, Christopher R. ; Hudson, Ian ; Jones, Daniel O. B. ; Koppers, Anthony A. P. ; Konter, Jasper G. ; Lee, Ray ; Pietsch, Theodore W. ; Tebo, Bradley M. ; Templeton, Alexis S. ; Zierenberg, Robert ; Young, Craig M.
    Submersible exploration of the Samoan hotspot revealed a new, 300-m-tall, volcanic cone, named Nafanua, in the summit crater of Vailulu'u seamount. Nafanua grew from the 1,000-m-deep crater floor in <4 years and could reach the sea surface within decades. Vents fill Vailulu'u crater with a thick suspension of particulates and apparently toxic fluids that mix with seawater entering from the crater breaches. Low-temperature vents form Fe oxide chimneys in many locations and up to 1-m-thick layers of hydrothermal Fe floc on Nafanua. High-temperature (81°C) hydrothermal vents in the northern moat (945-m water depth) produce acidic fluids (pH 2.7) with rising droplets of (probably) liquid CO2. The Nafanua summit vent area is inhabited by a thriving population of eels (Dysommina rugosa) that feed on midwater shrimp probably concentrated by anticyclonic currents at the volcano summit and rim. The moat and crater floor around the new volcano are littered with dead metazoans that apparently died from exposure to hydrothermal emissions. Acid-tolerant polychaetes (Polynoidae) live in this environment, apparently feeding on bacteria from decaying fish carcasses. Vailulu'u is an unpredictable and very active underwater volcano presenting a potential long-term volcanic hazard. Although eels thrive in hydrothermal vents at the summit of Nafanua, venting elsewhere in the crater causes mass mortality. Paradoxically, the same anticyclonic currents that deliver food to the eels may also concentrate a wide variety of nektonic animals in a death trap of toxic hydrothermal fluids.
  • Article
    Hydrogen generation and iron partitioning during experimental serpentinization of an olivine-pyroxene mixture
    (Elsevier, 2020-05-26) McCollom, Thomas M. ; Klein, Frieder ; Moskowitz, Bruce ; Berquo, Thelma S. ; Bach, Wolfgang ; Templeton, Alexis S.
    A series of laboratory experiments was conducted to investigate serpentinization of olivine–pyroxene mixtures at 230 °C, with the objective of evaluating the effect of mixed compositions on Fe partitioning among product minerals, H2 generation, and reaction rates. An initial experiment reacted a mixture of 86 wt.% olivine and 14 wt.% orthopyroxene (Opx) with the same initial grain size for 387 days. The experiment resulted in extensive reaction (∼53% conversion), and solids recovered at termination of the experiment were dominated by Fe-bearing chrysotile and relict olivine along with minor brucite and magnetite. Only limited amounts of H2 were generated during the first ∼100 days of the experiment, but the rate of H2 generation then increased sharply coincident with an increase in pH from mildly alkaline to strongly alkaline conditions. Two shorter term experiments with the same reactants (26 and 113 days) produced a mixture of lizardite and talc that formed a thin coating on relict olivine and Opx grains, with virtually no generation of H2. Comparison of the results with reaction path models indicates that the Opx reacted about two times faster than olivine, which contrasts with some previous studies that suggested olivine should react more rapidly than Opx at the experimental conditions. The models also indicate that the long-term experiment transitioned from producing serpentine ± talc early in the early stages to precipitation of serpentine plus magnetite, with brucite beginning to precipitate only late in the experiment as Opx was depleted. The results indicate that overall reaction of olivine and Opx was initially relatively slow, but reaction rates accelerated substantially when the pH transitioned to strongly alkaline conditions. Serpentine and brucite precipitated from the olivine-Opx mixture had higher Fe contents than observed in olivine-only experiments at mildly alkaline pH, but had comparable Fe contents to reaction of olivine at strongly alkaline pH implying that higher pH may favor greater partitioning of Fe into serpentine and brucite and less into magnetite. Despite the presence of brucite, dissolved silica activities during the long-term olivine-Opx experiment maintained levels well above serpentine-brucite equilibrium. Instead, silica activities converged on levels close to metastable equilibrium between brucite and olivine. It is proposed that silica levels during the experiment may have been regulated by exchange of SiO2 between the fluid and a silica-depleted, brucite-like surface layer on dissolving olivine.
  • Article
    Science goals and mission architecture of the Europa Lander mission concept
    (IOP Publishing, 2022-01-26) Hand, Kevin P. ; Phillips, Cynthia B. ; Murray, Alison E. ; Garvin, James B. ; Maize, Earl H. ; Gibbs, Roger G. ; Reeves, Glenn ; San Martin, A. Miguel ; Tan-Wang, Grace H. ; Krajewski, Joel ; Hurst, Kenneth ; Crum, Ray ; Kennedy, Brett A. ; McElrath, Timothy P. ; Gallon, John C. ; Sabahi, Dara ; Thurman, Sam W. ; Goldstein, Barry ; Estabrook, Polly ; Lee, Steven W. ; Dooley, Jennifer A. ; Brinckerhoff, William B. ; Edgett, Kenneth S. ; German, Christopher R. ; Hoehler, Tori M. ; Hörst, Sarah M. ; Lunine, Jonathan I. ; Paranicas, Christopher ; Nealson, Kenneth H. ; Smith, David E. ; Templeton, Alexis S. ; Russell, Michael J. ; Schmidt, Britney E. ; Christner, Brent C. ; Ehlmann, Bethany L. ; Hayes, Alexander ; Rhoden, Alyssa R. ; Willis, Peter ; Yingst, R. Aileen ; Craft, Kathleen L. ; Cameron, Marissa E. ; Nordheim, Tom A. ; Pitesky, Jo ; Scully, Jennifer ; Hofgartner, Jason D. ; Sell, Steve W. ; Barltrop, Kevin J. ; Izraelevitz, Jacob ; Brandon, Erik J. ; Seong, J. ; Jones, John-Paul ; Pasalic, Jasmina ; Billings, Keith J. ; Ruiz, John Paul ; Bugga, Ratnakumar V. ; Graham, Dan ; Arenas, L. A. ; Takeyama, Deidre ; Drummond, Mai ; Aghazarian, Hrand ; Andersen, Allen J. ; Andersen, Kayla B. ; Anderson, E. W. ; Babuscia, Alessandra ; Backes, Paul G. ; Bailey, Elizabeth S. ; Balentine, Daniel ; Ballard, Christopher G. ; Berisford, Daniel F. ; Bhandari, Pradeep ; Blackwood, Krys ; Bolotin, Gary S. ; Bovre, Emilee A. ; Bowkett, Joseph ; Boykins, Kobie T. ; Bramble, Michael S. ; Brice, Timothy M. ; Briggs, Paul ; Brinkman, Alexander P. ; Brooks, Shawn M. ; Buffington, Brent B. ; Burns, Brandon ; Cable, Morgan L. ; Campagnola,Stefano ; Cangahuala, Laureano A. ; Carr, Gregory A. ; Casani, John R. ; Chahat, Nacer E. ; Chamberlain-Simon, Brendan K. ; Cheng, Yun-Ting ; Chien, Steve A. ; Cook, B. T. ; Cooper, Moogega ; Dinicola, Michael ; Clement, Brian G. ; Dean, Zachary S. ; Cullimore, Emily A. ; Curtis, Aaron G. ; de la Croix, Jean-Pierre ; Di Pasquale, Peter ; Dodd, Emma M. ; Dubord, Luke A. ; Edlund, Jeffrey A. ; Ellyin, Raymond ; Emanuel, Blair ; Foster, Jeffrey T. ; Ganino, Anthony J. ; Garner, Gregory J. ; Gibson, Matt T. ; Gildner, Matt ; Glazebrook, Kenneth J. ; Greco, Martin E. ; Green, W. M. ; Hatch, Sara J. ; Hetzel, Mark M. ; Hoey, William A. ; Hofmann, Amy E. ; Ionasescu, Rodica ; Jain, Abhinandan ; Jasper, Jay D. ; Johannesen, Jennie R. ; Johnson, Glenn K. ; Jun, Insoo ; Katake, Anup B. ; Kim-Castet, So Young ; Kim, David Inkyu ; Kim, Wousik ; Klonicki, Emily F. ; Kobeissi, Brad ; Kobie, Bryan D. ; Kochocki, Joseph ; Kokorowski, Michael ; Kosberg, Jacob A. ; Kriechbaum, Kristopher ; Kulkarni, Tejas P. ; Lam, Rebekah L. ; Landau, Damon F. ; Lattimore, Myra A. ; Laubach, Sharon L. ; Lawler, Christopher R. ; Lim, Grace ; Li, Jui-Lin ; Litwin, Todd E. ; Lo, Martin W. ; Logan, Cambria A. ; Maghasoudi, Elham ; Mandrake, Lukas ; Marchetti, Yuliya ; Marteau, Eloise ; Maxwell, Kimberly A. ; McNamee, John B. ; McIntyre, Ocean ; Meacham, Michael ; Melko, Joseph P. ; Mueller, Juergen ; Muliere, David ; Mysore, Aprameya ; Nash, Jeremy ; Ono, Masahiro ; Parker, Jay M. ; Perkins, Rebecca C. ; Petropoulos, Anastassios E. ; Gaut, Aaron ; Piette Gomez, Marie Y. ; Casillas, Raul Polit ; Preudhomme, Michael ; Pyrzak, Guy ; Rapinchuk, Jacqueline ; Ratliff, John Martin ; Ray, T. L. ; Roberts, Eric T. ; Roffo, Kenneth ; Roth, Duane C. ; Russino, Joseph A. ; Schmidt, Tyler M. ; Schoppers, Marcel J. ; Senent, Juan S. ; Serricchio, Fred ; Sheldon, Douglas J. ; Shiraishi, Lori R. ; Shirvanian, James ; Siegel, Katherine J. ; Singh, Gurjeet ; Sirota, Allen R. ; Skulsky, Eli D. ; Stehly, Joseph S. ; Strange, Nathan J. ; Stevens, Sarah U. ; Sunada, Eric T. ; Tepsuporn, Scott P. ; Tosi, Luis Phillipe C. ; Trawny, Nikolas ; Uchenik, Igor ; Verma, Vandi ; Volpe, Richard A. ; Wagner, Caleb T. ; Wang, D. ; Willson, Reg G. ; Wolff, John Luke ; Wong, A. T. ; Zimmer, Aline K. ; Sukhatme, Kalyani G. ; Bago, Kevin A. ; Chen, Yang ; Deardorff, Alyssa M. ; Kuch, Roger S. ; Lim, Christopher ; Syvertson, Marguerite L. ; Arakaki, Genji A. ; Avila, Art ; DeBruin, Kevin J. ; Frick, Andreas ; Harris, Joby R. ; Heverly, Matthew C. ; Kawata, Jessie M. ; Kim‬, Sung-Kyun ; Kipp, Devin M. ; Murphy, Juliana ; Smith, Matthew W. ; Spaulding, Matthew D. ; Thakker, Rohan ; Warner, Noah Z. ; Yahnker, Chris R. ; Young, M. E. ; Magner, Tom ; Adams, Danica ; Bedini, Peter ; Mehr, Lauren ; Sheldon, Colin ; Vernon, Steven ; Bailey, Vince ; Briere, Marc ; Butler, Michael ; Davis, Amanda ; Ensor, Susan ; Gannon, Michele ; Haapala-Chalk, Amanda ; Hartka, Ted ; Holdridge, Mark ; Hong, Albert ; Hunt, J. ; Iskow, Joe ; Kahler, Faith ; Murray, Kimberly ; Napolillo, David ; Norkus, Michael ; Pfisterer, Rick ; Porter, Jamie ; Roth, David ; Schwartz, Paul ; Wolfarth, Lawrence ; Cardiff, Eric ; Davis, Anita ; Grob, Eric W. ; Adam, Jason R. ; Betts, Erin ; Norwood, Jason ; Heller, M. M. ; Voskuilen, Tyler ; Sakievich, Philip ; Gray, L. ; Hansen, D. J. ; Irick, Kevin W. ; Hewson, John C. ; Lamb, Joshua ; Stacy, S. C. ; Brotherton, Chris M. ; Tappan, Alexander S. ; Benally, Darryl ; Thigpen, Hannah ; Ortiz, Erick ; Sandoval, Dan ; Ison, Aaron M. ; Warren, M. ; Stromberg, Peter G. ; Thelen, Paul Mark ; Blasy, B. ; Nandy, Prabal ; Haddad, Alexandria W. ; Trujillo, Lynna B. ; Wiseley, T. H. ; Bell, S. A. ; Teske, Nicholas P. ; Post, C. ; Torres-Castro, Loraine ; Grosso, Chris ; Wasiolek, Maryla
    Europa is a premier target for advancing both planetary science and astrobiology, as well as for opening a new window into the burgeoning field of comparative oceanography. The potentially habitable subsurface ocean of Europa may harbor life, and the globally young and comparatively thin ice shell of Europa may contain biosignatures that are readily accessible to a surface lander. Europa's icy shell also offers the opportunity to study tectonics and geologic cycles across a range of mechanisms and compositions. Here we detail the goals and mission architecture of the Europa Lander mission concept, as developed from 2015 through 2020. The science was developed by the 2016 Europa Lander Science Definition Team (SDT), and the mission architecture was developed by the preproject engineering team, in close collaboration with the SDT. In 2017 and 2018, the mission concept passed its mission concept review and delta-mission concept review, respectively. Since that time, the preproject has been advancing the technologies, and developing the hardware and software, needed to retire risks associated with technology, science, cost, and schedule.