ALBERT

Description: Changes in the mechanisms of formation and global distribution of phyllosilicate clay minerals through 4.567 Ga of planetary evolution in our solar system reflect evolving tectonic, geochemical, and biological processes. Clay minerals were absent prior to planetesimal formation ~4.6 billion years ago but today are abundant in all near-surface Earth environments. New clay mineral species and modes of clay mineral paragenesis occurred as a consequence of major events in Earth’s evolution—notably the formation of a mafic crust and oceans, the emergence of granite-rooted continents, the initiation of plate tectonics and subduction, the Great Oxidation Event, and the rise of the terrestrial biosphere. The changing character of clay minerals through time is thus an important part of Earth’s mineralogical history and exemplifies the principles of mineral evolution.

Description: Stable isotope ratios of H, C, and O are powerful indicators of a wide variety of planetary geophysical processes, and for Mars they reveal the record of loss of its atmosphere and subsequent interactions with its surface such as carbonate formation. We report in situ measurements of the isotopic ratios of D/H and (18)O/(16)O in water and (13)C/(12)C, (18)O/(16)O, (17)O/(16)O, and (13)C(18)O/(12)C(16)O in carbon dioxide, made in the martian atmosphere at Gale Crater from the Curiosity rover using the Sample Analysis at Mars (SAM)'s tunable laser spectrometer (TLS). Comparison between our measurements in the modern atmosphere and those of martian meteorites such as ALH 84001 implies that the martian reservoirs of CO2 and H2O were largely established ~4 billion years ago, but that atmospheric loss or surface interaction may be still ongoing.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Webster, Chris R -- Mahaffy, Paul R -- Flesch, Gregory J -- Niles, Paul B -- Jones, John H -- Leshin, Laurie A -- Atreya, Sushil K -- Stern, Jennifer C -- Christensen, Lance E -- Owen, Tobias -- Franz, Heather -- Pepin, Robert O -- Steele, Andrew -- MSL Science Team -- Achilles, Cherie -- Agard, Christophe -- Alves Verdasca, Jose Alexandre -- Anderson, Robert -- Anderson, Ryan -- Archer, Doug -- Armiens-Aparicio, Carlos -- Arvidson, Ray -- Atlaskin, Evgeny -- Aubrey, Andrew -- Baker, Burt -- Baker, Michael -- Balic-Zunic, Tonci -- Baratoux, David -- Baroukh, Julien -- Barraclough, Bruce -- Bean, Keri -- Beegle, Luther -- Behar, Alberto -- Bell, James -- Bender, Steve -- Benna, Mehdi -- Bentz, Jennifer -- Berger, Gilles -- Berger, Jeff -- Berman, Daniel -- Bish, David -- Blake, David F -- Blanco Avalos, Juan J -- Blaney, Diana -- Blank, Jen -- Blau, Hannah -- Bleacher, Lora -- Boehm, Eckart -- Botta, Oliver -- Bottcher, Stephan -- Boucher, Thomas -- Bower, Hannah -- Boyd, Nick -- Boynton, Bill -- Breves, Elly -- Bridges, John -- Bridges, Nathan -- Brinckerhoff, William -- Brinza, David -- Bristow, Thomas -- Brunet, Claude -- Brunner, Anna -- Brunner, Will -- Buch, Arnaud -- Bullock, Mark -- Burmeister, Sonke -- Cabane, Michel -- Calef, Fred -- Cameron, James -- Campbell, John -- Cantor, Bruce -- Caplinger, Michael -- Caride Rodriguez, Javier -- Carmosino, Marco -- Carrasco Blazquez, Isaias -- Charpentier, Antoine -- Chipera, Steve -- Choi, David -- Clark, Benton -- Clegg, Sam -- Cleghorn, Timothy -- Cloutis, Ed -- Cody, George -- Coll, Patrice -- Conrad, Pamela -- Coscia, David -- Cousin, Agnes -- Cremers, David -- Crisp, Joy -- Cros, Alain -- Cucinotta, Frank -- d'Uston, Claude -- Davis, Scott -- Day, Mackenzie -- de la Torre Juarez, Manuel -- DeFlores, Lauren -- DeLapp, Dorothea -- DeMarines, Julia -- DesMarais, David -- Dietrich, William -- Dingler, Robert -- Donny, Christophe -- Downs, Bob -- Drake, Darrell -- Dromart, Gilles -- Dupont, Audrey -- Duston, Brian -- Dworkin, Jason -- Dyar, M Darby -- Edgar, Lauren -- Edgett, Kenneth -- Edwards, Christopher -- Edwards, Laurence -- Ehlmann, Bethany -- Ehresmann, Bent -- Eigenbrode, Jen -- Elliott, Beverley -- Elliott, Harvey -- Ewing, Ryan -- Fabre, Cecile -- Fairen, Alberto -- Farley, Ken -- Farmer, Jack -- Fassett, Caleb -- Favot, Laurent -- Fay, Donald -- Fedosov, Fedor -- Feldman, Jason -- Feldman, Sabrina -- Fisk, Marty -- Fitzgibbon, Mike -- Floyd, Melissa -- Fluckiger, Lorenzo -- Forni, Olivier -- Fraeman, Abby -- Francis, Raymond -- Francois, Pascaline -- Freissinet, Caroline -- French, Katherine Louise -- Frydenvang, Jens -- Gaboriaud, Alain -- Gailhanou, Marc -- Garvin, James -- Gasnault, Olivier -- Geffroy, Claude -- Gellert, Ralf -- Genzer, Maria -- Glavin, Daniel -- Godber, Austin -- Goesmann, Fred -- Goetz, Walter -- Golovin, Dmitry -- Gomez Gomez, Felipe -- Gomez-Elvira, Javier -- Gondet, Brigitte -- Gordon, Suzanne -- Gorevan, Stephen -- Grant, John -- Griffes, Jennifer -- Grinspoon, David -- Grotzinger, John -- Guillemot, Philippe -- Guo, Jingnan -- Gupta, Sanjeev -- Guzewich, Scott -- Haberle, Robert -- Halleaux, Douglas -- Hallet, Bernard -- Hamilton, Vicky -- Hardgrove, Craig -- Harker, David -- Harpold, Daniel -- Harri, Ari-Matti -- Harshman, Karl -- Hassler, Donald -- Haukka, Harri -- Hayes, Alex -- Herkenhoff, Ken -- Herrera, Paul -- Hettrich, Sebastian -- Heydari, Ezat -- Hipkin, Victoria -- Hoehler, Tori -- Hollingsworth, Jeff -- Hudgins, Judy -- Huntress, Wesley -- Hurowitz, Joel -- Hviid, Stubbe -- Iagnemma, Karl -- Indyk, Steve -- Israel, Guy -- Jackson, Ryan -- Jacob, Samantha -- Jakosky, Bruce -- Jensen, Elsa -- Jensen, Jaqueline Klovgaard -- Johnson, Jeffrey -- Johnson, Micah -- Johnstone, Steve -- Jones, Andrea -- Joseph, Jonathan -- Jun, Insoo -- Kah, Linda -- Kahanpaa, Henrik -- Kahre, Melinda -- Karpushkina, Natalya -- Kasprzak, Wayne -- Kauhanen, Janne -- Keely, Leslie -- Kemppinen, Osku -- Keymeulen, Didier -- Kim, Myung-Hee -- Kinch, Kjartan -- King, Penny -- Kirkland, Laurel -- Kocurek, Gary -- Koefoed, Asmus -- Kohler, Jan -- Kortmann, Onno -- Kozyrev, Alexander -- Krezoski, Jill -- Krysak, Daniel -- Kuzmin, Ruslan -- Lacour, Jean Luc -- Lafaille, Vivian -- Langevin, Yves -- Lanza, Nina -- Lasue, Jeremie -- Le Mouelic, Stephane -- Lee, Ella Mae -- Lee, Qiu-Mei -- Lees, David -- Lefavor, Matthew -- Lemmon, Mark -- Lepinette Malvitte, Alain -- Leveille, Richard -- Lewin-Carpintier, Eric -- Lewis, Kevin -- Li, Shuai -- Lipkaman, Leslie -- Little, Cynthia -- Litvak, Maxim -- Lorigny, Eric -- Lugmair, Guenter -- Lundberg, Angela -- Lyness, Eric -- Madsen, Morten -- Maki, Justin -- Malakhov, Alexey -- Malespin, Charles -- Malin, Michael -- Mangold, Nicolas -- Manhes, Gerard -- Manning, Heidi -- Marchand, Genevieve -- Marin Jimenez, Mercedes -- Martin Garcia, Cesar -- Martin, Dave -- Martin, Mildred -- Martinez-Frias, Jesus -- Martin-Soler, Javier -- Martin-Torres, F Javier -- Mauchien, Patrick -- Maurice, Sylvestre -- McAdam, Amy -- McCartney, Elaina -- McConnochie, Timothy -- McCullough, Emily -- McEwan, Ian -- McKay, Christopher -- McLennan, Scott -- McNair, Sean -- Melikechi, Noureddine -- Meslin, Pierre-Yves -- Meyer, Michael -- Mezzacappa, Alissa -- Miller, Hayden -- Miller, Kristen -- Milliken, Ralph -- Ming, Douglas -- Minitti, Michelle -- Mischna, Michael -- Mitrofanov, Igor -- Moersch, Jeff -- Mokrousov, Maxim -- Molina Jurado, Antonio -- Moores, John -- Mora-Sotomayor, Luis -- Morookian, John Michael -- Morris, Richard -- Morrison, Shaunna -- Mueller-Mellin, Reinhold -- Muller, Jan-Peter -- Munoz Caro, Guillermo -- Nachon, Marion -- Navarro Lopez, Sara -- Navarro-Gonzalez, Rafael -- Nealson, Kenneth -- Nefian, Ara -- Nelson, Tony -- Newcombe, Megan -- Newman, Claire -- Newsom, Horton -- Nikiforov, Sergey -- Nixon, Brian -- Noe Dobrea, Eldar -- Nolan, Thomas -- Oehler, Dorothy -- Ollila, Ann -- Olson, Timothy -- de Pablo Hernandez, Miguel Angel -- Paillet, Alexis -- Pallier, Etienne -- Palucis, Marisa -- Parker, Timothy -- Parot, Yann -- Patel, Kiran -- Paton, Mark -- Paulsen, Gale -- Pavlov, Alex -- Pavri, Betina -- Peinado-Gonzalez, Veronica -- Peret, Laurent -- Perez, Rene -- Perrett, Glynis -- Peterson, Joe -- Pilorget, Cedric -- Pinet, Patrick -- Pla-Garcia, Jorge -- Plante, Ianik -- Poitrasson, Franck -- Polkko, Jouni -- Popa, Radu -- Posiolova, Liliya -- Posner, Arik -- Pradler, Irina -- Prats, Benito -- Prokhorov, Vasily -- Purdy, Sharon Wilson -- Raaen, Eric -- Radziemski, Leon -- Rafkin, Scot -- Ramos, Miguel -- Rampe, Elizabeth -- Raulin, Francois -- Ravine, Michael -- Reitz, Gunther -- Renno, Nilton -- Rice, Melissa -- Richardson, Mark -- Robert, Francois -- Robertson, Kevin -- Rodriguez Manfredi, Jose Antonio -- Romeral-Planello, Julio J -- Rowland, Scott -- Rubin, David -- Saccoccio, Muriel -- Salamon, Andrew -- Sandoval, Jennifer -- Sanin, Anton -- Sans Fuentes, Sara Alejandra -- Saper, Lee -- Sarrazin, Philippe -- Sautter, Violaine -- Savijarvi, Hannu -- Schieber, Juergen -- Schmidt, Mariek -- Schmidt, Walter -- Scholes, Daniel -- Schoppers, Marcel -- Schroder, Susanne -- Schwenzer, Susanne -- Sebastian Martinez, Eduardo -- Sengstacken, Aaron -- Shterts, Ruslan -- Siebach, Kirsten -- Siili, Tero -- Simmonds, Jeff -- Sirven, Jean-Baptiste -- Slavney, Susie -- Sletten, Ronald -- Smith, Michael -- Sobron Sanchez, Pablo -- Spanovich, Nicole -- Spray, John -- Squyres, Steven -- Stack, Katie -- Stalport, Fabien -- Stein, Thomas -- Stewart, Noel -- Stipp, Susan Louise Svane -- Stoiber, Kevin -- Stolper, Ed -- Sucharski, Bob -- Sullivan, Rob -- Summons, Roger -- Sumner, Dawn -- Sun, Vivian -- Supulver, Kimberley -- Sutter, Brad -- Szopa, Cyril -- Tan, Florence -- Tate, Christopher -- Teinturier, Samuel -- ten Kate, Inge -- Thomas, Peter -- Thompson, Lucy -- Tokar, Robert -- Toplis, Mike -- Torres Redondo, Josefina -- Trainer, Melissa -- Treiman, Allan -- Tretyakov, Vladislav -- Urqui-O'Callaghan, Roser -- Van Beek, Jason -- Van Beek, Tessa -- VanBommel, Scott -- Vaniman, David -- Varenikov, Alexey -- Vasavada, Ashwin -- Vasconcelos, Paulo -- Vicenzi, Edward -- Vostrukhin, Andrey -- Voytek, Mary -- Wadhwa, Meenakshi -- Ward, Jennifer -- Weigle, Eddie -- Wellington, Danika -- Westall, Frances -- Wiens, Roger Craig -- Wilhelm, Mary Beth -- Williams, Amy -- Williams, Joshua -- Williams, Rebecca -- Williams, Richard B -- Wilson, Mike -- Wimmer-Schweingruber, Robert -- Wolff, Mike -- Wong, Mike -- Wray, James -- Wu, Megan -- Yana, Charles -- Yen, Albert -- Yingst, Aileen -- Zeitlin, Cary -- Zimdar, Robert -- Zorzano Mier, Maria-Paz -- New York, N.Y. -- Science. 2013 Jul 19;341(6143):260-3. doi: 10.1126/science.1237961.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA. chris.r.webster@jpl.nasa.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23869013" target="_blank"〉PubMed〈/a〉

Description: The ChemCam instrument, which provides insight into martian soil chemistry at the submillimeter scale, identified two principal soil types along the Curiosity rover traverse: a fine-grained mafic type and a locally derived, coarse-grained felsic type. The mafic soil component is representative of widespread martian soils and is similar in composition to the martian dust. It possesses a ubiquitous hydrogen signature in ChemCam spectra, corresponding to the hydration of the amorphous phases found in the soil by the CheMin instrument. This hydration likely accounts for an important fraction of the global hydration of the surface seen by previous orbital measurements. ChemCam analyses did not reveal any significant exchange of water vapor between the regolith and the atmosphere. These observations provide constraints on the nature of the amorphous phases and their hydration.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Meslin, P-Y -- Gasnault, O -- Forni, O -- Schroder, S -- Cousin, A -- Berger, G -- Clegg, S M -- Lasue, J -- Maurice, S -- Sautter, V -- Le Mouelic, S -- Wiens, R C -- Fabre, C -- Goetz, W -- Bish, D -- Mangold, N -- Ehlmann, B -- Lanza, N -- Harri, A-M -- Anderson, R -- Rampe, E -- McConnochie, T H -- Pinet, P -- Blaney, D -- Leveille, R -- Archer, D -- Barraclough, B -- Bender, S -- Blake, D -- Blank, J G -- Bridges, N -- Clark, B C -- DeFlores, L -- Delapp, D -- Dromart, G -- Dyar, M D -- Fisk, M -- Gondet, B -- Grotzinger, J -- Herkenhoff, K -- Johnson, J -- Lacour, J-L -- Langevin, Y -- Leshin, L -- Lewin, E -- Madsen, M B -- Melikechi, N -- Mezzacappa, A -- Mischna, M A -- Moores, J E -- Newsom, H -- Ollila, A -- Perez, R -- Renno, N -- Sirven, J-B -- Tokar, R -- de la Torre, M -- d'Uston, L -- Vaniman, D -- Yingst, A -- MSL Science Team -- New York, N.Y. -- Science. 2013 Sep 27;341(6153):1238670. doi: 10.1126/science.1238670.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Universite de Toulouse, UPS-OMP, IRAP, 31028 Toulouse, France. pmeslin@irap.omp.eu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24072924" target="_blank"〉PubMed〈/a〉

Description: The Rocknest aeolian deposit is similar to aeolian features analyzed by the Mars Exploration Rovers (MERs) Spirit and Opportunity. The fraction of sand 〈150 micrometers in size contains ~55% crystalline material consistent with a basaltic heritage and ~45% x-ray amorphous material. The amorphous component of Rocknest is iron-rich and silicon-poor and is the host of the volatiles (water, oxygen, sulfur dioxide, carbon dioxide, and chlorine) detected by the Sample Analysis at Mars instrument and of the fine-grained nanophase oxide component first described from basaltic soils analyzed by MERs. The similarity between soils and aeolian materials analyzed at Gusev Crater, Meridiani Planum, and Gale Crater implies locally sourced, globally similar basaltic materials or globally and regionally sourced basaltic components deposited locally at all three locations.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Blake, D F -- Morris, R V -- Kocurek, G -- Morrison, S M -- Downs, R T -- Bish, D -- Ming, D W -- Edgett, K S -- Rubin, D -- Goetz, W -- Madsen, M B -- Sullivan, R -- Gellert, R -- Campbell, I -- Treiman, A H -- McLennan, S M -- Yen, A S -- Grotzinger, J -- Vaniman, D T -- Chipera, S J -- Achilles, C N -- Rampe, E B -- Sumner, D -- Meslin, P-Y -- Maurice, S -- Forni, O -- Gasnault, O -- Fisk, M -- Schmidt, M -- Mahaffy, P -- Leshin, L A -- Glavin, D -- Steele, A -- Freissinet, C -- Navarro-Gonzalez, R -- Yingst, R A -- Kah, L C -- Bridges, N -- Lewis, K W -- Bristow, T F -- Farmer, J D -- Crisp, J A -- Stolper, E M -- Des Marais, D J -- Sarrazin, P -- MSL Science Team -- New York, N.Y. -- Science. 2013 Sep 27;341(6153):1239505. doi: 10.1126/science.1239505.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉National Aeronautics and Space Administration Ames Research Center, Moffett Field, CA 94035, USA. david.blake@nasa.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24072928" target="_blank"〉PubMed〈/a〉

Description: Hydrated evaporite minerals have the ability to hold large amounts of H 2 O, making them a potential source of H 2 O in cold, low- P H 2 O environments such as the surface of Mars. Many of these hydrated evaporite minerals experience a reversible change in hydration state in response to changes in temperature ( T ) and relative humidity (RH). Such phases may thus have the potential to interact with the martian atmosphere on a daily or seasonal basis. The Na 2 Mg(SO 4 ) 2 · n H 2 O system was previously thought to contain three hydrated phases: a decahydrate ( n = 10), konyaite ( n = 5), and blödite ( n = 4). We examined this system using temperature- and RH-controlled X-ray powder diffraction (XRD) methods, as well as temperature-controlled single-crystal X-ray diffraction. When blödite was exposed to sub-freezing conditions, T ≤ –10 °C, a new phase was produced ( n = 16, 52 wt%H 2 O). Similar low-temperature behavior has been documented in the MgSO 4 · n H 2 O system, through the presence of meridianiite ( Peterson et al. 2007 ). The hydration and dehydration behavior of phases in the Na 2 Mg(SO 4 ) 2 · n H 2 O system was evaluated with powder XRD from –30 to 〉25 °C and from ~99 to near 0% RH, and single-crystal XRD data were collected for the n = 16 phase at –120 °C. The 16-hydrate is triclinic, space group P , with unit-cell parameters a = 6.5590(12), b = 6.6277(14), c = 14.441(3) Å, α = 87.456(15)°, β = 79.682(15)°, = 65.847(13)°, and a unit-cell volume of 563.3(2) Å 3 . The existence of this new phase at low temperatures, its high hydration state, and its ability to form reversibly from blödite all suggest that if phases in this system exist on the martian surface, they will participate in the Mars H 2 O cycle.

Description: The distribution of porosity was examined on seven drill cores from west–central Alberta encompassing the Belle Fourche and Second White Specks Formations. These Cenomanian–Turonian mudrocks from the Western Canada Sedimentary Basin exhibit good organic richness (〉2 wt. % total organic carbon) and marine kerogen type II with limited kerogen type III. With the increasing thermal maturity from approximately 0.43% vitrinite reflectance ( R o ) to approximately 0.90% R o , the total porosity decreases from approximately 9 to approximately 1 vol. %. This change translates to a reduction in total pore volume from approximately 0.05 to approximately 0.005 cm 3 /g and is accompanied by changes in relative proportions of micropore, mesopore, and macropore volumes. Variations in total porosity for the seven cores with different thermal maturities across Alberta are mainly related to mesoporosity and macroporosity, although the in-core variations in total porosity are mainly related to microporosity. In general, organic matter micropores contribute to the overall microporosity in the seven cores across the study area. The increase in the total pore volumes is in accordance with an increasing concentration of quartz, although increasing concentrations of chlorite and kaolinite may contribute to greater abundance of micropores in the seven cores. The in-core variations suggest that greater contents of kaolinite and illite may contribute to increasing mesopore volumes. Variations in pore volumes and pore size distribution with depth within individual cores (representing specific thermal maturity level) differ from what is observed laterally, when cores of various thermal maturity levels across Alberta are compared, indicating complex controls on porosity systems.

Description: We present an X-ray diffraction and multi-nuclear ( 2 H and 43 Ca) NMR study of Ca-exchanged hectorite (a smectite clay) that provides important new insight into molecular behavior at the smectite-H 2 O interface. Variable-temperature 43 Ca MAS NMR and controlled humidity XRD indicate that Ca 2+ occurs as proximity-restricted outer-sphere hydration complexes between –120 and +25 °C in a two-layer hydrate and at T ≤ –50 °C in a 2:1 water/solid paste. Changes in the 43 Ca NMR peak width and position with temperature are more consistent with diffusion-related processes than with dynamics involving metal-surface interactions such as site exchange. The 2 H NMR signal between –50 and +25 °C for a two-layer hydrate of Ca-hectorite is similar to that of Na- and other alkali metal hectorites and represents 2 H 2 O molecules experiencing anisotropic motion describable using the 2 H C 2 /C 3 jump model we proposed previously. 2 H T 1 relaxation results for Ca- and Na-hectorite are well fit with a fast-exchange limit, rotational diffusion model for 2 H 2 O dynamics, yielding GHz-scale rotational reorientation rates compatible with the C 3 component of the C 2 /C 3 hopping model. The apparent activation energy for 2 H 2 O rotational diffusion in the two-layer hydrate is greater for Ca-hectorite than Na-hectorite (25.1 vs. 21.1 kJ/mol), consistent with the greater affinity of Ca 2+ for H 2 O. The results support the general principle that the dynamic mechanisms of proximity-restricted H 2 O are only weakly influenced by the cation in alkali metal and alkaline earth metal smectites and provide critical evidence that the NMR resonances of charge-balancing cations in smectites become increasingly influenced by diffusion-like dynamic processes at low temperatures as the charge density of the unhydrated cation increases.

Description: The Mars Science Laboratory (MSL) rover Curiosity has documented a section of fluvio-lacustrine strata at Yellowknife Bay (YKB), an embayment on the floor of Gale crater, approximately 500 m east of the Bradbury landing site. X-ray diffraction (XRD) data and evolved gas analysis (EGA) data from the CheMin and SAM instruments show that two powdered mudstone samples (named John Klein and Cumberland) drilled from the Sheepbed member of this succession contain up to ~20 wt% clay minerals. A trioctahedral smectite, likely a ferrian saponite, is the only clay mineral phase detected in these samples. Smectites of the two samples exhibit different 001 spacing under the low partial pressures of H 2 O inside the CheMin instrument (relative humidity 〈1%). Smectite interlayers in John Klein collapsed sometime between clay mineral formation and the time of analysis to a basal spacing of 10 Å, but largely remain open in the Cumberland sample with a basal spacing of ~13.2 Å. Partial intercalation of Cumberland smectites by metal-hydroxyl groups, a common process in certain pedogenic and lacustrine settings on Earth, is our favored explanation for these differences. The relatively low abundances of olivine and enriched levels of magnetite in the Sheepbed mudstone, when compared with regional basalt compositions derived from orbital data, suggest that clay minerals formed with magnetite in situ via aqueous alteration of olivine. Mass-balance calculations are permissive of such a reaction. Moreover, the Sheepbed mudstone mineral assemblage is consistent with minimal inputs of detrital clay minerals from the crater walls and rim. Early diagenetic fabrics suggest clay mineral formation prior to lithification. Thermodynamic modeling indicates that the production of authigenic magnetite and saponite at surficial temperatures requires a moderate supply of oxidants, allowing circum-neutral pH. The kinetics of olivine alteration suggest the presence of fluids for thousands to hundreds of thousands of years. Mineralogical evidence of the persistence of benign aqueous conditions at YKB for extended periods indicates a potentially habitable environment where life could establish itself. Mediated oxidation of Fe 2+ in olivine to Fe 3+ in magnetite, and perhaps in smectites provided a potential energy source for organisms.

Description: Ferrian saponite from the eastern Santa Monica Mountain, near Griffith Park (Los Angeles, California), was investigated as a mineralogical analog to smectites discovered on Mars by the CheMin X-ray diffraction instrument onboard the Mars Science Laboratory (MSL) rover. The martian clay minerals occur in sediment of basaltic composition and have 02 l diffraction bands peaking at 4.59 Å, consistent with tri-octahedral smectites. The Griffith saponite occurs in basalts as pseudomorphs after olivine and mesostasis glass and as fillings of vesicles and cracks and has 02 l diffraction bands at that same position. We obtained chemical compositions (by electron microprobe), X-ray diffraction patterns with a lab version of the CheMin instrument, Mössbauer spectra, and visible and near-IR reflectance (VNIR) spectra on several samples from that locality. The Griffith saponite is magnesian, Mg/(Mg+Fe) = 65–70%, lacks tetrahedral Fe 3+ and octahedral Al 3+ , and has Fe 3+ /Fe from 64 to 93%. Its chemical composition is consistent with a fully tri-octahedral smectite, but the abundance of Fe 3+ gives a nominal excess charge of +1 to +2 per formula unit. The excess charge is likely compensated by substitution of O 2– for OH – , causing distortion of octahedral sites as inferred from Mössbauer spectra. We hypothesize that the Griffith saponite was initially deposited with all its iron as Fe 2+ and was oxidized later. X-ray diffraction shows a sharp 001 peak at 15 Å, 00 l peaks, and a 02 l diffraction band at the same position (4.59 Å) and shape as those of the martian samples, indicating that the martian saponite is not fully oxidized. VNIR spectra of the Griffith saponite show distinct absorptions at 1.40, 1.90, 2.30–2.32, and 2.40 μm, arising from H 2 O and hydroxyl groups in various settings. The position of the ~2.31 μm spectral feature varies systematically with the redox state of the octahedrally coordinated Fe. This correlation may permit surface oxidation state to be inferred (in some cases) from VNIR spectra of Mars obtained from orbit, and, in any case, ferrian saponite is a viable assignment for spectral detections in the range 2.30–2.32 μm.