¹Gwenaël Hervé,¹Stuart A. Gilder,²Cassandra L. Marion,^2,3Gordon R. Osinski,¹Jean Pohl,¹Nikolai Petersen,⁴Paul J. Sylvester
¹Department of Earth and Environmental Sciences, Ludwig Maximilians Universität, Munich, Germany
²Department of Earth Sciences & Centre for Planetary Science and Exploration, University of Western Ontario, Canada
³Department of Physics and Astronomy, University of Western Ontario, Canada
⁴Department of Geosciences, Texas Tech University, 125 Science Building, Lubbock, TX 79409-1053, USA

We carried out an integrated rock magnetic and paleomagnetic study of the ∼36 Ma Mistastin Lake (Labrador, Canada) meteorite impact structure in order to investigate whether energy from the collision influenced the geodynamo and to assess the effects of shock on the magnetic properties of the target basement rocks. Stepwise demagnetization of 114 specimens isolates a well-defined magnetization component throughout the crater whose overall mean deviates slightly from the expected direction for North America at the time of impact. Paleointensity results from seven samples meeting stringent selection criteria show no significant difference with a global compilation from 40 to 30 Ma. The combined results, including those from a ∼80 m-thick profile of an impact melt unit (Discovery Hill), lend no support that the impact caused an aberration of the geodynamo within a few centuries of a bolide collision that created the ∼28 km-diameter crater. Both titanium-rich and titanium-poor titanomagnetite carry the magnetic remanence in the impact melt rocks; their relative proportions, compositions and domain states are cooling rate dependent. Magnetic hysteresis parameters of the magnetite-bearing anorthositic basement rocks reveal systematic changes as a function of distance from the crater’s center with an increasing prevalence of single domain-like grains toward the center. Changes with radial distance are also found in the character of the Verwey transition in magnetite. Basement rocks were thermally overprinted when lying less than a meter from the impact melt rocks; Mesoproterozoic basement rocks more than a meter below the impact melt rocks hold similar magnetization directions to those expected from a 1500 Ma result for Laurentia. No evidence exists that shock heating of the basement rocks exceeded 200 °C at distances of 6–7 km from the crater’s center.

Reference
Hervé G, Gilder SA, Marion CL, Osinski GR, Pohl J, Petersen N, Sylvester PJ (2015) Paleomagnetic and rock magnetic study of the Mistastin Lake impact structure (Labrador, Canada): Implications for geomagnetic perturbation and shock effects. Earth and Planetary Science Letters (in Press)
Link to Article [doi:10.1016/j.epsl.2015.02.011]

Copyright Elsevier

¹Emily Dixon,¹Andrew Elwood Madden,²Elisabeth M. Hausrath,¹Megan Elwood Madden
¹School of Geology and Geophysics, University of Oklahoma, Norman, OK, USA
²Department of Geoscience, University of Nevada Las Vegas, Las Vegas, NV, USA

Jarosite flow-through dissolution experiments were conducted in ultrapure water (UPW), pH 2 sulfuric acid, and saturated NaCl and CaCl2 brines at 295-298 K to investigate how hydrologic variables may affect jarosite preservation and reaction products on Mars. K+ based dissolution rates in flowing UPW did not vary significantly with flow rate, indicating that mineral surface reactions control dissolution rates over the range of flow rates investigated. In all of the solutions tested, hydrologic variables do not significantly affect extent of jarosite alteration; therefore jarosite is equally likely to be preserved in flowing or stagnant waters on Mars. However, increasing flow rate did affect the mineralogy and accumulation of secondary reaction products. Iron release rates in dilute solutions increased as the flow rate increased, likely due to nanoscale iron (hydr)oxide transport in flowing water. Anhydrite formed in CaCl2 brine flow-through experiments despite low temperatures, while metastable gypsum and bassanite were observed in batch experiments. Therefore, observations of the hydration state of calcium sulfate minerals on Mars may provide clues to unravel past salinity and hydrologic conditions as well as temperatures and vapor pressures.

Reference
Dixon E, Madden AE, Hausrath EM, Madden ME (2015) Assessing hydrodynamic effects on jarosite dissolution rates, reaction products, and preservation on Mars. Journal of Geophysical Research Planets (in Press)
Link to Article [DOI: 10.1002/2014JE004779]

Published by arrangement with John Wiley&Sons

¹Timothy A. Goudge,¹John F. Mustard,¹James W. Head,²Caleb I. Fassett,¹Sandra M. Wiseman
¹DepDepartment of Astronomy, Mount Holyoke College, South Hadley, MA, USA
²Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI, USA

We present results from geomorphic mapping and visible to near-infrared spectral analyses of the Jezero crater paleolake basin and its associated watershed. The goal of this study is to understand the provenance of the sedimentary deposits within this open-basin lake using a source-to-sink approach. Two fan deposits located within the basin have distinct visible to near-infrared mineralogic signatures measured by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). The northern fan is spectrally characterized by a mixture of Mg-rich carbonate and olivine, while the western fan is characterized by Fe/Mg-smectite (e.g., saponite or nontronite) with variable amounts of Mg-rich carbonate and olivine in isolated exposures. The watersheds of these deposits contain a variety of geomorphic units that are likely to have supplied sediment to the Jezero crater paleolake, as the fluvial valleys that fed the basin incise these units. The geomorphic units include exposures of Fe/Mg-smectite-, olivine-, and Mg-rich carbonate-bearing terrain. We show that the difference in fan deposit mineralogy is a function of the areal exposure of the major geomorphic units within their watersheds. This indicates that the spectrally dominant aqueous alteration minerals in the fan deposits are primarily detrital, or transported, in nature and did not form in situ. We conclude that the aqueous alteration of the units in the watershed occurred prior to the fluvial activity that carved the valleys of the Jezero crater paleolake system, and that the two periods of aqueous activity are not genetically related.

Reference
Goudge TA, Mustard JF, Head JW, Fassett CI, Wiseman SM (2015) Assessing the Mineralogy of the Watershed and Fan Deposits of the Jezero Crater Paleolake System, Mars. Journal of Geophysical Research Planets (in Press)
Link to Article [DOI: 10.1002/2014JE004782]

Published by arrangement with John Wiley&Sons

^1,2C. Freissinet et al. (>10)*
¹Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA
²NASA Postdoctoral Program, (NPP), Oak Ridge Associated Universities, Oak Ridge, Tennessee, USA
*Find the extensive, full author and affiliation list on the publishers website

The Sample Analysis at Mars (SAM) instrument [Mahaffy et al., 2012] onboard the Mars Science Laboratory (MSL) Curiosity rover is designed to conduct inorganic and organic chemical analyses of the atmosphere and the surface regolith and rocks to help evaluate the past and present habitability potential of Mars at Gale Crater [Grotzinger et al., 2012]. Central to this task is the development of an inventory of any organic molecules present to elucidate processes associated with their origin, diagenesis, concentration and long-term preservation. This will guide the future search for biosignatures [Summons et al., 2011]. Here we report the definitive identification of chlorobenzene (150–300 parts per billion by weight (ppbw)) and C2 to C4 dichloroalkanes (up to 70 ppbw) with the SAM gas chromatograph mass spectrometer (GCMS), and detection of chlorobenzene in the direct evolved gas analysis (EGA) mode, in multiple portions of the fines from the Cumberland drill hole in the Sheepbed mudstone at Yellowknife Bay. When combined with GCMS and EGA data from multiple scooped and drilled samples, blank runs and supporting laboratory analog studies, the elevated levels of chlorobenzene and the dichloroalkanes cannot be solely explained by instrument background sources known to be present in SAM. We conclude that these chlorinated hydrocarbons are the reaction products of martian chlorine and organic carbon derived from martian sources (e.g. igneous, hydrothermal, atmospheric, or biological) or exogenous sources such as meteorites, comets or interplanetary dust particles.

Reference
Freissinet C et al. (2015) Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars. Journal of Geophysical Research, Planets (in Press)
Link to Article [DOI: 10.1002/2014JE004737]

Published by arrangement with John Wiley&Sons

¹Abu Asaduzzaman,¹Krishna Muralidharan,²Jibamitra Ganguly
¹Materials Science and Engineering, University of Arizona, Tucson, Arizona, USA
²Department of Geoscience, University of Arizona, Tucson, 85721, USA

Using density functional theory, we have examined the hydration mechanism of olivine with the objective of understanding the reaction pathways toward the formation of crystalline serpentine and brucite. It is found that further supply of water beyond saturation of the adsorption sites on olivine surfaces leads to the formation of amorphous brucite and serpentine molecules, with the latter forming in the subsurface domain. The calculated activation energy for this process is ~25 kJ mol−1, which permits formation of the amorphous materials well within the life span of the solar nebula. In addition, molecular dynamic simulations show that the adsorbed water in olivine is stable at least up to 900 K—a finding that is in accord with independent experimental studies. Thus, adsorption plus subsurface reaction of H2O in olivine could have taken place at temperatures considerably higher than the stability limit of hydrous minerals in the nebular condition. Using the DFT derived enthalpy of adsorption data, and reasonable approximation for the entropy of adsorption, we have calculated the fractional coverage of the reactive surface sites of olivine grains of spherical geometry by adsorbed water, and the corresponding ocean equivalent water (OEW) that could have been accreted into the Earth. These results suggest that adsorption and the associated subsurface hydroxylation of olivine grains might have been responsible for a significant fraction of the Earth’s water budget. The adsorption of water into olivine crystals in the solar nebula might also have led to the delivery of water to other planetary bodies.

Reference
Asaduzzaman A, Muralidharan K, Ganguly J (2015) Incorporation of water into olivine during nebular condensation: Insights from density functional theory and thermodynamics, and implications for phyllosilicate formation and terrestrial water inventory. Meteoritics&Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12409]

Copyright Elsevier

¹A. Kereszturi,²Sz. Ormandi,²S. Jozsa
¹Research Center for Astronomy and Earth Sciences, Konkoly Astronomical Institute, H-1121 Budapest, Konkoly Thege Miklos utca 15-17
²Eotvos Lorand University of Sciences, Faculty of Science, Department of Petrology and Geochemistry, Hungarian Academy of Sciences, 1117 Budapest, Pázmány Péter sétány 1/A

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Reference
Kereszturi A, Ormandi Sz, Jozsa S (2015) Processing in a transitional environment of CV and CK chondrites’ parent bodies in the light of mineralogical and petrological analysis of NWA 1465 CV3 Meteorite. Planetary and Space Science (in Press)
Link to Article [doi:10.1016/j.pss.2015.02.016]

¹Wei, J., ¹Wang, A., ²Lambert, J.L., ³Wettergreen, D., ⁴Cabrol, N., ⁴Warren-Rhodes, K., ⁵Zacny, K.
¹Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences Washington University in St. Louis 1 Brookings Drive, St. Louis MO 63130 USA
²Jet Propulsion Laboratory 4800 Oak Grove Drive CA 91109 USA
³The Robotics Institute Carnegie Mellon University 5000 Forbes Avenue Pittsburgh PA 15213 USA
⁴The SETI Institute, Carl Sagan Center NASA Ames Research Center Moffett Field, CA 94035 USA
⁵HoneyBee Robotics and Spacecraft Mechanisms Corporation 398 West Washington Blvd, Suite 200 Pasadena, CA 91103 USA

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

Reference
Wei J, Wang A, Lambert JL, Wettergreen D, Cabrol N, Warren-Rhodes K, Zacny K (2015) Autonomous soil analysis by the Mars Micro-beam Raman Spectrometer (MMRS) on-board a rover in the Atacama Desert: a terrestrial test for planetary Exploration. Journal of Raman Spectroscopy (in Press)
Link to Article [DOI: 10.1002/jrs.4656]

¹John Carter, ²Christina Viviano-Beck, ³Damien Loizeau, ⁴Janice Bishop, ⁵Laetitia Le Deit
¹Institut d’Astrophysique Spatiale, Paris-Sud University, France
²Applied Physics Laboratory, John Hopkins University, Laurel, MD
³Laboratoire de Géologie de Lyon, Lyon 1 University, France
⁴SETI Institute, Mountatin View, CA
⁵Laboratoire de Planétologie et Géodynamique de Nantes, Nantes University, France

The Martian surface bears the mineralogical record of ancient sub-surface and surface aqueous alteration environments. While most of the chemical alteration produced phyllosilicates, hydrated sulfates and chlorides, other less common compounds provide key constraints on localized geochemical settings, and help refine the geological evolution of the planet. Using orbital imaging spectroscopy data, we report the detection of the iron chlorine hydroxide akaganéite (β-FeOOH,Cl) at several locations of Mars. Akaganéite is known to form in highly saline and chlorinated aqueous environments, and its occurrence in at least three basins of Mars suggests the existence of near-marine (lagoon-like) evaporitic settings early in Mars’ history. As a frequently biogenic mineral, the in-depth study of akaganéite and its relationship with other minerals will also provide an additional benchmark for the assessment of pre-biotic to biotic activity on Mars.

Reference
Carter J, Viviano-Beck C, Loizeau D, Bishop J, Le Deite L (2015) Orbital detection and implications of akaganéite on Mars. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.01.020]

Copyright Elsevier

¹Rebecca N. Greenberger,¹John F. Mustard,²Edward A. Cloutis,³Lisa M. Pratt,³Peter E. Sauer,²Paul Mann,⁴Kathryn Turner,⁵M. Darby Dyar,³David L. Bish
¹Department of Earth, Environmental, and Planetary Sciences, Brown University, 324 Brook St, Box 1846, Providence, RI 02912, USA
²Department of Geography, University of Winnipeg, 515 Portage Avenue, Winnipeg, Manitoba, R3B 2E9, Canada
³Department of Geological Sciences, Indiana University, 1001 East 10th Street, Bloomington, IN 47405-1405, USA
⁴Department of Physics, University of Winnipeg, 515 Portage Avenue, Winnipeg, Manitoba, R3B 2E9, Canada
⁵Mount Holyoke College, Department of Astronomy, 50 College St., South Hadley, MA 01075, USA

Molecular hydrogen produced through iron oxidation during formation of serpentine and magnetite can sustain terrestrial subsurface ecosystems. The Fe3+ in serpentine partitions into octahedral and tetrahedral sites differently as serpentinization proceeds, and tetrahedral Fe3+ is present toward the end of serpentinization. We map Fe oxidation states in a serpentinite to determine the degree to which serpentinization progressed and where hydrogen production has been maximized to assess habitability at an abandoned chrysotile mine in Norbestos, Quebec, in association with the Canadian Space Agency’s Mars Methane Analogue Mission. We also analyzed stable isotopes of carbon and oxygen in carbonates to constrain the conditions of water–rock interaction during serpentinization. Iron oxidation and coordination was determined through field imaging of rock walls with a visible hyperspectral imager (420–720 nm), and samples collected from imaged rocks and elsewhere in the mine were imaged in the laboratory (420–1100 nm). Sample chemistry, mineralogy, and oxidation state were determined with laboratory measurements of visible through mid-infrared reflectance spectra, major element chemistry, mineralogy, and Mössbauer spectroscopy. Mapping with hyperspectral imaging of outcrops and hand samples shows that tetrahedral Fe3+ is common in serpentinites at this site, and results are confirmed through other measurements. Major element chemistry and mineralogy are consistent with serpentine plus minor carbonate. Carbonate samples show an exceptional range in δ13C (−13.14 to +16.12‰+16.12‰ VPDB) and δ18O (−15.48 to −3.20‰−3.20‰ VPDB) that vary with location in the mine. Carbonates south of a shear zone (δ13C more positive) likely formed during periods of serpentinization in a carbon-limited reservoir closed to carbon addition but open to methane escape. Carbonates in a shear zone (δ13C more negative) probably formed later at low temperatures through CO2-metasomatism or atmospheric weathering, and isotopic trends are consistent with kinetic fractionation. The extensive presence of tetrahedral Fe3+ in serpentine shows the system liberally produced H2 while the isotope systematics have implications for preservation of indicators of the aqueous conditions that formed serpentinites on Mars and their habitability.

Reference
Greenberger RN, Mustard JF, Cloutis EA, Pratt LM, Sauer PE, Mann P, Turner K, Dyar MD, Bish DL (2015) Serpentinization, iron oxidation, and aqueous conditions in an ophiolite: Implications for hydrogen production and habitability on Mars. Earth and Planetary Science Letters 416, 21–34
Link to Article [doi:10.1016/j.epsl.2015.02.002]

Copyright Elsevier

The most popular papers in Cosmochemistry Papers in February were:

1-Young ED, Manning CE, Schauble EA, Shahar A, Macris CA, Lazar C, Jordan M (2015) High-temperature equilibrium isotope fractionation of non-traditional stable isotopes: Experiments, theory, and applications. Chemical Geology 395, 176-195 Link to Article [DOI: 10.1016/j.chemgeo.2014.12.013

2-Santos AR, Agee CB, McCubbin FM, Shearer CK, Burger PV, Tartèse R, Anand M (2015) Petrology of igneous clasts in Northwest Africa 7034: Implications for the petrologic diversity of the martian crust. Geochimica et Cosmochimica Acta (in Press) Link to Article [doi:10.1016/j.gca.2015.02.023]

3-Jacquet E, Alard O, Gounelle M (2015) Trace element geochemistry of ordinary chondrite chondrules: the type I/type II chondrule dichotomy. Geochimica et Cosmochimica Acta (in Press) Link to Article [doi:10.1016/j.gca.2015.02.005]

4-Luua T-H, Young ED, Gounelle M, Chaussidon M (2015) Short time interval for condensation of high-temperature silicates in the solar accretion disk. Proceedings of the National Academy of Sciences 112,5, 1298–1303 Link to Article [doi: 10.1073/pnas.1414025112]

5-Davis AM, Richter FM Mendybaev RA, Janney PE, Wadhwa M, McKeegan KD (2015) Isotopic mass fractionation laws for magnesium and their effects on 26Al-26Mg systematics in solar system materials. Geochimica et Cosmochimica Acta (in Press) Link to Article [doi:10.1016/j.gca.2015.01.034]