Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars

The Sample Analysis at Mars (SAM) instrument on board the Mars Science Laboratory 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. 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. Here we report the definitive identification of chlorobenzene (150–300 parts per billion by weight (ppbw)) and C_2 to C_4 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

Quantitative Paleobathymetry of Early Proterozoic (1.9 B.Y.) Continental Slope, Rocknest Formation, Wopmay Orogen, N.W.T., Canada

The Rocknest Formation is an early Proterozoic (1.9 b.y.) westward-facing, rimmed carbonate shelf that evolved from a ramp developed on quartzites of the underlying Odjick Formation. Shelf interior facies are cyclic peritidal dolomites; shelf edge facies are reefal stromatolitic boundstones and intraclast/ooid grainstones, and slope facies are turbidites, slope breccias, and shelf edge breccias. The carbonates are overlain by black shales and graywackes of the Recluse Group

Aspects of the Rocknest Formation, Asiak Thrust-fold Belt, Wopmay Orogen, District of Mackenzie

Field study of the Rocknest Formation during 1981 and 1982, and laboratory study during the fall of 1982 has produced several interesting findings which are summarized in this report. Topics are: 1) subdivision of Rocknest Formation into ten informal members, 2) Rocknest shelf cyclicity and paleogeography, 3) shelf-to- slope transitions, 4) paleoclimate, and 5) evidence of possible microbial remnants in stromatolite bioherms of the Odjick/Rocknest transition beds. Future fieldwork is outlined

Preliminary Investigations of Early Proterozoic western River and Burnside River Formations : Evidence For Foredeep Origin of Kilohigok Basin, District of Mackenzie

In the Kilohigok Basin, the Western River and Burnside River formations comprise three successively overlying tectono-stratigraphic sedimentary units of regional extent: a basal shallow water siliciclastic/carbonate platform, overlain by deepwater flysch, in turn overlain by shallow marine and fluvial molasse. This stratigraphy represents an initial stable shelf (passive margin?) whose outer, southerly edge rapidly subsided contemporaneous with arching and subaerial exposure of its interior. Shelf drowning represents the onset of foredeep subsidence subparallel to the trend of Thelon Tectonic Zone. Arching and subsidence were perpendicular to the tectonic transport direction of intrabasinal nappes. indicating that convergence and uplift a long Thelon Tectonic Zone were probably responsible for foredeep subsidence within Ki lohigok Basin. Following drowning, the platform was buried by deepwater deposits ( flysch); with progressive uplift and basin filling, the foredeep entered the molasse phase and fluvial sediments prograded towards the foreland. The foredeep model places constraints on the origin of Thelon Tectonic Zone and provides a more comprehensive understanding of the tectonic evolution of the Slave Province and its relation to the Wopmay Orogen

Physicochemical properties of concentrated Martian surface waters

Understanding the processes controlling chemical sedimentation is an important step in deciphering paleoclimatic conditions from the rock records preserved on both Earth and Mars. Clear evidence for subaqueous sedimentation at Meridiani Planum, widespread saline mineral deposits in the Valles Marineris region, and the possible role of saline waters in forming recent geomorphologic features all underscore the need to understand the physical properties of highly concentrated solutions on Mars in addition to, and as a function of, their distinct chemistry. Using thermodynamic models predicting saline mineral solubility, we generate likely brine compositions ranging from bicarbonate-dominated to sulfate-dominated and predict their saline mineralogy. For each brine composition, we then estimate a number of thermal, transport, and colligative properties using established models that have been developed for highly concentrated multicomponent electrolyte solutions. The available experimental data and theoretical models that allow estimation of these physicochemical properties encompass, for the most part, much of the anticipated variation in chemistry for likely Martian brines. These estimates allow significant progress in building a detailed analysis of physical sedimentation at the ancient Martian surface and allow more accurate predictions of thermal behavior and the diffusive transport of matter through chemically distinct solutions under comparatively nonstandard conditions

Opportunity Mars Rover mission: Overview and selected results from Purgatory ripple to traverses to Endeavour crater

Opportunity has been traversing the Meridiani plains since 25 January 2004 (sol 1), acquiring numerous observations of the atmosphere, soils, and rocks. This paper provides an overview of key discoveries between sols 511 and 2300, complementing earlier papers covering results from the initial phases of the mission. Key new results include (1) atmospheric argon measurements that demonstrate the importance of atmospheric transport to and from the winter carbon dioxide polar ice caps; (2) observations showing that aeolian ripples covering the plains were generated by easterly winds during an epoch with enhanced Hadley cell circulation; (3) the discovery and characterization of cobbles and boulders that include iron and stony-iron meteorites and Martian impact ejecta; (4) measurements of wall rock strata within Erebus and Victoria craters that provide compelling evidence of formation by aeolian sand deposition, with local reworking within ephemeral lakes; (5) determination that the stratigraphy exposed in the walls of Victoria and Endurance craters show an enrichment of chlorine and depletion of magnesium and sulfur with increasing depth. This result implies that regional-scale aqueous alteration took place before formation of these craters. Most recently, Opportunity has been traversing toward the ancient Endeavour crater. Orbital data show that clay minerals are exposed on its rim. Hydrated sulfate minerals are exposed in plains rocks adjacent to the rim, unlike the surfaces of plains outcrops observed thus far by Opportunity. With continued mechanical health, Opportunity will reach terrains on and around Endeavour's rim that will be markedly different from anything examined to date

The externides of Wopmay Orogen, Point Lake and Kikerk Lake map areas, District of Mackenzie

Some results of recent field work are briefly discussed as they pertain to the following topics: (1) north-south stratigraphic continuity of the Precambrian continental-terrace wedge, (2) stromatolite elongation, paleowind direction and global polarity during deposition of the Rocknest dolomite shelf, (3) evidence for primary aragonitic mineralogy of the Rocknest Formation, (4) attempted quantitative paleobathymetry of the upper continental slope, (5) eastward migration of foredeep flysch, (6) nature of basement involvement in Asiak Fold-Thrust Belt, (7) relation of thrusting to the foredeep molasse, (8) mysterious basement-involved cross folding of regional extent, (9) normal faults associated with late transcurrent faulting , and (10) the first reported minor leadzinc vein mineralization in Rocknest dolomite. Future field work is outlined

Controls on development and diversity of Early Archean stromatolites

The ≈3,450-million-year-old Strelley Pool Formation in Western Australia contains a reef-like assembly of laminated sedimentary accretion structures (stromatolites) that have macroscale characteristics suggestive of biological influence. However, direct microscale evidence of biology—namely, organic microbial remains or biosedimentary fabrics—has to date eluded discovery in the extensively-recrystallized rocks. Recently-identified outcrops with relatively good textural preservation record microscale evidence of primary sedimentary processes, including some that indicate probable microbial mat formation. Furthermore, we find relict fabrics and organic layers that covary with stromatolite morphology, linking morphologic diversity to changes in sedimentation, seafloor mineral precipitation, and inferred microbial mat development. Thus, the most direct and compelling signatures of life in the Strelley Pool Formation are those observed at the microscopic scale. By examining spatiotemporal changes in microscale characteristics it is possible not only to recognize the presence of probable microbial mats during stromatolite development, but also to infer aspects of the biological inputs to stromatolite morphogenesis. The persistence of an inferred biological signal through changing environmental circumstances and stromatolite types indicates that benthic microbial populations adapted to shifting environmental conditions in early oceans

Singularity analysis: a tool for extracting lithologic and stratigraphic content from seismic data

In this work, we test an amplitude-independent method of seisimic data analysis designed to extract lithologic information about stratigraphic horizons. We apply the method of singularity characterization in an attempt to determine the sharpness of lithologic boundaries. We infer the sharpness of the boundary based upon a fractional integration of the seismic trace. The order of fractional integration is taken to represent the abruptness of the lithologic transition responsible for a given reflector. We find that the method output behaves in a geologically reasonable manner which suggests that our method is responding to lithologic variations along boundaries responsible for prominent reflectors in the data