| 1. |
- Farley, K.A., et al.
(författare)
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In situ radiometric and exposure age dating of the martian surface
- 2014
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 343:6169
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Tidskriftsartikel (refereegranskat)abstract
- We determined radiogenic and cosmogenic noble gases in a mudstone on the floor of Gale Crater. A K-Ar age of 4.21 ± 0.35 billion years represents a mixture of detrital and authigenic components and confirms the expected antiquity of rocks comprising the crater rim. Cosmic-ray-produced 3He, 21Ne, and 36Ar yield concordant surface exposure ages of 78 ± 30 million years. Surface exposure occurred mainly in the present geomorphic setting rather than during primary erosion and transport. Our observations are consistent with mudstone deposition shortly after the Gale impact or possibly in a later event of rapid erosion and deposition. The mudstone remained buried until recent exposure by wind-driven scarp retreat. Sedimentary rocks exposed by this mechanism may thus offer the best potential for organic biomarker preservation against destruction by cosmic radiation.
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| 2. |
- Ming, D.W., et al.
(författare)
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Volatile and organic compositions of sedimentary rocks in Yellowknife Bay, Gale Crater, Mars
- 2014
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 343:6169
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Tidskriftsartikel (refereegranskat)abstract
- H2O, CO2, SO2, O2, H2, H2S, HCl, chlorinated hydrocarbons, NO, and other trace gases were evolved during pyrolysis of two mudstone samples acquired by the Curiosity rover at Yellowknife Bay within Gale crater, Mars. H2O/OH-bearing phases included 2:1 phyllosilicate(s), bassanite, akaganeite, and amorphous materials. Thermal decomposition of carbonates and combustion of organic materials are candidate sources for the CO2. Concurrent evolution of O2 and chlorinated hydrocarbons suggests the presence of oxychlorine phase(s). Sulfides are likely sources for sulfur-bearing species. Higher abundances of chlorinated hydrocarbons in the mudstone compared with Rocknest windblown materials previously analyzed by Curiosity suggest that indigenous martian or meteoritic organic carbon sources may be preserved in the mudstone; however, the carbon source for the chlorinated hydrocarbons is not definitively of martian origin.
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| 3. |
- Vaniman, D.T., et al.
(författare)
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Mineralogy of a mudstone at Yellowknife Bay, Gale Crater, Mars
- 2014
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 343:6169
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Tidskriftsartikel (refereegranskat)abstract
- Sedimentary rocks at Yellowknife Bay (Gale crater) on Mars include mudstone sampled by the Curiosity rover. The samples, John Klein and Cumberland, contain detrital basaltic minerals, calcium sulfates, iron oxide or hydroxides, iron sulfides, amorphous material, and trioctahedral smectites. The John Klein smectite has basal spacing of ~10 angstroms, indicating little interlayer hydration. The Cumberland smectite has basal spacing at both ~13.2 and ~10 angstroms. The larger spacing suggests a partially chloritized interlayer or interlayer magnesium or calcium facilitating H2O retention. Basaltic minerals in the mudstone are similar to those in nearby eolian deposits. However, the mudstone has far less Fe-forsterite, possibly lost with formation of smectite plus magnetite. Late Noachian/Early Hesperian or younger age indicates that clay mineral formation on Mars extended beyond Noachian time.
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| 4. |
- Wang, Xiaofeng, et al.
(författare)
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Evidence for type ia supernova diversity from ultraviolet observations with the hubble space telescope
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 749:2, s. 126-
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Tidskriftsartikel (refereegranskat)abstract
- We present ultraviolet (UV) spectroscopy and photometry of four Type Ia supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) obtained with the UV prism of the Advanced Camera for Surveys on the Hubble Space Telescope. This data set provides unique spectral time series down to 2000 angstrom. Significant diversity is seen in the near-maximum-light spectra (similar to 2000-3500 angstrom) for this small sample. The corresponding photometric data, together with archival data from Swift Ultraviolet/Optical Telescope observations, provide further evidence of increased dispersion in the UV emission with respect to the optical. The peak luminositiesmeasured in the uvw1/F250W filter are found to correlate with the B-band light-curve shape parameter Delta m(15)(B), but with much larger scatter relative to the correlation in the broadband B band (e.g., similar to 0.4 mag versus similar to 0.2 mag for those with 0.8 mag < Delta m(15)(B) < 1.7 mag). SN 2004dt is found as an outlier of this correlation (at > 3 sigma), being brighter than normal SNe Ia such as SN 2005cf by similar to 0.9 mag and similar to 2.0 mag in the uvw1/F250W and uvm2/F220W filters, respectively. We show that different progenitor metallicity or line-expansion velocities alone cannot explain such a large discrepancy. Viewing-angle effects, such as due to an asymmetric explosion, may have a significant influence on the flux emitted in the UV region. Detailed modeling is needed to disentangle and quantify the above effects.
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| 5. |
- Cruchley, S., et al.
(författare)
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Cautionary note on use of focused ion beam sectioning as technique for characterising oxidation damage in Ni based superalloys
- 2014
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Ingår i: Materials at High Temperature. - : Science Reviews 2000 Ltd.. - 0960-3409 .- 1878-6413. ; 31:1, s. 27-33
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Tidskriftsartikel (refereegranskat)abstract
- Previous observations on Ni based superalloys, obtained through the use of focused ion beam (FIB) sample preparation and imaging, have reported the presence of subsurface voids after oxidation. In this present study, oxidised specimens of the Ni based superalloy, RR1000, were subjected to conventional sample preparation as well as both dual and single beam FIB preparation, with the aim of re-examining the previous observations of subsurface void formation. It is clear from FIB preparations that features previously interpreted as networks of voids have been demonstrated to be internal oxides by varying the sample tilt angles and imaging signal using either secondary electrons (SEs) or secondary ions (SIs). Conventional preparation methods illustrate the presence of subsurface alumina intrusions and the absence of voids, supporting previous evidence. The positive identification of voids and oxides by FIB can be complex and prone to misinterpretation and thus, the use of several imaging conditions and tilt angles must be used, along with conventional preparation methods, to confirm or refute the presence of voids underneath oxides.
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| 6. |
- Grotzinger, J.P., et al.
(författare)
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A habitable fluvio-lacustrine environment at Yellowknife Bay, Gale Crater, Mars
- 2014
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 343:6169
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Tidskriftsartikel (refereegranskat)abstract
- The Curiosity rover discovered fine-grained sedimentary rocks, which are inferred to represent an ancient lake and preserve evidence of an environment that would have been suited to support a martian biosphere founded on chemolithoautotrophy. This aqueous environment was characterized by neutral pH, low salinity, and variable redox states of both iron and sulfur species. Carbon, hydrogen, oxygen, sulfur, nitrogen, and phosphorus were measured directly as key biogenic elements; by inference, phosphorus is assumed to have been available. The environment probably had a minimum duration of hundreds to tens of thousands of years. These results highlight the biological viability of fluvial-lacustrine environments in the post-Noachian history of Mars.
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| 7. |
- Leshin, L.A., et al.
(författare)
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Volatile, Isotope, and Organic Analysis of Martian Fines with the Mars Curiosity Rover
- 2013
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 341:6153
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Tidskriftsartikel (refereegranskat)abstract
- Samples from the Rocknest aeolian deposit were heated to ~835°C under helium flow and evolved gases analyzed by Curiosity’s Sample Analysis at Mars instrument suite. H2O, SO2, CO2, and O2 were the major gases released. Water abundance (1.5 to 3 weight percent) and release temperature suggest that H2O is bound within an amorphous component of the sample. Decomposition of fine-grained Fe or Mg carbonate is the likely source of much of the evolved CO2. Evolved O2 is coincident with the release of Cl, suggesting that oxygen is produced from thermal decomposition of an oxychloride compound. Elevated δD values are consistent with recent atmospheric exchange. Carbon isotopes indicate multiple carbon sources in the fines. Several simple organic compounds were detected, but they are not definitively martian in origin.
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| 8. |
- Paolucci, M., et al.
(författare)
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Towards a living earth simulator
- 2012
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Ingår i: The European Physical Journal Special Topics. - : Springer Science and Business Media LLC. - 1951-6355 .- 1951-6401. ; 214:1, s. 77-108
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Tidskriftsartikel (refereegranskat)abstract
- The Living Earth Simulator (LES) is one of the core componentsof the FuturICT architecture. It will work as a federation ofmethods, tools, techniques and facilities supporting all of the FuturICTsimulation-related activities to allow and encourage interactive explorationand understanding of societal issues. Society-relevant problemswill be targeted by leaning on approaches based on complex systemstheories and data science in tight interaction with the other componentsof FuturICT. The LES will evaluate and provide answers to realworldquestions by taking into account multiple scenarios. It will buildon present approaches such as agent-based simulation and modeling,multiscale modelling, statistical inference, and data mining, movingbeyond disciplinary borders to achieve a new perspective on complexsocial systems.
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