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101.
Previous orbital mapping of crystalline gray haematite, ferric oxides, and sulfates has shown an association of this mineralogy with light-toned, layered deposits on the floor of Valles Marineris, in chaos terrains in the canyon’s outflow channels, and in Meridiani Planum. The exact nature of the relationship between ferric oxides and sulfates within Valles Marineris is uncertain. The Observatoire pour la Mineralogie, l’Eau, les Glaces et l’Activite (OMEGA) spectrometer initially identified sulfate and ferric oxides in the layered deposits of Valles Marineris. The Thermal Emission Spectrometer (TES) has also mapped coarse (gray) haematite in or at the base of these deposits. We use Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) spectra and Context Camera (CTX) and High Resolution Imaging Science Experiment (HiRISE) imagery from the Mars Reconnaissance Orbiter (MRO) to explore the mineralogy and morphology of the large layered deposit in central Capri Chasma, part of the Valles Marineris canyon system that has large, clear exposures of sulfate and haematite. We find kieserite (MgSO4·H2O) and ferric oxide (often crystalline red haematite) in the lower bedrock exposures and a polyhydrated sulfate without ferric oxides in the upper bedrock. This stratigraphy is duplicated in many other basinal chasmata, suggesting a common genesis. We propose the haematite and monohydrated sulfate formed by diagenetic alteration of a sulfate-rich sedimentary deposit, where the upper polyhydrated sulfate-rich, haematite-poor layers either were not buried sufficiently to convert to a monohydrated sulfate or were part of a later depositional phase. Based on the similarities between the Valles Marineris assemblages and the sulfate and haematite-rich deposits of Meridiani Planum, we hypothesize a common evaporite and diagenetic formation process for the Meridiani Planum sediments and the sulfate-bearing basinal Interior Layered Deposits. 相似文献
102.
103.
Andrew J. Dombard Olivier S. Barnouin Louise M. Prockter Peter C. Thomas 《Icarus》2010,210(2):713-721
There are ∼300 features on the Asteroid 433 Eros that morphologically resemble ponds (flat-floored and sharply embaying the bounding depression in which they sit). Because boulders on Eros are apparently eroding in place and because ponds with associated boulders tend to be larger than ponds without blocks, we propose that ponds form from thermally disaggregated and seismically flattened boulder material, under the assumption that repeated day/night cycling causes material fatigue that leads to erosion of the boulders. Results from a simple boulder emplacement/thermal erosion model with boulders emplaced in a few discrete events (i.e., large impacts) match well the observed size distribution. Under this scenario, the subtle color differences of ponds (somewhat bluer than the rest of the surface) might be due to some combination of less space-weathered material and density stratification of silicate-rich chondrules and more metal-rich matrix from a disaggregated boulder. Volume estimates of ponds derived from NEAR Laser Rangefinder profiles are consistent with what can be supplied by boulders. Ponds are also observed to be concentrated in regions of low slope and high elevation, which suggests the presence of a less mobile regolith and thus a contrast in the resistance to seismic shaking between the pond material and the material that makes up the bounding depression. Future tests include shake-table experiments and temperature cycling (fatigue) of ordinary chondrites to test the thermal erosion mechanism. 相似文献
104.
Roberto Furfaro Jeffrey S. Kargel Wolfgang Fink Michael P. Bishop 《Planetary and Space Science》2010,58(5):761-779
Future planetary exploration of Titan will require higher degrees of on-board automation, including autonomous determination of sites where the probability of significant scientific findings is the highest. In this paper, a novel Artificial Intelligence (AI) method for the identification and interpretation of sites that yield the highest potential of cryovolcanic activity is presented. We introduce the theory of fuzzy cognitive maps (FCM) as a tool for the analysis of remotely collected data in planetary exploration. A cognitive model embedded in a fuzzy logic framework is constructed via the synergistic interaction of planetary scientists and AI experts. As an application example, we show how FCM can be employed to solve the challenging problem of recognizing cryovolcanism from Synthetic Aperture Radar (SAR) Cassini data. The fuzzy cognitive map is constructed using what is currently known about cryovolcanism on Titan and relies on geological mapping performed by planetary scientists to interpret different locales as cryovolcanic in nature. The system is not conceived to replace the human scientific interpretation, but to enhance the scientists’ ability to deal with large amounts of data, and it is a first step in designing AI systems that will be able, in the future, to autonomously make decisions in situations where human analysis and interpretation is not readily available or could not be sufficiently timely. The proposed FCM is tested on Cassini radar data to show the effectiveness of the system in reaching conclusions put forward by human experts and published in the literature. Four tests are performed using the Ta SAR image (October 2004 fly-by). Two regions (i.e. Ganesa Macula and the lobate high backscattering region East of Ganesa) are interpreted by the designed FCM as exhibiting cryovolcanism in agreement with the initial interpretation of the regions by Stofan et al. (2006). Importantly, the proposed FCM is shown to be flexible and adaptive as new data and knowledge are acquired during the course of exploration. Subsequently, the FCM has been modified to include topographic information derived from SAR stereo data. With this additional information, the map concludes that Ganesa Macula is not a cryovolcanic region. In conclusion, the FCM methodology is shown to be a critical and powerful component of future autonomous robotic spacecraft (e.g., orbiter(s), balloon(s), surface/lake lander(s), rover(s)) that will be deployed for the exploration of Titan. 相似文献
105.
Yuzong Zhang Jingxiu Wang Gemma D. R. Attrill Louise K. Harra Zhiliang Yang Xiangtao He 《Solar physics》2007,241(2):329-349
Coronal dimming can be considered to be a disk signature of front-side coronal mass ejections (CMEs) (Thompson et al.: 2000, Geophys. Res. Lett.
27, 1431). The study of the magnetic connectivity associated with coronal dimming can shed new light on the magnetic nature
of CMEs. In this study, four major flare-CME events on 14 July 2000, 28 October 2003, 7 November 2004, and 15 January 2005
are analyzed. They were all halo CMEs associated with major flare activity in complex active regions (ARs) and produced severe
space weather consequences. To explore the magnetic connectivity of these CMEs, global potential-field extrapolations based
on the composite synoptic magnetograms from the Michelson Doppler Imager onboard the Solar and Heliospheric Observatory are constructed, and their association with coronal dimming is revealed by the Extreme ultraviolet Imaging Telescope. It
is found that each flare-CME event involved interaction of more than ten sets of magnetic-loop systems. These loop systems
occupied over 50% of all identified loop systems in the visible hemisphere and covered a wide range of solar longitudes and
latitudes. We categorize the loop systems as active-region loops (ARLs), AR-interconnecting loops (ARILs) including transequatorial
loops (TLs), and long arcades (LAs) straddling filament channels. A recurring pattern, the saddle-field configuration (SFC),
consisting of ARILs, is found to be present in all four major flare-CME events. The magnetic connectivity revealed by this
work implies that intercoupling and interaction of multiple flux-loop systems are required for a major CME. For comparison,
a simple flare-CME event of 12 May 1997 with a relatively simple magnetic configuration is chosen. Even for this simple flare-CME
event, we find that multiple flux-loop systems are also present. 相似文献
106.
Arthur Clive Bishop Alan Robert Woolley 《Contributions to Mineralogy and Petrology》1973,39(4):309-326
The paper describes a suite of volcanic and intrusive rocks from Ua Pu, one of the Marquesas Islands, situated in the central Pacific Ocean. The rocks comprise alkali olivine basalts, hawaiites, mugearites, trachytes, and phonolites. Their petrographic characters are briefly described and 24 new chemical analyses presented. The rocks fall into a sodic and a potassic series, since some rocks are richer in K2O than Na2O, whilst the phonolites have exceptionally high total alkali contents.The differentiation of the series is discussed and special attention is paid to the phonolites in which icositetrahedral pseudomorphs occur. It is concluded that these pseudomorphs are probably after analcime rather than leucite. 相似文献
107.
108.
James A. Yoder Larry P. Atkinson S. Stephen Bishop Eileen E. Hofmann Thomas N. Lee 《Continental Shelf Research》1983,1(4):385-404
Gulf Stream frontal disturbances cause nutrient-rich waters to frequently upwell and intrude onto the southeastern United States continental shelf between Cape Canaveral, Florida and Cape Hatteras, North Carolina. Phytoplankton response in upwelled waters was determined with three interdisciplinary studies conducted during April 1979 and 1980, and in summer 1978. The results show that when shelf waters are not stratified, upwelling causes productive phytoplankton (diatom) blooms on the outer shelf. Phytoplankton production averages about 2 g C m−2 d−1 during upwelling events, and ‘new’ production is 50% or more of the total. When shelf waters are stratified, upwelled waters penetrate well onto the shelf as a subsurface intrusion in which phytoplankton production averages about fives times higher than the nutrient-depleted overlying mixed layer. Phytoplankton within the intrusion deplete upwelled NO3 in about 7 to 10 days, at which point no further net increase in phytoplankton biomass occurs.Current meter records show that upwelling occurs roughly 50% of the time on the outer shelf during November to April (shelf not stratified), and we estimate that seasonal primary production in upwelled waters is 175 g C m−2 6 months−1 of which at least 50% is ‘new’ production. More than 90% of outer shelf primary and ‘new’ production occurs during upwelling and thus upwelling is the dominant process affecting primary productivity of the outer shelf. Our seasonal estimates of outer shelf primary and ‘new’ production are, respectively, three and ten times higher than previous estimates that did not account for upwelling. 相似文献
109.
Particulate matter samples filtered from near-bottom, 30-liter water samples collected during the GEOSECS Atlantic cruise were analyzed by the Computer Evaluated Scanning Electron Microscope Image (CESEMI-2) system. This system permitted automated discrete particle analysis for the elements Al, Si, P, S, K, Ca, and Fe by energy-dispersive X-ray spectrometry and for particle size. Approximately 2000 particles in the size range 1–20 μm, representative of several milliliters of seawater, were analyzed per sample and yielded discrete size and chemical analysis of the major classes of particulate matter—opal, calcium carbonate, and clay—as well as some regularly occurring subclasses of clay and other minor classes.The distributional patterns of the major classes matched both in chemistry and abundance their general distributional patterns in sediments. Clay particles reflected high- and low-latitude sources; opal particles, patterns of diatom productivity; and carbonate, patterns of productivity as well as the calcite saturation chemistry of the water column. Superimposed on these features was evidence for long-range transport of particles in well-defined bottom water masses such as the Antarctic Bottom Water. Such transport is believed to occur through a series of resuspension events, in which case particle distributions match the properties of the sediments. Cases were found where near-bottom particles did not match the sediments, especially in quiescent environments. 相似文献
110.
Louise Levien Donald J. Weidner Charles T. Prewitt 《Physics and Chemistry of Minerals》1979,4(2):105-113
The thirteen single-crystal elastic moduli for diopside as determined by the acoustic technique based on Brillouin scattering are: c11=2.23, c22=1.71, c33=2.35, c44=0.74, c55=0.67, c66=0.66, c12=0.77, c13=0.81, c15=0.17, c23=0.57, c25=0.07, c35=0.43, c46=0.073. The Reuss bound of the adiabatic bulk and shear moduli calculated from these data are K s=1.08 Mbar and G=0.651 Mbar. The room-pressure isothermal bulk modulus, K T , and the pressure derivative of the bulk modulus, K′ T have also been determined on a four-circle diffractometer, from a single crystal mounted in a gasketed opposed-anvil diamond cell, giving values of K T =1.13 Mbar and K′ T =4.8. The principal axes of the strain ellipsoid, calculated from the elastic moduli and observed in the static compression data, are identical, and the linear compressibilities are in reasonable agreement. The single-crystal elastic moduli can be correlated with the structural features of diopside. 相似文献