Observations of Comet 9P/Tempel 1 with the Keck 1 HIRES instrument during Deep Impact     

Anita L. Cochran  William M. Jackson  Micah Glaz 《Icarus》2007,187(1):156-166

We report high-spectral resolution observations of Comet 9P/Tempel 1 before, during and after the impact on 4 July 2005 UT of the Deep Impact spacecraft with the comet. These observations were obtained with the HIRES instrument on Keck 1. We observed brightening of both the dust and gas, but at different rates. We report the behavior of OH, NH, CN, C₃, CH, NH₂ and C₂ gas. From our observations, we determined a CN outflow velocity of at least 0.51 km s⁻¹. The dust color did not change substantially. To date, we see no new species in our spectra, nor do we see any evidence of prompt emission. From our observations, the interior material released by the impact looks the same as the material released from the surface by ambient cometary activity. However, further processing of the data may uncover subtle differences in the material that is released as well as the time evolution of this material.  相似文献   

Investigating the Vesta-vestoid-HED connection     

Anita L Cochran  Faith Vilas 《Icarus》2004,167(2):360-368

We present spectral observations of Minor Planet 4 Vesta, of five V-type asteroids which are physically near Vesta, and of two V-type NEAs. We use these spectra to determine the presence or absence of a weak feature at 506.5 nm which is indicative of the presence of spin-forbidden Fe²⁺ in sixfold coordination. As with our earlier observations [Cochran and Vilas, Icarus 134 (1998) 207-212], we find this feature at all observed rotational phases of Vesta and again see the trend that spectra at longitudes between 240° and 360° have a smaller 506.5 nm feature equivalent width than spectra obtained at other longitudes. Additionally, we searched for this feature in V-class main-belt and NEA asteroids and positively detected the feature in main-belt Asteroid 2579 Spartacus and possibly in 3376 Armandhammer. The other objects lacked the feature. Our results are compared with previous observations of this feature by Vilas et al. [Icarus 147 (2000) 119-128]. The spatial distribution of the bodies as a function of the presence of this feature was investigated. We discuss the implication of the presence of this feature and the depth of the 0.9 μm pyroxene band for the scenario that pieces of Vesta were transported, via the 3:1 and ν₆ resonances, to the NEAs, and thence to inclusion in our meteorite collections as HED meteorites.  相似文献   

Dieter Stoeffler (1939–2023): Outstanding scientist,mentor, and friend     

Wolf Uwe Reimold  Natasha Artemieva  Lutz Hecht  Thomas Kenkmann  Falko Langenhorst  Knut Metzler  Kai Wünnemann 《Meteoritics & planetary science》2023,58(7):1056-1064

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The impact of El Ni?o on South American summer climate during different phases of the Pacific Decadal Oscillation     

Gyrlene Aparecida Mendes da Silva  Anita Drumond  T��rcio Ambrizzi 《Theoretical and Applied Climatology》2011,106(3-4):307-319

In austral summer, the observed El Ni?o (EN) events during warm Pacific Decadal Oscillation (PDO) phases (PDO(+)) exhibited large anomalous upper level wave patterns in response to larger Sea Surface Temperature (SST) anomalies in the Equatorial Pacific and Atlantic Oceans compared with SST anomalies in EN events during cold PDO phases (PDO(?)). The precipitation anomalies in PDO(+) EN are increased over Southeastern South America (SESA) associated with the intensification of the moisture flux convergence in this region. The PDO(?) EN events exhibit positive precipitation anomalies only over southern SESA, while negative anomalies were observed in the north. Downward motion and anomalous divergence over central eastern Brazil may have contributed to the weakening of the northwesterly moisture flux convergence associated with the South American Low Level Jet (SALLJ) over the subtropics. The extratropical cyclones showed higher frequency and lower central pressures in southern Brazil, Uruguay, northeastern Argentina, and Southwest Atlantic Ocean during the PDO(+) EN events compared with the PDO(?) EN events. Such increase in the frequency and intensity of cyclogenesis cases seems to be in accordance with the anomalous moisture flux convergence over the SESA and associated reduction in the Sea Level Pressure observed during PDO(+) EN events. In order to investigate the impact of a canonical El Ni?o event over South America under different PDO phases, two numerical experiments were done with an Atmospheric General Circulation Model. Global SST and ice sea fields average over years characterized by (a) PDO(+) and (b) PDO(?) were considered as climatologically fields, and a composite of anomalies of SST of all El Ni?o events observed in 1950?C1999 was added in the region 20oS?C20oN;120oW?C175oW of both ??climatologies.?? The differences in experiments suggest that a canonical EN may produce significant different anomalous atmospheric patterns associated with distinct PDO climatologies. The more significant differences are simulated over extreme northern and eastern Brazil. Additional numerical experiments isolating the observed variability of SST over several oceanic basins during different PDO phases will be conducted to study their particular role on the South American climate.  相似文献   

Sensitivity of DaisyGIS to LAI: Implications for land use based modelling of nitrate leaching     

Anita Veihe  Niels H. Jensen  Eva Boegh  Peter Frederiksen  Michael W. Pedersen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):75-85

Geografisk Tidsskrift, Danish Journal of Geography 106(2): 75–85, 2006

Scaling is an important issue when measuring, modelling and understanding coupled socio-environmental terrestrial systems. Scaling may be enhanced through the incorporation of remotely sensed data. This paper assesses the sensitivity of DaisyGIS to changes in the Leaf Area Index (LAI) and discusses the implications for land use based modelling of nitrate leaching using remote sensing based LAI estimates. It is shown how DaisyGIS simulates nitrate leaching quite well over the period 2001 to 2004 except for one plot during a season with winter rape. It was found that the model is sensitive to changes in LAI with increases of up to 262% on nitrate leaching rates when reducing LAI by 15%. At the same time, the nitrate leaching rates at the field level vary considerably due to local changes in the water balance determined by soil profile characteristics. DaisyGIS is already an important tool for aiding decision makers and this study has shown how remote sensing based LAI estimates may be a valuable tool for model parameterisation and potentially for model validation.  相似文献   

Power-Law Testing for Fault Attributes Distributions   总被引：2，自引：0，他引：2  

Dmitry Kolyukhin  Anita Torabi 《Pure and Applied Geophysics》2013,170(12):2173-2183

This paper is devoted to statistical analysis of faults’ attributes. The distributions of lengths, widths of damage zones, displacements and thicknesses of fault cores are studied. Truncated power-law (TPL) is considered in comparison with commonly used simple power-law (PL) (or Pareto) distribution. The maximal likelihood and the confidence interval of the exponent for both PL and TPL are estimated by appropriate statistical methods. The Kolmogorov–Smirnov (KS) test and the likelihood ratio test with alternative non-nested hypothesis for exponential distribution are used to verify the statistical approximation. Furthermore, the advantage of TPL is proved by Bayesian information criterion. Our results suggest that a TPL is more suitable for describing fault attributes, and that its condition is satisfied for a wide range of fault scales. We propose that using truncated power laws in general might eliminate or relax the bias related to sampling strategy and the resolution of measurements (such as censoring, truncation, and cut effect) and; therefore, the most reliable range of data can be considered for the statistical approximation of fault attributes.  相似文献   

Shock metamorphism of planetary silicate rocks and sediments: Proposal for an updated classification system          下载免费PDF全文

Dieter Stöffler  Christopher Hamann  Knut Metzler 《Meteoritics & planetary science》2018,53(1):5-49

We reevaluate the systematics and geologic setting of terrestrial, lunar, Martian, and asteroidal “impactites” resulting from single or multiple impacts. For impactites derived from silicate rocks and sediments, we propose a unified and updated system of progressive shock metamorphism. “Shock-metamorphosed rocks” occur as lithic clasts or melt particles in proximal impactites at impact craters, and rarely in distal impactites. They represent a wide range of metamorphism, typically ranging from unshocked to shock melted. As the degree of shock metamorphism, at a given shock pressure, depends primarily on the mineralogical composition and the porosity of a rock or sediment sample, different shock classification systems are required for different types of planetary rocks and sediments. We define shock classification systems for eight rock and sediment classes which are assigned to three major groups of rocks and sediments (1) crystalline rocks with classes F, M, A, and U; (2) chondritic rocks (class C); and (3) sedimentary rocks and sediments with classes SR, SE, and RE. The abbreviations stand for felsic (F), mafic (M), anorthositic (A), ultramafic (U), sedimentary rocks (SR), unconsolidated sediments (SE), and regoliths (RE). In each class, the progressive stages of shock metamorphism are denominated S1 to Sx. These progressive shock stages are introduced as: S1–S7 for F , S1–S7 for M, S1–S6 for A , S1–S7 for U , S1–S7 for C , S1–S7 for SR , S1–S5 for SE , and S1–S6 for RE . S1 stands for “unshocked” and Sx (variable between S5 and S7) stands for “whole rock melting.” We propose a sequence of symbols characterizing the degree of shock metamorphism of a sample, i.e., F-S1 to F-S7 with the option to add the tabulated pressure ranges (in GPa) in parentheses.  相似文献   

Climate change and community resilience in Samoa     

Anita Latai-Niusulu  Tony Binns  Etienne Nel 《Singapore journal of tropical geography》2020,41(1):40-60

Being resilient in the face of climate change seems especially important for island societies, which face the effects of rising temperatures, unpredictable rainfall, changing wind patterns and sea level rise. To date, most studies of adaptation and resilience among Pacific island communities have used indicators and methods rooted in Western science and neo-classical economics. These have been criticized as being locally irrelevant and inadequate to appreciate the dynamic nature and social structures of island communities and their capacity to adapt. This paper challenges the paradigm that defines resilience as a return to equilibrium, by using a non-equilibrium, cultural ecological lens. The non-equilibrium view of resilience sees the social systems of island nations as highly dynamic and undergoing persistent adaptation in the face of changing environmental factors. Field-based research undertaken in eight villages in Samoa found that, through constant exposure to environmental change over extended periods of time, communities have become resilient and are in a position to adapt to future changes. In developing future policy in relation to climate change, Pacific island governments need to develop a more nuanced understanding of islanders’ perceptions and historical actions in the context of both their physical locations and their dynamic socio-cultural systems.  相似文献   

Addendum to “Stöffler,D., Hamann,C., and Metzler,K., Shock metamorphism of planetary silicate rocks and sediments: Proposal for an updated classification system. Meteoritics & Planetary Science 53, 5–49, 2018”     

Dieter Stffler  Christopher Hamann  Knut Metzler 《Meteoritics & planetary science》2019,54(4):946-949

With this addendum we provide some correction and additional information regarding the above cited publication. It addresses the following two topics. (1) Clarification for a correct application of the criteria for certain shock stages of chondrites, in particular stage C‐S6. (2) Correction of a printing error in the table that contains the shock classification system of chondrites.  相似文献   

Assessing BTEX Biodegradation Potential at a Refinery Using Molecular Biological Tools     

Katherine C. Key  Kerry L. Sublette  Tyler W. Johannes  Dora Ogles  Brett Baldwin  Anita Biernacki 《Ground Water Monitoring & Remediation》2014,34(1):35-48

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