Farmington Meteorite: A fragment of an Apollo asteriod?     

B.J. Levin  A.N. Simonenko  Edward Anders 《Icarus》1976,28(3):307-324

We have attempted to reconstruct the orbit of the Farmington L5 chondrite which fell in Kansas in 1890. Because its radiation age is uniquely short (25 000 years), its orbit should still closely resemble that of its parent body. A search of 280 contemporary newspapers and other sources turned up more than 60 useable eyewitness reports from 32 localities, which led to the following estimate of the apparent radiant: height 60°, azimuth 20°, with an uncertainty of about 10°. Orbital elements were determined for this radiant for four plausible preatmospheric velocities: 13, 16, 19, and 22 km/sec. The results show quite definitely that Farmington had a small orbit of low inclination: semimajor axis 1–1.9 AU, perihelion ? 0.4 AU, aphelion ? 3.0 AU, inclination ? 16°. Because of the short radiation age, the parent body of Farmington must already have been in an Earth-crossing orbit when the meteorite was ejected from it by an impact. Of the 11 known Earth-crossing asteroids with encounter velocities below 22 km/sec, 1862 Apollo, Hermes, and 1865 Cerberus are passable matches, while 1620 Geographos and 1685 Toro are more marginal possibilities. Apparently Earth-crossing asteroids are the immediate parent bodies of at least some meteorites. Their ultimate source must be the ultimate source of most stony meteorites.  相似文献   

THE TOULON METEORITE: A NEW CHONDRITE FROM ILLINOIS     

Edward Olsen  Glenn I Huss 《Meteoritics & planetary science》1974,9(1):19-22

Toulon is an olivine-bronzite chondrite found near Toulon, Illinois in 1962. It contains abundant, well preserved chondrules, as well as glasses that are not well devitrified. Most of the metal has been weathered out. Olivine and pyroxene are well equilibrated. We have classified it as an H5 chondrite.  相似文献   

Charge-coupled device photometry of Comet P/Halley     

David Jewitt  G. Edward Danielson 《Icarus》1984,60(3):435-444

Comet P/Halley has been observed during its approach to perihelion at heliocentric distancesR = 11.0 AU and R = 8.2 AU. No extended coma is seen and limits can be placed on the fraction of the total light contributed by coma. The brightness of the comet varies on a short time scale. The variations may be due to transient activity or to rotation of the irregular nucleus.  相似文献   

SUMMARY OF SEVERAL RECENT CHONDRITE FINDS FROM THE TEXAS PANHANDLE     

Paul S. Sipiera  Edward J. Olsen  Dorothy L. Eatough  Bruce D. Dod 《Meteoritics & planetary science》1983,18(1):63-75

Eleven recent chondrite finds from the Texas Panhandle have been examined and classified according to mineralogical and petrological criteria: five H's, five L's, and one LL chondrite. Five are distinct from nearby finds, while three remain ambiguous and three are related to previously reported chondrites. In addition, data are provided to classify the Muleshoe, Silverton, and Vigo Park chondrites, all of which were previously undescribed in the literature.  相似文献   

The performance of the Apache Point Observatory 3.5 m telescope     

Edward J. Mannery  Walter A. Siegmund  Charles L. Hull 《Astrophysics and Space Science》1989,160(1-2):269-274

The Astrophysical Research Consortium 3.5 m telescope facility on Apache Point (2800 m above sea level) near the National Solar Observatory in southern New Mexico is nearing completion. The telescope mount has been installed and testing and fabrication of remaining subassemblies are underway. Thef/1.75 lightweight honeycomb primary mirror was cast April 1988 by the Steward Observatory Mirror Laboratory and is currently being figured.The 3.5 m optical telescope is an altitude over azimuth mechanical structure with Ritchey-Chrétien optics. The lightweight (1800 kg) mirror leads to a mount weighting only 41000 kg; readily available rolling element bearings are used to achieve the necessary performance at low cost and without the heat dissipation of externally pressurized types. Drive torques are applied by DC servo-driven capstans. These are coupled by friction to large diameter drive disks on each axis. No gears are used. Position feedback comes from low cost incremental encoders, also capstan coupled.We have recently completed a series of measurements of the telescope mount. These measurements show that the telescope is very stiff; the lowest natural frequencies are about 7.2 Hz. Initial tracking performance is good and the mount shows high resistance to wind-induced vibration. Our experience during acceptance testing suggests that routine power spectral analysis of drive motor torque and other parameters could be an important tool in the early detection of failures.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.  相似文献   

The magnetic structure of arch filament systems   总被引：1，自引：0，他引：1  

Edward N. Frazier 《Solar physics》1972,26(1):130-141

Photographic-type magnetograms are used in conjunction with H filtergrams to study the structure and evolution of magnetic fields associated with arch filament systems. The magnetograms show that the opposite ends of the arch filaments are indeed rooted in photospheric magnetic fields of opposite polarity. Furthermore, these magnetic field systems are in every case new magnetic flux appearing at the solar surface. Time lapse studies show the detailed process by which the flux tubes emerge through the surface. First, supergranules bring individual strands of magnetic flux to the surface and sweep the two feet of the flux tube to opposite sides of the supergranule. Then, the flux tube rises through the chromosphere, creating a visible arch filament. It is also shown that the observed rotation of the axis of an arch filament system in the plane of the solar surface is caused by the emergence of successive flux loops, each possessing different axial tilts.  相似文献   

Fast Frequency-Wavenumber Analysis and Fisher Signal Detection in Real-Time Infrasonic Array Data Processing     

Eugene Smart  Edward A. Flinn 《Geophysical Journal International》1971,26(1-4):279-284

Summary A high speed algorithm for computation of frequency-wavenumber (f-k) spectra is developed, and two real-time infrasonic data processing techniques that it makes possible, are described: (1) Signal detection by a search of f-k space. This process is compared to the N-4 correlator, a broad-band signal detector. The f-k search with a Fisher detector has a theoretical advantage, which we verify in practice. (2) An f-k filter technique for calculating 'best beam' estimates. This technique traces the beam containing maximum power, from frequency to frequency through f-k space, and thus allows for wandering of signal velocity and arrival azimuth. This maximum power function is taken as the frequency spectrum of the best beam. In our programs the Fisher statistic of the signal estimate, and the velocity and azimuth, are computed and displayed as functions of frequency. Examples from real data for both processing techniques are discussed.  相似文献   

The M‐/X‐asteroid menagerie: Results of an NIR spectral survey of 45 main‐belt asteroids     

Paul S. HARDERSEN  Edward A. CLOUTIS  Vishnu REDDY  Thais MOTHÉ‐DINIZ  Joshua P. EMERY 《Meteoritics & planetary science》2011,46(12):1910-1938

Abstract– Diagnostic mineral absorption features for pyroxene(s), olivine, phyllosilicates, and hydroxides have been detected in the near‐infrared (NIR: approximately 0.75–2.50 μm) spectra for 60% of the Tholen‐classified ( Tholen 1984, 1989 ) M‐/X‐asteroids observed in this study. Nineteen asteroids (42%) exhibit weak Band I (approximately 0.9 μm) ± Band II (approximately 1.9 μm) absorptions, three asteroids (7%) exhibit a weak Band I (approximately 1.05–1.08 μm) olivine absorption, four asteroids (9%) display multiple absorptions suggesting phyllosilicate ± oxide/hydroxide minerals, one (1) asteroid exhibits an S‐asteroid type NIR spectrum, and 18 asteroids (40%) are spectrally featureless in the NIR, but have widely varying slopes. Tholen M‐asteroids are defined as asteroids exhibiting featureless visible‐wavelength (λ) spectra with moderate albedos ( Tholen 1989 ). Tholen X‐asteroids are also defined using the same spectral criterion, but without albedo information. Previous work has suggested spectral and mineralogical diversity in the M‐asteroid population ( Rivkin et al. 1995, 2000 ; Busarev 2002 ; Clark et al. 2004 ; Hardersen et al. 2005 ; Birlan et al. 2007 ; Ockert‐Bell et al. 2008, 2010 ; Shepard et al. 2008, 2010 ; Fornasier et al. 2010 ). The pyroxene‐bearing asteroids are dominated by orthopyroxene with several likely to include higher‐Ca clinopyroxene components. Potential meteorite analogs include mesosiderites, CB/CH chondrites, and silicate‐bearing NiFe meteorites. The Eos family, olivine‐bearing asteroids are most consistent with a CO chondrite analog. The aqueously altered asteroids display multiple, weak absorptions (0.85, 0.92, 0.97, 1.10, 1.40, and 2.30–2.50 μm) indicative of phyllosilicate ± hydroxide minerals. The spectrally featureless asteroids range from metal‐rich to metal‐poor with meteorite analogs including NiFe meteorites, enstatite chondrites, and stony‐iron meteorites.  相似文献   

Mineralogical characterization of Baptistina Asteroid Family: Implications for K/T impactor source     

Vishnu Reddy  Jorge M. Carvano  Daniela Lazzaro  Tatiana A. Michtchenko  Michael J. Gaffey  Michael S. Kelley  Thais Mothé-Diniz  Alvaro Alvarez-Candal  Nicholas A. Moskovitz  Edward A. Cloutis  Erin L. Ryan 《Icarus》2011,216(1):184-197

Bottke et al. [Bottke, W.F., Vokrouhlicky, D., Nesvorný, D., 2007. Nature 449, 48–53] linked the catastrophic formation of Baptistina Asteroid Family (BAF) to the K/T impact event. This linkage was based on dynamical and compositional evidence, which suggested the impactor had a composition similar to CM2 carbonaceous chondrites. However, our recent study [Reddy, V., Emery, J.P., Gaffey, M.J., Bottke, W.F., Cramer, A., Kelley, M.S., 2009. Meteorit. Planet. Sci. 44, 1917–1927] suggests that the composition of (298) Baptistina is similar to LL-type ordinary chondrites rather than CM2 carbonaceous chondrites. This rules out any possibility of it being related to the source of the K/T impactor, if the impactor was of CM-type composition. Mineralogical study of asteroids in the vicinity of BAF has revealed a plethora of compositional types suggesting a complex formation and evolution environment. A detailed compositional analysis of 16 asteroids suggests several distinct surface assemblages including ordinary chondrites (Gaffey SIV subtype), primitive achondrites (Gaffey SIII subtype), basaltic achondrites (Gaffey SVII subtype and V-type), and a carbonaceous chondrite. Based on our mineralogical analysis we conclude that (298) Baptistina is similar to ordinary chondrites (LL-type) based on olivine and pyroxene mineralogy and moderate albedo. S-type and V-type in and around the vicinity of BAF we characterized show mineralogical affinity to (8) Flora and (4) Vesta and could be part of their families. Smaller BAF asteroids with lower SNR spectra showing only a ‘single’ band are compositionally similar to (298) Baptistina and L/LL chondrites. It is unclear at this point why the silicate absorption bands in spectra of asteroids with formal family definition seem suppressed relative to background population, despite having similar mineralogy.  相似文献   

Capturing the Atlantic cold tongue and coastal upwelling in an intermediate-level ocean model coupled to a regional climate model     

Edward K. Vizy  Kerry H. Cook 《Climate Dynamics》2014,42(1-2):345-366

Coupled atmosphere–ocean general circulation models are known to have difficulties simulating the cold tongue in the equatorial Atlantic Ocean. Here a regional climate model coupled to an intermediate-level mixed layer ocean model with Ekman dynamics is developed and used to better understand the seasonal evolution of the equatorial Atlantic cold tongue and upwelling off western Africa. Parameterization improvements are made to an earlier version of the ocean model to account for the variations in temperature and shearing stress at the base of the mixed layer. 90-km resolution sensitivity tests demonstrate that the development of the equatorial Atlantic cold tongue in the boreal spring/summer is captured only if seasonal variations in the temperature at the base of the ocean mixed layer are included. The development of cold temperatures off the northwest African coast in the late boreal winter/spring is found to be primarily associated with the net radiation balance as shortwave warming of the mixed layer is relatively low while latent cooling is relatively high yielding a net cooling of mixed layer temperatures, consistent with other studies. The westward extension of the Atlantic cold tongue is primarily due to the horizontal advection of cool water from the South Atlantic African coast. This coastal cooling is associated with vertical diffusion and vertical entrainment, while the vertical entrainment has a secondary and more localized role over the equatorial Atlantic.  相似文献