Basic hydrology,limnology, and meteorology of modern Lake El’gygytgyn,Siberia

A survey of the modern physical setting of Lake El’gygytgyn, northeastern Siberia, is presented here to facilitate interpretation of a 250,000-year climate record derived from sediment cores from the lake bottom. The lake lies inside a meteorite impact crater that is approximately 18 km in diameter, with a total watershed area of 293 km², 110 km² of which is lake surface. The only surface water entering the lake comes from the approximately 50 streams draining from within the crater rim; a numbering system for these inlet streams is adopted to facilitate scientific discussion. We created a digital elevation model for the watershed and used it to create hypsometries, channel networks, and drainage area statistics for each of the inlet streams. Many of the streams enter shallow lagoons dammed by gravel berms at the lakeshore; these lagoons may play a significant role in the thermal and biological dynamics of the lake due to their higher water temperatures (>6°C). The lake itself is approximately 12 km wide and 175 m deep, with a volume of 14.1 km³. Water temperature within a column of water near the center of this oligotrophic, monomictic lake never exceeded 4°C over a 2.5 year record, though the shallow shelves (<10 m) surrounding the lake can reach 5°C in summer. Though thermally stratified in winter, the water appears completely mixed shortly after lake ice breakup in July. Mean annual air temperature measured about 200 m from the lake was −10.3°C in 2002, and an unshielded rain gage there recorded 70 mm of rain in summer of 2002. End of winter snow water equivalent on the lake was approximately 110 mm in May 2002. Analysis of NCEP reanalysis air temperatures (1948–2002) reveals that the 8 warmest years and 10 warmest winters have occurred since 1989, with the number of days below −30°C dropping from a pre-1989 mean of 35 to near 0 in recent years. The crater region is windy as well as cold, with hourly wind speeds exceeding 13.4 m s⁻¹ (30 mph) typically at least once each month and 17.8 m s⁻¹ (40 mph) in winter months, with only a few calm days per month; wind may also play an important role in controlling the modern shape of the lake. Numerous lines of evidence suggest that the physical hydrology and limnology of the lake has changed substantially over the past 3.6 million years, and some of the implications of these changes on paleoclimate reconstructions are discussed. This is the second in a series of eleven papers published in this special issue dedicated to initial studies of El'gygytgyn Crater Lake and its catchment in NE Russia. Julie Brigham-Grette, Martin Melles, Pavel Minyuk were guest editors of this special issue.     

运用生物地理学理论与遥感影像寻找本·拉登

本·拉登到底在哪里？这是我们这个时代最重要的政治问题之一。在这篇文章中,我们依据反映生物分布和灭绝规律的生物地理学理论(距离衰减理论、岛屿生物地理理论、本·拉登个人数据),结合遥感数据(陆地卫星 ETM+、航天雷达地形测图、QuickBird),从全球、区域、局部三个空间尺度分析并最终指出本·拉登当前最可能的所在地。这是第一次运用科学手段来确定本·拉登居所。该方法具有可重复性：一旦美国情报部门提供新的信息,便可通过该方法重新定位本·拉登当前最有可能的藏身场所。     

Radar and optical observations and physical modeling of triple near-Earth Asteroid (136617) 1994 CC

We report radar, photometric, and spectroscopic observations of near-Earth Asteroid (136617) 1994 CC. The radar measurements were obtained at Goldstone (8560 MHz, 3.5 cm) and Arecibo (2380 MHz, 12.6 cm) on 9 days following the asteroid’s approach within 0.0168 AU on June 10, 2009. 1994 CC was also observed with the Panchromatic Robotic Optical Monitoring and Polarimetry Telescopes (PROMPT) on May 21 and June 1-3. Visible-wavelength spectroscopy was obtained with the 5-m Hale telescope at Palomar on August 25. Delay-Doppler radar images reveal that 1994 CC is a triple system; along with (153591) 2001 SN263, this is only the second confirmed triple in the near-Earth population. Photometry obtained with PROMPT yields a rotation period for the primary P = 2.38860 ± 0.00009 h and a lightcurve amplitude of ∼0.1 mag suggesting a shape with low elongation. Hale telescope spectroscopy indicates that 1994 CC is an Sq-class object. Delay-Doppler radar images and shape modeling reveal that the primary has an effective diameter of 0.62 ± 0.06 km, low pole-on elongation, few obvious surface features, and a prominent equatorial ridge and sloped hemispheres that closely resemble those seen on the primary of binary near-Earth Asteroid (66391) 1999 KW4. Detailed orbit fitting reported separately by Fang et al. (Fang, J., Margot, J.-L., Brozovic, M., Nolan, M.C., Benner, L.A.M., Taylor, P.A. [2011]. Astron. J. 141, 154-168) gives a mass of the primary of 2.6 × 10¹¹ kg that, coupled with the effective diameter, yields a bulk density of 2.1 ± 0.6 g cm⁻³. The images constrain the diameters of the inner and outer satellites to be 113 ± 30 m and 80 ± 30 m, respectively. The inner satellite has a semimajor axis of ∼1.7 km (∼5.5 primary radii), an orbital period of ∼30 h, and its Doppler dispersion suggests relatively slow rotation, 26 ± 12 h, consistent with spin-orbit lock. The outer satellite has an orbital period of ∼9 days and a rotation period of 14 ± 7 h, establishing that the rotation is not spin-orbit locked. Among all binary and triple systems observed by radar, at least 25% (7/28) have a satellite that rotates more rapidly than its orbital period. This suggests that asynchronous configurations with P_rotation < P_orbital are relatively common among multiple systems in the near-Earth population. 1994 CC’s outer satellite has an observed maximum separation from the primary of ∼5.7 km (∼18.4 primary radii) that is the largest separation relative to primary radius seen to date among all 36 known binary and triple NEA systems. 1994 CC, (153591) 2001 SN263, and 1998 ST27 are the only triple and binary systems known with satellite separations >10 primary radii, suggesting either a detection bias, or that such widely-separated satellites are relatively uncommon in NEA multiple systems.     

Radar observations of Comet P/2005 JQ5 (Catalina)

Arecibo radar observations of Comet P/2005 JQ5 (Catalina) have produced the first delay-Doppler images of a comet nucleus and the first radar detection of large-grain ejection from a Jupiter-family comet. The nucleus is small (1.4 km diameter), rough, and rapidly rotating. The large (>cm) grains have low velocities (∼1 m/s) and a low production rate.     

Radar imaging of Asteroid 7 Iris

Arecibo radar images of Iris obtained in November 2006 reveal a topographically complex object whose gross shape is approximately ellipsoidal with equatorial dimensions within 15% of 253 × 228 km. The radar view of Iris was restricted to high southern latitudes, precluding reliable estimation of Iris’ entire 3D shape, but permitting accurate reconstruction of southern hemisphere topography. The most prominent features, three roughly 50-km-diameter concavities almost equally spaced in longitude around the south pole, are probably impact craters. In terms of shape regularity and fractional relief, Iris represents a plausible transition between ∼50-km-diameter asteroids with extremely irregular overall shapes and very large concavities, and very much larger asteroids (Ceres and Vesta) with very regular, nearly convex shapes and generally lacking monumental concavities.     

Tracer diffusion of some alkali,alkaline-earth and transition element ions in a basaltic and an andesitic melt,and the implications concerning melt structure

The diffusion properties of Na, Cs, Sr, Ba, Co, Mn, Fe and Sc ions in a basaltic and an andesitic melt have been determined experimentally using the radiotracer residual-activity method, and narrow platinum capillaries, over the temperature range 1,300–1,400° C. Diffusion of all cations follows an Arrhenius relationship; the values of the activation energies range from 24 kcal mol^–1 for Na to 67 kcal mol^–1 for Co in the andesitic melt, and from 39 kcal mol^–1 for Na to 65 kcal mol^–1 for Cs in the basaltic melt. Relative diffusivities in the basaltic melt, but not in the andesitic melt, correlate with assumed ionic radii values. Each cation, except Na⁺, diffuses faster in the basaltic melt than in the andesitic melt over the studied temperature range. Sodium shows similar diffusivity in the two melts.Compensation diagrams incorporating new and some previously-published data indicate that Cs probably diffuses by different mechanisms in different silicate glass and melt systems. Iron has a relatively high activation energy which is consistent with its part occupancy of tetrahedral co-ordination polyhedra.     

黄骅坳陷古近纪地震事件沉积研究

震积岩是地层中具有古地震事件记录的岩石.通过岩心观察和描述,在黄骅坳陷古近系中识别出震积岩,主要标志为同沉积变形构造,包括小规模阶梯状正断层、微褶皱纹理、振动液化砂泥岩脉、负荷构造、火焰构造等,通过单井岩心分析,建立了震积垂向序列.震积岩在单井岩心中重复出现,表明裂陷活动具有周期性和幕式特点.黄骅坳陷震积岩的发现为陆相断陷湖盆构造演化研究和震积岩的识别和描述提供了重要的依据,同时也具有一定的油气地质意义.     

Multifrequency studies of the enigmatic gamma-ray source 3EG J1835+5918

The EGRET telescope aboard the NASA Compton Gamma-Ray Observatory ( CGRO ) has repeatedly detected 3EG J1835+5918, a bright and steady source of high-energy gamma-ray emission which has not yet been identified. The absence of any likely counterpart for a bright gamma-ray source located 25° off the Galactic plane initiated several attempts of deep observations at other wavelengths. We report on counterparts in X-rays on a basis of a 60-ks ROSAT HRI image. In order to conclude on the plausibility of the X-ray counterparts, we reanalysed data from EGRET at energies above 100 MeV and above 1 GeV, including data up to CGRO observation cycle 7. The gamma-ray source location represents the latest and probably the final positional assessment based on EGRET data. We especially address the question of flux and spectral variability, here discussed using the largest and most homogeneous data set available at high-energy gamma-rays for many years. The results from X-ray and gamma-ray observations were used in a follow-up optical identification campaign at the 2.2-m Guillermo Haro Telescope at Cananea, Mexico. VRI imaging has been performed at the positions of all of the X-ray counterpart candidates, and spectra were taken where applicable. The results of the multifrequency identification campaign toward this enigmatic unidentified gamma-ray source are given, especially on the one object which might be associated with the gamma-ray source 3EG J1835+5918. This object has the characteristics of an isolated neutron star and possibly of a radio-quiet pulsar.