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排序方式: 共有199条查询结果,搜索用时 375 毫秒
1.
Jose A.P. Rodriguez Sho Sasaki James M. Dohm Hideaki Miyamoto Goro Komatsu Justin C. Ferris 《Icarus》2005,175(1):36-57
The undulating, warped, and densely fractured surfaces of highland regions east of Valles Marineris (located north of the eastern Aureum Chaos, east of the Hydraotes Chaos, and south of the Hydaspis Chaos) resulted from extensional surface warping related to ground subsidence, caused when pressurized water confined in subterranean caverns was released to the surface. Water emanations formed crater lakes and resulted in channeling episodes involved in the excavation of Ares, Tiu, and Simud Valles of the eastern part of the circum-Chryse outflow channel system. Progressive surface subsidence and associated reduction of the subsurface cavernous volume, and/or episodes of magmatic-driven activity, led to increases of the hydrostatic pressure, resulting in reactivation of both catastrophic and non-catastrophic outflow activity. Ancient cratered highland and basin materials that underwent large-scale subsidence grade into densely fractured terrains. Collapse of rock materials in these regions resulted in the formation of chaotic terrains, which occur in and near the headwaters of the eastern circum-Chryse outflow channels. The deepest chaotic terrain in the Hydaspis Chaos region resulted from the collapse of pre-existing outflow channel floors. The release of volatiles and related collapse may have included water emanations not necessarily linked to catastrophic outflow. Basal warming related to dike intrusions, thermokarst activity involving wet sediments and/or dissected ice-enriched country rock, permafrost exposed to the atmosphere by extensional tectonism and channel incision, and/or the injection of water into porous floor material, may have enhanced outflow channel floor instability and subsequent collapse. In addition to the possible genetic linkage to outflow channel development dating back to at least the Late Noachian, clear disruption of impact craters with pristine ejecta blankets and rims, as well as preservation of fine tectonic fabrics, suggest that plateau subsidence and chaos formation may have continued well into the Amazonian Period. The geologic and paleohydrologic histories presented here have important implications, as new mechanisms for outflow channel formation and other fluvial activity are described, and new reactivation mechanisms are proposed for the origin of chaotic terrain as contributors to flooding. Detailed geomorphic analysis indicates that subterranean caverns may have been exposed during chaos formation, and thus chaotic terrains mark prime locations for future geologic, hydrologic, and possible astrobiologic exploration. 相似文献
2.
Joji Ishizaka Yasuhisa Kitaura Yasuharu Touke Hiroaki Sasaki Akihiko Tanaka Hiroshi Murakami Toshikazu Suzuki Kazumi Matsuoka Hideaki Nakata 《Journal of Oceanography》2006,62(1):37-45
High resolution SeaWiFS data was used to detect red tide events that occurred in the Ariake Sound, Japan, a small embayment
known as one of the most productive areas in Japan. SeaWiFS chlorophyll data clearly showed that a large red tide event, which
damaged seaweed (Nori) cultures, started early in December 2000 in Isahaya Bay, expanded to the whole sound and persisted
to the end of February 2001. The monthly average of SeaWiFS data from May 1998 to December 2001 indicated that the chlorophyll
peaks appeared twice a year, in early summer and in fall, after the peaks of rain and river discharge. The SeaWiFS data showed
that the red tide event during 2000–2001 winter was part of the fall bloom; however, it started later and continued significantly
longer than other years. Satellite ocean color data is useful to detect the red tide; however the algorithms require improvement
to accurately estimate chlorophyll in highly turbid water and in red tide areas. 相似文献
3.
Using a two-dimensional primitive equation model, we examine nonlinear responses of a semidiurnal tidal flow impinging on
a seamount with a background Garrett-Munk-like (GM-like) internal wavefield. It is found that horizontally elongated pancake-like
structures of high vertical wavenumber near-inertial current shear are created both in the near-field (the region over the
slope of the seamount) and far-field (the region over the flat bottom of the ocean). An important distinction is that the
high vertical wavenumber near-inertial current shear is amplified only at mid-latitudes in the far-field (owing to a parametric
subharmonic instability (PSI)), whereas it is amplified both at mid-and high-latitudes (above the latitude where PSI can occur)
in the near-field. In order to clarify the generating mechanism for the strong shear in the near-field, additional numerical
experiments are carried out with the GM-like background internal waves removed. The experiments show that the strong shear
is also created, indicating that it is not caused by the interaction between the background GM-like internal waves and the
semidiurnal internal tides. One possible explanation is proposed for the amplification of high vertical wavenumber near-inertial
current shear in the near-field where tide residual flow resulting from tide-topography interaction plays an important role
in transferring energy from high-mode internal tides to near-inertial internal waves. 相似文献
4.
In order to determine why the sedimentation to supply ratio of nutrients in Tokyo Bay is markedly small, the nitrogen budget was investigated for 1979, when a systematic and continuous observation of flow and salinity was carried out. The data were analyzed by use of a simple advective-diffusive box model and dissolved oxygen balance in the lower layer was also examined. The calculated values of two-layer flow, settling, primary production, mineralization, denitrification, and dissolved oxygen consumption were comparable to those observed.The factors making the sedimentation to supply ratio makedly small were summarized as: 1) a strong and stable two-layer flow generated by a large freshwater supply, 2) further intensification of this two-layer flow by the northern winter monsoon, 3) coincidence of the discharge region with the supply region of nutrients caused by the transverse inclination of the interface, probably due to the earth's rotation. 4) effective discharge of nutrients from the bay due to a strong tidal flow and a possible cyclonic tidal residual circulation in the inner bay mouth, 5) incomplete consumption of nutrient salts by phytoplankton in the upper layer even in the most productive season, and 6) possible denitrification in the anaerobic bottom water in summer and in the bottom sediment itself throughout the year in the inner bay. 相似文献
5.
Vertical distribution of anthropogenic carbon content of the water (exDIC) in the Oyashio area just outside of the Kuroshio/Oyashio Interfrontal Zone (K/O Zone) was estimated by the simple 1-D advection-diffusion model calibrated by the distribution of chlorofluorocarbons (CFCs). The average concentration of exDIC for = 26.60–27.00 is multiplied by the volume transport of Oyashio water into the North Pacific Intermediate Water (NPIW) to estimate the annual transport of exDIC into NPIW through K/O Zone. The estimated transport of exDIC was 0.018–0.020 GtC/y, which corresponds to 15% of the whole total exDIC accumulation in the temperate North Pacific. A simple assessment using the NPIW 1-box model indicates that the current study explains at least 70% of the total annual transport of exDIC into NPIW, and that small exDIC sources for NPIW still exists in addition to K/O Zone. 相似文献
6.
Numerical solutions of irrotational, progressive surface gravity waves in water of a constant depth are obtained by means of an iterative method. Our results suggest that waves with the surface slope angle greater than/6 may exist. The calculated phase velocity of deep water waves near the wave steepness 0.14 is significantly smaller than the value given by the Stokes' fourth approximation.In order to check our method, we apply it to the problem proposed byDavies (1951), which is hypothetical but similar to the present problem, and for which the exact solution is known. In this case our results show good agreement with the exact solution. 相似文献
7.
Sho Sasaki 《Astrophysics and Space Science》1994,212(1-2):33-41
When planetary accretion proceeds in the gas disk-solar nebula, a protoplanet attracts surrounding gas to form a distended H2-He atmosphere. The blanketing effect of the atmosphere, hampering the escape of accretional energy, enhances the surface temperature of planets. Furthermore, evaporation of ice or reduction of surface silicate and metallic oxide can supply a huge amount of water vapor into the atmosphere, which would raise the temperature and promote evaporation. Evaporated materials can be efficiently conveyed outward by vigorous convection, and condensed dust particles should keep the atmosphere opaque during accretion. The size of this opaque atmosphere dust blob is defined by the gravitational radius, which exceeds 3 × 108 m when the planetary mass is the Earth's mass (5.97 × 1024 kg). This is larger than the radii of present Jovian planets and so-called brown dwarfs. The expected lifetime of dust blobs is 106–107 yr, which is longer than that of the later gas accreting and cooling stages of Jovian planets. The number of dust blobs could exceed that of Jovian planets. If the gas disk is rather transparent, the possibility of observing such objects with a distended atmosphere may be higher than that of detecting Jovian planets. Contamination of the gas disk by the dust from primary atmospheres is negligible.Paper presented at the Conference on Planetary Systems: Formation, Evolution, and Detection held 7–10 December, 1992 at CalTech, Pasadena, California, U.S.A. 相似文献
8.
Nobuki Kawashima Susumu Sasaki Osamu Kaneko Akira Yamori Ryo Okamura Shoichi Okamura 《Planetary and Space Science》1978,26(4):367-373
A controlled active experiment was performed by a plasma gun on-board a rocket to study the plasma stream across the magnetic field in space. A mother and daughter system was employed. An 8 kV 0.8 μF (25 J) capacitor bank on the daughter rocket was discharged every 12 s and about 1016 ion and electron pairs were ejected. A plasma signal was detected on the electron temperature probe. The propagation speed of the plasma stream is estimated to be 106 cm/s, considerably lower than that obtained in the prelaunch test. The amplitude of the plasma signal decays as the inverse square of the mutual distance between the mother and daughter rockets and this decay is much slower than the free streaming. The importance of the geomagnetic field on the plasma propagation in space is discussed. 相似文献
9.
Infrared (IR) and nearinfrared (NIR) absorption spectra of hydrous and F-rich topazes were measured to assign an OH bending
mode of topaz. Three absorption peaks at 1165, 3650, and 4803 cm−1 are assigned to OH related absorption peaks. Since a peak at 4803 cm−1 can be assigned to a combination mode of 1165 and 3650 cm−1, the 1165 cm−1 peak is harmonic with the 3650 cm−1 peak. Polarized IR absorption spectra of (100), (010), and (001) planes of the hydrous topaz were measured to examine IR
active orientation of the 1165 cm−1 OH related mode. Three pleochroic distributions of the absorption peak at 1165 cm−1 on (100), (010), and (001) planes indicate an active orientation of the 1165 cm−1 OH related mode. The IR active orientation of the 1165 cm−1 OH related mode in topaz is normal to the OH dipole. The orthogonality and harmonic combination mode indicate that the 1165 cm−1 peak is OH bending mode. The active orientation of OH bending mode is polarized in the plane normal to the OH dipole. The
polarization suggests that anisotropic thermal vibration of protons on the hydroxyl is maximum along the IR active orientation.
Received: August 16, 1996 / Revised, accepted: April 20, 1997 相似文献
10.