摘要:

An α particle experiment similar to the one performed successfully on the Surveyor lunar missions is described. It is designed to provide a chemical analysis of the Martian surface and atmosphere. A preprototype instrument significantly smaller than the Surveyor instrument has been constructed, and measurements demonstrating that the thin Martian atmosphere will not affect the analytical capabilities of the technique have been made. The density of the Martian atmosphere can be measured by such an instrument to better than 5%, and nitrogen, neon, and argon can be determined if the amounts are>1%. Analyses of rocks of known and unknown compositions have been made under simulated Martian conditions. The accuracies attained are generally comparable to those of the Surveyor lunar analyses. Improvements have been achieved in determining carbon and oxygen, so that a few per cent of water or carbonates in rocks can be detected. Some aspects of the integration of such an experiment with the spacecraft, a possible mission profile, and some other problems associated with a soft‐landing mission to Mars are discussed. The importance of such a chemical analysis experiment in answering current questions about the nature and history of Martian surface material and its suitability for life processes is present

ISSN:0148-0227    

DOI:10.1029/JB078i005p00781

年代:1973

数据来源: WILEY

摘要:

We present the photometric phase function, color, normal albedo, polarimetric phase function, and spectrophotometry of the Apollo 12 soil. With a few minor exceptions, the optical properties of the Apollo 12 soil are very similar to those of the Apollo 11 soil and of lunar mare surfaces.

ISSN:0148-0227    

DOI:10.1029/JB078i005p00792

年代:1973

数据来源: WILEY

摘要:

The residual field from Cosmos 49 is presented in chart form. This map displays vast areas (1000–4000 km across) of negative and positive ΔT(theTare differences between measured and model fields) that are of the order of a few tens of gammas. The external field does not exert any essential influence on the ΔTdistribution. The frequency spectrum of ΔTis similar to that of the model field used for the greater part of the chart, but within the ‘contrast zones’ the ΔTspectrum contains higher harmonics. There is no apparent correlation between the ΔTdistribution and near‐surface anomalies or the thickness of the magnetoactive layer of the earth's crust. The correlation with heat flow distribution is somewhat more distinct within certain regions. It appears that the greater part of ΔTis due to a poor representation of the main geomagnetic field. However, the authors do not exclude the possibility of intermediate anomalies of inductive origin within the mantle, which could contribute to the higher‐frequency part of

ISSN:0148-0227    

DOI:10.1029/JB078i005p00798

年代:1973

数据来源: WILEY

摘要:

Néel has derived an expression relating the decay of viscous remanent magnetization and the variation of susceptibility with frequency in noninteracting single‐domain assemblies of ferrimagnetic oxides, such as magnetite. This theory is extended to obtain a relationship for the quadrature susceptibility in such a sample. Measurements of these three parameters for soil samples and artificially prepared samples that contain single‐domain magnetite or maghemite grains are described; the results obtained are in good agreement with th

ISSN:0148-0227    

DOI:10.1029/JB078i005p00804

年代:1973

数据来源: WILEY

摘要:

Extensional and torsional velocities in granular aggregates were found to increase with confining pressure, while the associated fractional energy losses per cycle 2πQ−1decreased. Velocities of elastically deforming aggregates varied as the 1/3 power of pressure for aggregates of clean spherical particles, as the 1/3.5–1/5 power for lubricated spherical particles, and as the 1/4–1/6 power for clean and lubricated angular particles. Lubrication raised the velocities, at a given pressure, of the spherical particle aggregates but not of the angular particle aggregates. These results can be interpreted in terms of contact theory modified to include the changing number of interparticle contacts with pressure and lubrication. Also interpretable within the framework of contact theory is the observed decrease of velocity with decreasing spherical grain size and with increasing angularity. The velocity behavior in aggregates of plastically deforming particles, including the observation that the velocity becomes almost pressure independent above a certain pressure, can also be explained in terms of a modified contact theory. Values of Q−1for all aggregates were independent of vibration frequency (1–20 kHz) and essentially independent of vibration amplitude over the range studied. Lubrication generally increased relative energy losses, sometimes by a factor of 10. The energy dissipation at low pressures, which is thought to be related to lightly made contacts, is not adequately described by any present theory. The measured extensional velocities of clean aggregates at pressures of about 1 bar ranged from about 0.3 to 0.6 km/sec, and the associated values of Q−1ranged from about 4 × 10−3to 2 × 10−2. Extrapolations of these values to appropriate lunar conditions compare favorably with the velocities and the Q−1values reported in a study of man‐ma

ISSN:0148-0227    

DOI:10.1029/JB078i005p00810

年代:1973

数据来源: WILEY

摘要:

Differentiation of crust and mantle components during ascent between steadily diverging plates follows a simple law independent of the shape of the conduit and the spreading velocity under fairly general conditions. If the upward velocities of crust and mantle components are of the same order of magnitude, the rising column contains two to four times as much crustal material as the lithosphere that it creates. This paradox, which is unique to a spreading system, can substantially influence estimates of the gravitational driving pressure for the ascent of new material beneath an oceanic ridge. The model also implies that the lithosphere is enriched in crustal component relative to its source in the asthenosphere by the ratio of the upward velocities of the crust and mantle components.

ISSN:0148-0227    

DOI:10.1029/JB078i005p00825

年代:1973

数据来源: WILEY

摘要:

Geodetic data along the San Andreas fault between Parkfield and San Francisco, California (latitudes 36°N and 38°N, respectively), have been re‐examined to estimate the current relative movement between the American and Pacific plates across the San Andreas fault system. The average relative right lateral motion is estimated to be 32 ± 5 mm/yr for the period 1907–1971. Between 36°N and 37°N it appears that most, if not all, of the plate motion is accommodated by fault creep. Although strain is presumably accumulating north of 37°N (San Francisco Bay area), the geodetic evidence for accumulation is not c

ISSN:0148-0227    

DOI:10.1029/JB078i005p00832

年代:1973

数据来源: WILEY

摘要:

A group of short, linear structural depressions occurs in the Wharton basin in the northeast Indian Ocean. Depth to acoustic basement exceeds 7500 meters in at least one of the deeps. Bathymetric and seismic data indicate that the deeps may be grabens produced by crustal extension and thinning. Another possibility is that they may be fracture zones associated with an extinct (and ill‐defined) spreading center that have been disoriented by crustal motions subsequent to their emplacemen

ISSN:0148-0227    

DOI:10.1029/JB078i005p00846

年代:1973

数据来源: WILEY

摘要:

A 152‐meter‐deep well was drilled into the San Andreas fault zone near Hollister, California, to examine the possibility of any variations in fluid pore pressure during fault creep movement. Anomalous water level changes were recorded that coincide, within hours, with the only creep episodes recorded at a nearby site. The ratio of maximum water level change to total creep offset observed is 14 mm/mm. The calculated change in pore pressure for creep events is about 20 mb. Assuming 1.2 cm of total creep displacement per year along this section of the San Andreas fault, we obtain a total stress drop of 60 mb/yr associated with creep at shallow depths. The results are most encouraging, indicating the possibility that deeper wells could be used to monitor stress changes along active fault zo

ISSN:0148-0227    

DOI:10.1029/JB078i005p00851

年代:1973

数据来源: WILEY

摘要:

Two pairs of lights are being photographed with a camera of 10–meter focal length, one pair on each side of the transform fault between Angel de la Guarda Island and the Baja California peninsula, which is a part of the East Pacific rise. During the winter the average of about 150 photographs defines the angle between the near and far lights with a probable error of 0.01 arc sec (5 × 10−8rad), which is the customary precision astronomers get for parallaxes of stars with long‐focus photographic telescopes. This corresponds to detection with 95% confidence of a 4–mm fault displacement at the distance of the far station, 25 km from the camera, or 0.07 of the annual spreading rate of the gulf averaged over the last 5 m.y. Between March 1970 and March 1972 neither displacement nor strain accumulation has been detected; this result can be interpreted as the locking of the fault in a thick lithosphere. The lights, powered by small solar cell panels, need no attention and are ideal for remote mountain peaks. The camera is automatic and could be serviced once a month. The method can continuously monitor earth displacement in inaccessible terrain better than the geodimeter because a great number of measurements can be made at

ISSN:0148-0227    

DOI:10.1029/JB078i005p00858

年代:1973

数据来源: WILEY