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1. |
The lunar highlands crust |
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Eos, Transactions American Geophysical Union,
Volume 61,
Issue 22,
1980,
Page 473-475
Charles H. Simonds,
Claude T. Herzberg,
James J. Papike,
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摘要:
The heavily cratered lunar highlands (see cover) preserve remnants of the moon's origin at 4.5–4.6 billion years ago and subsequent evolution to 3.8–3.9 billion years ago. Rocks produced during the same time appear to be totally missing from the record on Earth. Thus the lunar highlands afford us the opportunity to study processes that were operative during planetary formation and early evolution; such studies can be expected to yield new insights on the history of the earth and other terrestrial planets during the first few hundred million years of their existence.Studies of the lunar highlands have made great strides since the collection of highland rocks by the Apollo 14,15,16, and 1 7 missions. Many types of information have been interpreted and synthesized, including petrologic and geochemical data collected on highlands samples and photographic and geochemical data, covering large portions of the moon's surface, collected by orbiting spacecraft. Research on igneous processes, such as fractional crystallization and magma mixing, has increased our understanding of lunar petrogenetic processes. Research on impact cratering processes (involving improved mathematical modeling, the study of small craters that are produced experimentally, and investigations of large terrestrial impact craters) has added greatly to our ability to interpret lunar history. In addition, the formulation of models of planetary accretion, heating, and internal mass transfer has increased our knowledge of the earliest processes of planetary format
ISSN:0002-8606
DOI:10.1029/EO061i022p00473
年代:1980
数据来源: WILEY
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2. |
Magsat to reenter soon |
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Eos, Transactions American Geophysical Union,
Volume 61,
Issue 22,
1980,
Page 475-475
Anonymous,
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摘要:
The Magsat satellite, successfully launched into a low‐altitude polar orbit on October 30, 1979, is expected to reenter the atmosphere in early June. The NASA satellite, designed to map the vector magnetic field near the earth, contains a cesium vapor scalar magnetometer of accuracy ±1 nT and three‐axis flux gate magnetometer of accuracy better than 3 nT (the earth's field at the surface ranges from 25,000 to 66,000 nT). The objectives of the mission are to provide a global vector survey of the main geopotential field and low‐altitude measurements of crustal anomalies (see ‘Near‐Earth Satellite Magnetic Field Measurements: A Prelude to Magsat,’ by R. A. Langel, EOS, 60, 38, 667–668, 1979).The mission was initially expected to have a 5‐month lifetime before reentering the atmosphere, according to a prediction made shortly after launch (see the Figure). This prediction used an atmospheric model appropriate to an average daily solar flux value at 10.7 cm (2800 MHz) of 200 flux units (1 flux unit = 10−22Wm−2Hz−1). Apogee and perigee heights, however, have declined more slowly than initially predicted, and the observed decay more closely fits a prediction based on 160 flux units. Thus a lifetime of approximately 7 mon
ISSN:0002-8606
DOI:10.1029/EO061i022p00475-01
年代:1980
数据来源: WILEY
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3. |
Another Moon for Jupiter |
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Eos, Transactions American Geophysical Union,
Volume 61,
Issue 22,
1980,
Page 476-476
Lee Greathouse,
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PDF (127KB)
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摘要:
Stephen P. Synnott of the Voyager Optical Navigation Team at the Jet Propulsion Laboratory in Pasadena has reported finding yet another moon of Jupiter—its 15th.The new‐found satellite, provisionally called 1979 J2, is estimated to be about 70 to 80 km in diameter and to have an orbit that places it between satellites Amalthea and Io, at a distance of about 151,000 km above the planet's clouds. The satellite circles the planet in 16 hours, 16 minu
ISSN:0002-8606
DOI:10.1029/EO061i022p00476-01
年代:1980
数据来源: WILEY
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