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Comets are now known to contain twice as many atoms of deuterium to
Comets are now known to contain twice as many atoms of deuterium to
游客
2025-02-22
32
管理
问题
Comets are now known to contain twice as many atoms of deuterium to
each atom of ordinary hydrogen found in seawater. Scientists have also
discovered that meteorites could not solely have delivered the water in the
Line ocean, for then the earth’s atmosphere would contain nearly 10 times as much
(5) xenon as it actually does, given that meteorites carry excess xenon. Hence, the
best model for the source of the oceans at the moment is a combination of water
derived from comets and water caught up in the rocky body of the earth as it
formed. This mixture satisfies both the xenon and deuterium problem, the
latter especially if the rocky material out near the earth’s present orbit
(10) collected some regularly composed local water from the solar nebula before they
accreted to form the earth. New laboratory studies have indicated that the
water vapor in the solar nebula would have had a low enough proportion of
deuterium to complement the excess deuterium found in comets. [br] According to the passage, scientists have concluded which of the following from the discovery of the large amount of deuterium found in comets?
选项
A、Comets do not contain enough deuterium to have solely created the Earth’s oceans.
B、Given the ratio of deuterium to ordinary hydrogen in seawater, comets cannot have contributed to the Earth’s oceans.
C、It is likely that comets contain less Xenon than meteorites do.
D、Given the low level of deuterium in the waters of Earth’s oceans, comets cannot be its sole source.
E、Comets now play a greater role in the creation of the Earth’s oceans than was previously thought.
答案
D
解析
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