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----题目----
50From a draft textbook manuscript submitted to a publisher.
"As Earth was being formed out of the collision of space rocks, the heat from those collisions and from the increasing gravitational energy of the planet made the entire planet molten, even the surface. Any water present would have evaporated and gone off into space. As the planet approached its current size, however, its gravitation became strong enough to hold gases and water vapor around it as an atmosphere. Because comets are largely ice made up of frozen water and gases, a comet striking Earth then would have vaporized. The resulting water vapor would have been retained in the atmosphere, eventually falling as rain on the cooled and solidified surface of Earth. Therefore, the water in Earth's oceans must have originated from comets."
----正文----
The manuscript get to the conclusion that the Earth's oceans must came from the collision of comets and Earth. I do highly doubt about the assertion made by the author through so-called reasons.
Firstly, what compound comets are still unknown to us. Though the author says that they are ice made up of frozen water and gases, which is still a hypothesis established in 1950 by an American astronomer, it has not been verified yet. Another American astronomer acclaimed that the composition of comets are rocks and other organic compounds this year in April, which is also a hypothesis to be proved. In the Independence Day NASA successfully conducted the mission Deep Impact with the spacecraft impacting into the comet Temple 1. One of the scientists' purposes is to determine the composition of comets by the depth of the crater: whether the comets are dirty snowballs or compound with hard organic material like rocks. We including the author have not realized the real composition of the comets, hastily concluding that the water in Earth came from comets seems greatly ungrounded.
Secondly, the manuscript assumes that the collisions caused the water retain in Earth. Though we concede that the comets are largely made up of frozen water and gases, the author provide no evidence to support this is the case, nor does he or she establish a causal relationship between the condition and the conclusion. If the gravitation was less powerful than the collisional energy, then the water and gases exploded from comets would entirely vaporized to the outer space rather than hold by Earth to form the ocean. The failure of the author to offer such significant necessity makes the manuscript vulnerable.
Moreover, if we acquiesce that the gravitation is much stronger than the collisional energy, and the water was really retain in Earth, however, we still do not know the times of the collisions and the strength of the collisions. As the Earth's oceans take almost 71 percent of the Earth's area, there should be collide how many times to accumulate such large quantity of water, the diameter of The Comet Temple 1 is only 6 kilometers, I've heard that some small comets only 12 meters in diameter. The author should make the data of the times of collisions and the strength of the collisions transparent to the readers to prove the conclusion, otherwise, it is unacceptable.
In sum, the author fails to demonstrate the composition of the comets and provide evidence of the contrast of the gravitation and the collisional energy, the manuscript is unconvincing as it stands.
这篇专业性也太强了吧~~~不知道频率如何呢?
也找了很多的资料看,作准备,终于写了430words,是argument写作以来最短的一篇了,还望大家拍,留链接互拍~~ |
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