0910AW 同主题写作第十五期 ARGUMENT50 by 尾羽

尾羽UID: 2482591

TOPIC: ARGUMENT50 - From 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."
WORDS: 433          TIME: 00:47:18（看题目就看了很久。。。）          DATE: 2009-8-14 21:43:46

Basing on the fact that Earth was being formed out of the collision of space rocks and the resulting heat would evaporate any presented water into space, and supposing that after the earth's size approached as same as current one's with strong enough gravity to hold gases and water, a comet would be evaporated and then retain its water in the atmosphere, the author accordingly concludes that the water in Earth's oceans must have originated from comets. It seems to be a rational deduction, while a close examination would reveal how groundless it is.

A threshold assumption upon which this argument relies on is that comets are largely ice made up of frozen water and gases, a comet striking Earth then would have vaporized. Nevertheless, there is no guarantee that it is necessarily the case and it is entirely possible that the frozen water and gases of comet was evaporated exhaustively far away from the Earth because of the extremely high temperature of the Earth, and then the earth had not sufficient powerfully gravity to hold the water around it which is too far. Thus, to improve efficiency, the author must present more information about comet like something above, otherwise suspicions to the study would be brought out.

What further weakens the conclusion in this argument is the factor that the resulting water vapor would have been retained in the atmosphere. Consider the hot Earth at that time, an appropriate probability is not very far to seek: the atmosphere around the Earth could not be generated because no evidence is presented to indicate that the Earth had been cooled down to the temperature to allow the evaporated water maintains around it before the comet evaporated water was falling as rain -some weak and ambiguous information is merely thrown into the argument.

Moreover, even assuming that all the deduction mentioned foregoing might be possible, the author still cannot substantiate the assumption to be warranted that the Earth's oceans must originated form comets. It might be possibility that other space substance maintaining frozen water and gases to collide the Earth- the author neglect to consider other possibilities. Under any scenario, adopting the author's proposal might not be persuasive.

As it stands, the conclusion of this argument is not well reasoned. To make it more logically acceptable, the author would have to demonstrate detailed investigations with solid facts that how the Earth was be cooled down for ready to allow the rain falling down and more appropriate deduction that whether the comet is the unique object could result in the Earth's oceans in the way mentioned above