求回拍 argument50 彗星撞地球

芷琳UID: 2682149

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."



The author concludes that the water in Earth's oceans must have originated from comets. To support his conclusion ,he points out during the process of Earth's forming, the heat from collisions and increasing gravitational energy melted the entire planet, even the surface. Then ,he relies that striking earth will make comets 'frozen water and gases vaporize, and follows that the water in the Earth came from comets. I find this argument logically unconvincing in several respects.

First of all, the author assumes the collisions of comets must have happened after the forming of Earth. However, he fails to provide any science evidences about the forming time of Earth and the comets’ collision era. It is entirely possible that since Earth was formed, it had never occurred that comets stroke Earth. If it is the case , the comets would unlikely be molten in the collision procedure with Earth, and it follows that the water in Earth’ oceans unlikely stemmed from comets.

Secondly, even if comets once stroke earth, and they were evaporated, the author still fails to support that the water of oceans came from these periods. The author points out water present in
the initial collision with rocks would have evaporated and gone off into space. it is equally possible that the water and gases in the process of comets’ striking have vaporized into space, too. In this way, the author still cannot convince me that his claim about the origination of Earth' oceans is truthful.

Finally, even if the author can substantiate the foreseeing assumption, he ignores other possible explanation about causes of the oceans. It is totally probable that it is the chemical changing like kinds of elements’ reaction that produce the water in Earth. Without eliminating these possible factors, the conclusion is still unconvincing.

In sum, the conclusion is logically flawed and not well supported, therefore unconvincing as it stands. To strengthen this conclusion, the author should further supply the time of collision of Earth with rocks and comets to affirm the sequence of happening. And ruling out all other possible factors of oceans forming is essential. Only after wholly research, could the author convince me that the origination of Earth's oceans is comets.