Argument50 [AWB小组] 第九次作业

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The argument concludes that the water in Earth’s oceans must have originated from comets by several assumptions which seem logical. One can question those unwarranted premises and list other possibilities easily.

First of all, earth was being formed out of the collision of space rocks is just one of the several explanations on the original of the earth. Maybe the space dust and sand is absorbed and accumulated by a special core. With the time passing, the core forms the early earth and the water contained in the space dust and sand is kept on the earth for the sake of gravitation. Therefore the following reasoning that the water in the earth would have evaporated and gone off into space because of both the heat produced by the never existing collision and the increasing gravitational energy doesn’t make sense.

Secondly, even the earth was formed in the way stated by the author, how could he or she conclude that any water present would have evaporated and gone off into space？Maybe there would have been still some water left in the planet, if the evaporation had not been a global one. Or the heat from the collisions and from the increasing gravitational energy was not lasting, which led to some water evaporate while the rest wasn’t.

Thirdly, there is not any evidence to support the theory of the form of the atmosphere, especially providing it happened when the planet approached its current size. It is most probably that the atmosphere formed when the planet was smaller or bigger than what is now.

Fourthly, to judge that the water is from comets just for comets are largely ice made up of frozen water and gases is arbitrary. Maybe when the comet stake the earth, there was no atmosphere to remain the water vaporized so that no water from comets fell on the surface of Earth in the form of rain. It is perhaps some chemical reactions produce the water on the Earth.

In sum, the assumptions are not persuasive and there exist other possibilities to explain the source of the water in Earth’s oceans. If the author would like us to accept his or her opinion on the origin of the water, he or she has to exclude other possibilities and give explanation in detail.