【Flyer小组习作】argument50-7.16

MaryWongUID: 2619999

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: 366
TIME: 00:30:00


The author assumes unfairly a cause-effect correlation between comets and generation of Earth. And the argument does not offer enough material on the specific information of comets and other possibilities of origine of water in the Earth.

To begin with, the evidence that Earth striking comet is not suffice to demonstrate that the water can be hold in earth. Although the argument provides the statistic that when the planet approached size like nowadays it would be able to hold gases and water vapor. There is not any evidenct shows that comet striked Earth when Earth has reached its current size. Lacking such evidence it is equally to say that even if comet, which is almost ice, striked Earth, there is still not enough gravitation for Earth to keep the water and gases from comet since Earth's small size.

Secondly, even if the assumption the author made is convinced, there is not persuasive evidence shows that Earth's oceans water come from the striking with comet. Common sense informs us that there are so many oceans in Earth and the water in oceans account for over sixty percent of total amount of water in Earth. Is the comet alone capable to provide all ocean's water? Or have the comet striked Earth for many times? Without further information about comet, no one could answer the questions above. Perhaps there are other planets serving to provide water other than comet.

Finally, tha author seems to fail to take into account the possibilities that water in oceans of Earth does not come from the so-called striking between different plants at all. Without other credible statistics from scientific research, it is entirely likely that the chemical reaction of oxygen and hydrogen serves to the generation of water.

In sum, as it stands, the argument is not convincing. To better assess the article, the author would better offer more solidary evidence which shows that specific time when comet striked Earth. We also need to know that there is not any other plant but comet striking Earth. It would also be useful to know that the clear process of the water origine. Thus the author's conclusion that the comets provide water all in Earth would be justified.