In July 1994 Jupiter, the largest planet in our solar system, was struck by 21 pieces of a comet  . When the fragments   landed in the southern part of the giant planet, the explosions were watched by scientists here on earth. But what if our own planet was hit by a comet? The year is 2094. It has been announced that a comet is heading towards the Earth. Most of it will miss our planet, but two fragments will probably hit the southern part of the Earth. The news has caused panic. On 17 July, a fragment four kilometers wide enters the Earth's atmosphere with a huge explosion. About half of the fragment is destroyed. But the major part survives and hits the South Atlantic at 200 times the speed of sound. The sea boils and an enormous wave is created and spreads. The wall of water rushes towards southern Africa at 800 kilometres an hour. Cities on the African coast are totally destroyed and millions of people are drowned. The wave moves into the Indian Ocean and heads towards Asia. Millions of people are already dead in the southern part of the Earth, but the north won't escape for long. Tons of broken pieces are thrown into the atmosphere by the explosions. As the sun is hidden by clouds of dust, temperatures around the world fall to almost zero. Crops are ruined. Wars break out as countries fight for food. A year later civilization has collapsed. No more than 10 million people have survived. Could it really happen? In fact, it has already happened more than once in the history of the Earth. The dinosaurs were on the Earth for over 160 million years. Then 65 million years ago they suddenly disappeared. Many scientists believe that the Earth was hit by a space fragment. The dinosaurs couldn't survive in the cold climate that followed and they became extinct. Will we meet the same end? 57.In writing the passage, the author intends to   _  .
give an accurate description of the possible disaster in the future prove that humans will sooner or later be destroyed warn of a possible disaster in the future tell the historical development of the Earth