Mars Was Not Always Bitterly Cold

Scientists at the California Institute of Technology (Caltech) have reported evidence that Mars was warmer and wetter long ago than it is today.  The Caltech scientists say they have directly established the temperature of Mars four billion years ago. At least, they established the surface temperature on part of the planet at that time. The researchers say it is the first such evidence to be discovered and presented.

The Caltech scientists say carbonate（碳酸盐） minerals formed on Mars at about eighteen degrees Celsius. They reached the finding after studying a meteorite（陨石） that had its beginnings near the Martian surface.

Today, the average temperature on Mars is sixty-three degrees below zero Celsius.

The finding was reported on the website of the National Academy of Sciences. Caltech Assistant Professor Woody Fischer helped to prepare the report. He says eighteen degrees Celsius is not especially cold or hot. He says this makes the finding extremely interesting. Knowing the temperature can give scientists an idea of the climate on Mars long ago. It can also help them decide whether the planet had liquid water. Spacecraft orbiting Mars have shown what appear to be rivers, lakebeds and mineral deposits. These pictures suggest that, at one time, water did flow there. Mars Rover vehicles and other spacecraft have confirmed the information.

Caltech Geology Professor John Eiler was another writer of the report. He says knowing the temperature of Mars from long ago provides valuable information. It shows that early in the planet's history, at least part of Mars could support a climate like that of Earth.

The meteorite the scientists examined is one of the oldest known rocks in the world. It is called the Allan Hills meteorite. Its name came from the place in Antarctica where it was found in 1984. The meteorite is believed to have blown loose from the Mars' surface when another space rock struck its "home."

1. The underlined word “establish” in Paragraph 1 probably means “___________”.

2.How did the scientists reach the finding?

3.According to the fourth paragraph, what have spacecraft orbiting Mars done?

4.How did Allan Hills meteorite get its name?

5. Where can we most probably read this passage?

Astronomy (天文学) is the oldest science known to man. Thousands of years ago man looked at the stars and wondered about heavens (天堂). But the six planets that he could see with his eyes alone limited man.

The Greeks studied astronomy over 2,000 years ago. They could see the size, color, and brightness of a star. They could see its place in the sky. They watched the stars move as the seasons changed. But the Greeks had no tools to help themselves study the heavens.

Each new tool added to the field of astronomy helped man reach out into space. Until there were telescopes (望远镜), man did not know much about the moon. He did not know that the planet called Saturn (土星) had rings around it. His sight was so limited that he could not see all the planets. In the early 1700s, people thought there were only six planets. Pluto (冥王星), the last of the nine planets to be discovered was seen until 1930.

Before the spectroscopes (分光镜), man didn’t know what kind of gas was in the sun or other stars, without radio telescopes (射电望远镜), we did not know that radio noise came from far in space.

Today, astronomy is a growing science. We have learned more in the past fifty years than in the whole history of astronomy.

Thousands of years ago, man watched ____ with his eyes.

       A. the moon   B. the stars     C. the universe       D. all the planets

When the Greeks watched the stars, they could ____ .

       A. know what the stars were made of     B. not see their places in the sky

       C. help themselves study the heavens      D. watch the stars move as the seasons changed

Until there were ____ , man knew very little about the moon.

       A. telescopes   B. spectroscopes     C. radio telescopes      D. spaceships

People didn’t know about Pluto until ____ .

       A. the 1700s   B. 2,000 years ago      C. 1930   D. thousands of years ago

____ people began to do research on astronomy.

       A. 50 years ago      B. 90 years ago      C. In the early 1700s    D. Over 2,000 years ago

第三节：完形填空（共20小题，每小题1.5分，满分30分）

   阅读下面短文，掌握其大意，然后从各题所给的四个选项（A、B、C和D）中，选出最佳选项。

The climate will be warm and __21___ with prolonged droughts in most of the world’s grain growing ___22__. Because of the increase in temperature, the ice cap will begin to melt and sea level is predicted to __23___ about ten meters, causing flood in many areas.

  In the atmosphere, a concentration of carbon dioxide acts like the _24__ in the roof of a greenhouse. It allows the sun’s rays to pass _25___ easily on the way to the earth’s _26__, but prevents heat _27__ by the earth from escaping back into space. __28__, as the level of atmospheric carbon dioxide rises,because of the industrial burning of fossil fuels, this greenhouse effect could __29__ the temperature of the earth. The burning of fossil fuels __30__ carbon dioxide. Carbon dioxide accumulates(积聚) in the atmosphere, and __31_ the greenhouse effect, the temperature of the earth’s surface could rise. __32__ this warming up took place, the polar ice caps would begin to melt,__33__raising sea level. The __34__ influence that seems to be cooling the earth is the variable behavior of the sun. As the sun rotates(旋转) on its orbit, it presents hotter or colder faces to the earth, and this seems to have a considerable effect __35__ the distribution of the earth’s atmospheric pressure and on the wind circulation. The heat __36__ of the sun also varied, the latest trend being __37__, the heat output appears to be decreasing and the indications are that the earth’s __38_ is entering a cooler cycle. Scientific models that take __39__ account this __40__ behavior of the sun are also predicting that the world should be entering a new Ice Age. 

21. A. wet            B. rainy                C. dry                  D. icy

22. A. farms                B. regions               C. towns               D. villages

23. A. rise             B. appear                  C. move                D. raise

24. A. glass            B. shylight(天窗)     C. chimney         D. attic(顶楼)

25. A. by              B. over                      C. in                    D. through

26. A. ground        B. bottom                 C. floor               D. surface

27. A. taken in      B. sent out                    C. admitted to      D. taken out

28. A. However     B. Yet                      C. Afterwards        D. Therefore

29. A. benefit               B. forbid                   C. raise              D. effect

30. A. leads to      B. gives off               C. results from      D. joins hands

31. A. as to           B. as for                          C. without          D. because of

32. A. Whether      B. Before                    C. If                    D. After

33. A. so              B. instead                    C. thus              D. but

34. A. natural       B. unusual                C. former                     D. ordinary

35. A. in                      B. on                          C. over                 D. at

36. A. input           B. activity                C. output            D. movement

37. A. downward         B. upward                    C. forward           D. onward

38. A. pressure     B. surface                C. climate          D. appearance

39. A. from          B. into                     C. in                    D. on

40. A. unbelievable B. dull                           C. variable          D. hidden

More and more high-rise buildings have been built in big cities ________ space.

A. in search of        B. in place of      C for lack of          D. in memory of

Humans are responsible for causing changes in the environment that hurt animals and species(物种). We take up more space on Earth for our homes and cities. We pollute habitats(栖息地).    illegally hunt and kill animals. All of these activities take resources and habitats away     plants and animals.

Human activity often changes or destroys the habitats that plants and animals need to survive.     human populations are growing so fast, animals and plants are disappearing many times faster    they have in the past 65 million years.

Animals and plants have always had a     time surviving. Animals became extinct (灭绝的) in the past for a wide variety of reasons. In some cases, competition for resources among animals led to extinction and in     cases, environmental changes caused extinction.

Fortunately, we humans are beginning to realize our mistakes,      we could destroy everything on Earth. We must not only use our knowledge and abilities to manage the Earth, but to make the Earth     safe and healthy place where all animals and plants——including humans ourselves——can live.