A question has made the public think a lot for more than a century: Whether(是否) there is life on Mars.

A British spaceship and Europe’s Mars spaceship plan to land on Mars or enter the orbit(轨道) around it. One of the NASA’s spaceships is going to land on January 3, and the other is going to land on the opposite side of Mars on January 24.

Since 1960, over twenty spaceships sent to Mars have failed. Most were lost when they started flying up or landing because those were the most difficult time of any flights.

Scientists wanted to find out whether there was water on Mars. In October, a team of scientists reported that Mars was a dry wasteland(荒地). But weeks later, a second team reported differently that they had found some marks(痕迹). They showed clearly that they were made by the rivers. Such marks told us that Mars was a warmer place billions of years ago—just as life first appeared on Earth. Scientists at once asked the following questions: If it was true, what happened on Mars? Then what about the earth?

Maybe one day, in the near future, human beings will land on Mars, settle on Mars, and directly look for life.

①Most people have a place to call home on Earth. What about in outer space? The International Space Station(ISS) became our first “home” in space in 2000. It welcomed its first crew(队) that year, paving the way(铺平道路) for 20 years of future research.

②“You just have this impression that we’re all citizens(公民) of not a country, but of the planet,” former NASA astronaut Scott Kelly told National Geographic about working in ISS. “We’re all in this thing called humanity(人类) together.”

③Over the past 20 years, the ISS has mainly been used as a science lab, hosting 241 people from 19 countries, according to NASA. They have gone on spacewalks, done research on how space affects the human body, and even grown plants in space.

④ ▲ . For example, the station’s water purification(净化) technology has been used in poor areas to provide clean drinking water. The station also helps to warn us of natural disasters(灾难), such as earthquakes.

⑤However, after being our home in space for over 7,000 days, the station is starting to get old. It has leaked(泄漏) air a few times. Scientists think that the station can keep working until 2024. After that, scientists will bring it down to Earth. It is believed that Earth’s atmosphere(大气) will burn up most of the station. Other debris(残骸) will fall into the Pacific Ocean.

⑥In the future, space will be home to more stations like the ISS. NASA is building a space station that is smaller than the ISS near the moon. Also, China will have its own space station up in 2022.

(a. gone on spacewalks        b. provide clean water for poor areas       c. stopped earthquakes       

d. learned how space affects the human body            e. grown plants )