A NASA spacecraft flew by Pluto, sending to scientists a message that it survived its historic encounter before sending back the closest look ever of the distant planet.

After a three-billion-mile journey, the nuclear-powered New Horizons -- about the size of a piano -- took pictures of Pluto. The photos will show details of Pluto never seen before in the history of space travel. The images are to be shown by the US space agency on Wednesday.

New Horizons is moving faster than any spacecraft ever built, at a speed of about 30,800 miles per hour. Some 13 hours after the flyby, applause broke out in mission control at the Johns Hopkins Applied Physics Center outside the US capital Washington. "We have a healthy spacecraft," said mission operations manager Alice Bowman. The confirmation eased anxiety among scientists who were waiting all day to find out if the $700 million New Horizons survived the Kuiper Belt, the region beyond Neptune that Stern has described as a "shooting gallery" of cosmic debris. NASA had said there was a one in 10,000 chance that the spacecraft could be lost, and all it would take would be "a collision with a particle as small as a grain of rice".

"It is truly amazing that humankind can go out and explore these worlds. And to see Pluto be revealed just before our eyes -- it is just fantastic," Bowman said. Obama cheered the mission on Twitter. "Pluto just had its first visitor! Thanks @NASA - it's a great day for discovery and American leadership," the US president wrote.

The spacecraft launched in 2006. New Horizons is the first spacecraft to fly past Pluto and its seven scientific instruments aim to explore details of the surface, geology and atmosphere of Pluto and its five moons.

Already, scientists have learned from New Horizons that Pluto is 12-18 miles larger than previously thought, with a radius of 736 miles. Scientists have also confirmed the existence of a polar ice cap on Pluto and found nitrogen escaping from Pluto’s atmosphere.

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1.Why are the photos from New Horizons important?

A Because New Horizons has traveled three-billion-mile.

B Because they show the details of Pluto for the first time.

C Because they will be shown by the US space agency soon.

D Because it took more than $700 million to take the photos.

解析：选B。B。细节理解题。根据文章第2段第2句的The photos will show details of Pluto never seen before in the history of space travel可知这是在历史上第一次拍摄到冥王星的这么清晰细节的照片。

2.What made people in mission control feel anxious?

A New Horizons’ faster speed.

B New Horizons’ possible collision.

C New Horizons’ becoming bigger.

D New Horizons’ shooting gallery.

解析：选B。B。推理判断题。根据第3段最后一句的...all it would take would be "a collision with a particle as small as a grain of rice.可知该新视野号面对的潜在危险是碰撞。

3.What Obama wrote means ______.

A Pluto should have more visitors

B Pluto will be discovered soon

C American can have leadership

D it’s great to get Pluto’s photos

解析：选D。D。推理判断题。根据第4段第4、5句的Pluto just had its first visitor! Thanks @NASA - it's a great day for discovery可知Obama总统为新拍摄的照片而赞美。

4.How long has new Horizons been traveling?

A 13 hours.

B 10,000 hours.

C 6 years.

D 10 years.

解析：选D。D。细节理解题。根据文章第5段第1句的The spacecraft launched in 2006.可知该航天器是在2006年被发射上去的，因此在太空中飞翔了10年了。

5.What have the scientists learned about Pluto?

A There is some kind of ice cap on Pluto.

B There is oxygen in Pluto’s atmosphere.

C Pluto is soon becoming larger and larger.

D Pluto is a good place to build space station.

解析：选A。A。细节理解题。根据文章最后一段第2句的Scientists have also confirmed the existence of a polar ice cap on Pluto.可以得知通过新视野号科学家们已经确认的冰盖的存在。