托福阅读真题+题目+答案：Interplanetary Seeding

托福阅读真题+题目+答案：Interplanetary Seeding

Some scientists believe that microbial life may be distributed across terrestrial planets by interplanetary rocks. Rocks are capable of carrying microbes from the surface of one planet, across hundreds of millions of miles of space, to neighboring planets. Each year, Earth is impacted by half a dozen half-kilogram or larger rocks from Mars. These rocks were blasted off Mars by large impacts and found their way to orbits that cross Earth's path, where they eventually collided with Earth as meteorites. Nearly 10 percent of the rocks blasted into space from Mars end up on Earth. All planets are impacted by interplanetary objects large and small over their entire lifetimes, and the larger impacts actually eject rocks into space and into orbit about the Sun.

1.Which of the following can be inferred from paragraph 1 about rocks that are blasted off Mars by large impacts?

A Their number is smaller than the number of rocks that are blasted off Earth.

B Nearly 10 percent of them are capable of carrying microbes.

C Half of them collide with Earth as meteorites.

D Some of them may orbit the Sun.

A glance at the full Moon with binoculars shows long streaks, or rays, radiating from the crater Tycho, located near the bottom of the Moon as seen by observers in the Northern Hemisphere. The rays are produced by the fallback of impact debris (impact material)ejected from the crater, which is 100 kilometers in diameter. The rays can be traced nearly across the full observable side of the Moon. and such long "airborne" flight is evidence that some ejecta (ejected materials) were accelerated to near-orbital speed. Debris ejected to speeds higher than the escape speed(2.2 kilometers per second)did not fall back but flew into space It has long been appreciated that material could be ejected from the Moon by impacts, but only in the relatively recent past have we realized that whole rocks greater than10 kilograms in mass could be ejected from terrestrial planets and not be severely modified by the process It was formerly believed that the launch process would shock-melt or at least severely heat the ejected material. There was little expectation that rocks capable of carrying living microbes from planet to planet would survive the great violence of the launch. The discovery of lunar(Moon)rocks in Antarctica showed that this is possible.

2.According to paragraph 2, which of the is NOT true of the crater Tycho?

A It stretches one hundred kilometers across the surface of the Moon.

B All of the debris from the impact that created it fell back to the surface of the Moon.

C Debris stretches out from it like rays, reaching great distances.

D It is near the bottom of the Moon as seen from the Northern Hemisphere.

3.According to paragraph 2, for rocks on the Moon to be ejected into space, which of the following would have to be true?

A The rocks would have to be greater than 10 kilograms in mass.

B The Moon would have to be hit by a meteorite at least 100kilometers in diameter.

C The meteorite would have to hit in a particular region of the Moon's surface.

D The rocks would have to travel faster than 2.2 kilometers per second

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