1 . It took humans thousands of years to understand our own planet, and centuries _______ our neighboring planets. Nowadays, new worlds are being _______ every week.

Up to the present time, astronomers have _______ more than 370 “exoplanets”—planets orbiting (绕……运动) outer space stars (恒星) other than our sun. There is a “hot Saturn (土星)” 260 light-years from Earth that orbits its parent star so _______ that a year there lasts less than three days. _______ another star 150 light-years out is a burning “hot Jupiter (木星),” where upper atmosphere (大气层) is being burning to form a huge comet-like tail. Astronomers have found another three _______ orbiting a pulsar (脉冲星)—the remains of a once huge star shrinking (收缩) into a small atomic nucleus the _______ of a city. Some planets have obviously fallen into their suns. Others have been thrown out of their _______ to become “floaters” that float in the darkness of the universe.

Among all these, scientists are eager to find a clue of the _______: planets like the Earth. That is, planets orbiting their stars at just the right distance—neither too hot nor too cold—to ________ life as we know it. We have not yet found planets that are quite like our own, ________ because they’re inconspicuous (不起眼的). To see a planet as ________ and slim as ours among the brightness of its star is like trying to see a firefly in a fireworks display.   ________ by pushing technology to the ________, astronomers are rapidly approaching the day when they can find another Earth. And when they do, they can examine it for ________ of life.

2 . Bend, a small town in Oregon, is called "moon country". Before the astronauts ever _______ it to the moon, they trained in Bend. When Jim Irwin came to Bend for _______, he made friends with Floyd Watson , a (n) _______ resident , who was the building inspector for the city. Five years later, Irwin was _________ for the Apollo 15 moon landing .

When the news that his old friend would go to the moon came to Watson's_______, he chose a piece of lava rock(火山岩), near Devil's Lake, _______it in paper. Then he posted it to Irwin with a letter where he _______ him and made a request, "I am sending you a _______ piece of Central Oregon lava, which I hope you will be able to_______ to the moon for me . " Off went the letter , and Watson thought ________ of it. A few months later, on July 26, 1971, Irwin________ to the moon with David Scott and Alfred Worden.

And a few weeks after their __________, Watson got an unexpected letter from Irwin. "I did carry your piece of lava to the moon and left it there, "Irwin wrote-and enclosed(附上)a ________ of it, with the small piece of Oregon lava __________with an arrow and the words' Oregon lava on the moon ! " For Watson the letter and the picture were ________. And , of course , he never looked at the moon the same way again.