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阅读理解
A team of American engineers is studying the feasibility(可行性)of a nuclearpowered mission to the outer edges of the solar system．The target is Neptune, the eighth planet from the sun, and its icy moons．
The answer is a huge spacecraft driven by a compact nuclear reactor．It could drop a series of probes(探测器)into Neptune's atmosphere and help answer questions about the birth of the solar system．
If it gets U．S．National Aeronautics and Space Administration's(NASA)blessing, the Neptune orbiter could be launched around 2016 and arrive in Neptune around 2035．
The project is led by U．S．aircraft manufacturer Boeing and backed by NASA．A twelve－month study of what one scientist calls“the ultimate in deep space exploration”has already begun．
Neptune is a gas giant and sometimes the most distant of the nine planets in the solar system．
It has 11 known moons．The biggest, Triton, is bigger than the sun's ninth planet, Pluto．No spacecraft has been near Neptune since NASA's Voyager 2 sped past it in 1989．
Profound(深奥的)Questions
The Neptune mission is one of 15 competitive for commitment from the U．S．space a gency．Its proposers say the journey could answer profound questions．Because it is one of the most distant members of the sun's planets, Neptune's fabric is more likely to match the original materials of the solar system．
“Neptune is a rawer planet．”said Paul Steffes of the Georgia Institute of Technology．
“It is less influenced by near－sun materials and it is more representative of the original solar system than Jupiter or Saturn．”he added．
Neptune is a puzzle．It is roughly 30 times the distance from the sun as the earth is．It has seasons, and winds whip across its gaseous surface at 1,500 kilometres per hour．
Triton, too, poses riddles．It may not be a natural child of Neptune：It may have been a passing comet from a far－away region called the Kuiper belt captured and imprisoned byNeptune's powerful gravitational field．
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