选择题：共用题干

共用题干
第一篇

An Expensive Mistake

Is there water on the planet Mars? Is there life on Mars?Was there ever life on Mars?Scientists from
NASA wanted to know the answers to tliese questions.They built a spacecraft to travel around Mars and get
informnation.The spacecraft was called the Mars Climate orbiter.
The Mars Climate Orbiter left for Mars iii December 1998.The trip took nine and a half months.At first,
everything was fine.However.when the Orbiter got near Mars,something terrible happened.The spacecraft
didn't go to the right place.It went too close to Mars.it was too hot for the Orbiter there.The spacecraft
couldn't function correctly.Suddenly,it stopped sending messages to NASA.The Orbiter was lost.
How could this terrible thing happen? How did the Orbiter get closer to Mars than the scientists
planned? Finally,they found the anlswer. Two teams of scientists worked together on the Orbiter. One team
was in England,and one teann was in the United States.There were many similarities in the way they
worked,but there was one important difference:The teams used different guidelines for measuring things.The
United States team used the metric systcnni（公制）.The oilier team used the English system.
Because they used different systems,the scientists made a mathematical mistake.The Orbiter's orbit
(the shape and pattern of its path)around Mars was not correct.The scientists put the Orbiter on the wrong
path.The Orbiter got too close amid too hot,and it stopped functioning.

Why didn'tanybody see the mistake before it was too late?Many things contributed to the problem.
One thing was that NASA scientists and mathematicians were working on two other spacecrafts at the same
time.This was a challenge,and they were very tired from working long hours.
The Mars Climate Orbiter cost $94 million to build.It also cost a lot of money to try to find the lost Or-
biter in space.In addition,NASA's research on the cause of the problem was very expensive.This wasn't
the first time that two different measurement systems caused mistakes in scientific projects.However,the
Mars Climate Orbiter was definitely the most expensive mistake of all!
NASA built the Mars Climate Orbiter to get information about_______.
A:the size of Mars
B:possible life on Mars
C:the shape of Mars
D:the atmosphere of Mars