- 2018年04月17日17:21 来源：小站整理作者：小站托福编辑
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Now listen to a part of a lecture on the topic you just read about.
Asteroid colonization is not a very practical idea. Each of the points in the reading has a serious downside.
First, while low gravity on an asteroid would make landing and taking off relatively easy, low-gravity environments also present certain risks. In a low-gravity environment, people start losing muscle mass and their bone density becomes lower. Even astronauts who spend just a few months in spaceships, which are low-gravity environments, suffer from health problems like muscle and bone density loss. Imagine the health problems that long-term colonists would experience on asteroids.
Second, the availability of valuable metals might make an asteroid colony seem like a profitable idea but that’s not the whole picture. You have to consider additional factors. One thing is the costs. The costs of supporting a colony and of transporting the metals are likely to be high and will reduce the profits. And furthermore, there’s no guarantee that the price for which you can sell the metals will remain the same. If precious metals are mined in large quantities, it would increase the supply of the metals, which could end up lower in the market price. So mining on asteroids may not be very profitable.
Third, even if some asteroids are easy to reach, they may not be easy to return from. Asteroid orbits, the path on which asteroids travel through space, can be unusual. Some orbital paths come close to earth but then move away from earth, often a great distance away from earth. So even if an asteroid gets close to earth at one point, making it easy for colonists to get to the asteroid, it does not stay close to earth. It can actually travel much farther away from earth than a planet like Mars. Getting back from an asteroid that travels that far would be a challenge.
1 Directions: You have 20 minutes to plan and write your response. Your response will be judged on the basis of the quality of your writing and on how well your response presents the points in the lecture and their relationship to the reading passage. Typically, an effective response will be 150 to 225 words.
Question: Summarize the points made in the lecture, being sure to explain how they challenge the specific points made in the reading passage.
Asteroids are large space objects made of rock and ice. There are hundreds of thousands of asteroids in our solar system. Though we often hear ideas about establishing colonies of humans to live and work on our Moon or our neighboring planet, Mars, some think that sending people to an asteroid would actually be the best colonization option for a number of reasons
To begin with, asteroids are often much smaller than planets, so they have lower gravity. When landing a spaceship, the craft would not be pulled as strongly or as forcefully toward the asteroid's surface, making the landing safer than landing on the Moon or Mars; it would also allow a spacecraft to carry much more equipment needed to set up the colony. It would also be easier for the spacecraft to take off again, so the spaceship would need to carry considerably less fuel for the trip back to Earth.
Mining Valuable Metals
Next some asteroids are rich in valuable elements and precious metals that are relatively rare on Earth, such as gold and platinum. An asteroid colony would be extremely profitable and a good source of these raw materials. The colonists or businesses sponsoring them could more than pay for the cost of their support by mining minerals and sending them back to Earth.
Easy to Reach
Finally, asteroids are a good option for colonization because some of them would be very easy to reach. There are a number of asteroids that periodically come within or near Earth's orbit Some of them actually get closer to Earth than our Moon. So these asteroids would be much easier and more affordable to get to and get back from than a planet like Mars, which would require a two-year trip in each direction.
In the reading, the article comes up with an assumption that sending people to an asteroid would be the best colonization option and lists out three reasons to support this statement. However, in the listening, the professor questions the feasibility of this plan and offers his own perspective on the issue.
First, the reading states that the low-gravity environment on asteroids makes it convenient for people to colonize there. However, in the listening, the professor presents certain risks of low-gravity environments and points out the problem is not that simple. People who live in a low-gravity environment would suffer from muscle loss and lower bone density. Even those astronauts who just spend a short period of time in spaceship would also have muscle and bone density loss, not to mention stay in a low-environment asteroid for longer periods.
Second, the reading claims that the abundant resources on asteroids, such as gold and platinum, would make the prospect of the colonization very profitable and is worth colonizing. However, in the listening, the professor also points out one potential problem in it. The costs of mining and transporting these materials back to earth is would be so high that the profit could be quite minimal. Also, if these raw materials are excavated in large quantities, the price of them is likely to be low in the market because there are too many of them. In this case, the whole business is not lucrative at all.
Third, an easy reach to an asteroid is the third reason why it is worthy of colonization. In the listening, the professor points out one exception which will make the whole issue more complicated than it was expected. Asteroids are easy to reach but not that easy to return from. When an asteroid comes near to the Earth, it is indeed convenient to get onto it. But some orbital path of asteroids are not predictable, they could get quite far away from the Earth. Under this circumstance, getting back from there would be a challenge, or even an illusion.
Therefore, in the listening, the professor asserts that the asteroid colonization is not as simple as it was expected by pointing out three potential problems in the plan.