单选题
What is the topic of the lecture?
【正确答案】
C
【答案解析】[听力原文] 6-11
Let me remind you that ours is not the only planet with a moon. In fact, lots of the other planets in the solar system have one, and some have more than one. Take Mars, for example. The large red planet actually has two, Phobos and Deimos. Now, Phobos is the focus for this lecture. Well, to begin with, it is much closer to Mars than our moon is to us. In fact, of all the moons in the solar system, it's the closest to its planet. And it moves rather quickly as it completes its small orbit. When we talk about planets and moons there is something called the synchronous orbit radius, which is the size and speed of the orbit a moon needs in order to spin around its planet at the same speed as the planet spins around itself. Think of it this way, when a moon reaches synchronous orbit radius, you can stand on the planet's surface and the moon will always stay in the same place in the sky. If a moon is below this orbit, like Phobos is, then it actually rises and sets more than once a day. OK, so we know that Phobos is close to Mars and therefore seems to move quickly across its sky.
I guess the next question that needs to be answered is related to what the moon is made of? Well, we're not really sure, but we have some good guesses. First, most of the material is likely similar to what you would find in a C-type asteroid, which is nothing more than different types of carbon. So, it's like ninety percent carbon. Covering the moon is a one-meter-deep layer of something called regolith. Now, the fact is that it's just a fancy scientific word for a loose layer of material covering rock. A lot of time regolith is just dust or sand, but if it has a lot of organic material in it, we call it soil, just like you would use in a garden.
Phobos is made up of a dust covering and rock underneath, but it is not dense enough to be solid rock to its core. So, it's also likely that the center is made up of ice. In fact, the Russians managed to send a probe to Phobos and observed off gassing, which means that they could detect gases being released from the moon. Unfortunately, the probe stopped working before they could identify the gases, but scientists generally believe that it was water vapor. If you look at these characteristics all together, you can start to see a good argument for the idea that Phobos is just an asteroid that got caught in Martian gravity. I forgot to mention this, but now would be a good time. Phobos is not really that big. It's only 27 km by 21.6 km by 18.8 km. That makes it smaller than Mars's other moon, in fact, smaller than most moons we know of. I wanted to include that because it supports the argument that it's just an asteroid pretending to be a moon. It's not really big enough to be anything else.
We know where it is and what it might be made of. Now let's look to the future. Phobos loses about 1.8 meters of its distance from Mars every one hundred years. Eventually, it's going to hit the planet, right? Well, that's not the case. The moon will fall apart before it gets to the surface. Actually, in about fifty million years, the moon is going to dip down below something called the Roche limit. When that happens, the gravity that holds the moon together will be overcome by the tidal gravity of the planet. The moon will basically fall apart and the smaller pieces will become a planetary ring. Think about the planet Saturn and the rings it has around it. Mars will have the same thing, made up of little bits of Phobos.
So, it's like ninety percent carbon. Covering the moon is a one-meter-deep layer of something called regolith. Now, the fact is that it's just a fancy scientific word for a loose layer of material covering rock. A lot of time regolith is just dust or sand, but if it has a lot of organic material in it, we call it soil, just like you would use in a garden.
Why does the professor say this:
Now, the fact is that it's just a fancy scientific word for a loose layer of material covering rock.
[解析] 主旨题 这是提问讲座要点的问题。教授在讲座一开始就提到太阳系中除了地球以外还有很多行星也有卫星，本课主题是火星的两颗卫星之一的火卫一。选项中因为没有出现火卫一，所以答案是C项。
Let me remind you that ours is not the only planet with a moon. In fact, lots of the other planets in the solar system have one, and some have more than one. Take Mars, for example. The large red planet actually has two, Phobos and Deimos. Now, Phobos is the focus for this lecture. Well, to begin with, it is much closer to Mars than our moon is to us. In fact, of all the moons in the solar system, it's the closest to its planet. And it moves rather quickly as it completes its small orbit. When we talk about planets and moons there is something called the synchronous orbit radius, which is the size and speed of the orbit a moon needs in order to spin around its planet at the same speed as the planet spins around itself. Think of it this way, when a moon reaches synchronous orbit radius, you can stand on the planet's surface and the moon will always stay in the same place in the sky. If a moon is below this orbit, like Phobos is, then it actually rises and sets more than once a day. OK, so we know that Phobos is close to Mars and therefore seems to move quickly across its sky.
I guess the next question that needs to be answered is related to what the moon is made of? Well, we're not really sure, but we have some good guesses. First, most of the material is likely similar to what you would find in a C-type asteroid, which is nothing more than different types of carbon. So, it's like ninety percent carbon. Covering the moon is a one-meter-deep layer of something called regolith. Now, the fact is that it's just a fancy scientific word for a loose layer of material covering rock. A lot of time regolith is just dust or sand, but if it has a lot of organic material in it, we call it soil, just like you would use in a garden.
Phobos is made up of a dust covering and rock underneath, but it is not dense enough to be solid rock to its core. So, it's also likely that the center is made up of ice. In fact, the Russians managed to send a probe to Phobos and observed off gassing, which means that they could detect gases being released from the moon. Unfortunately, the probe stopped working before they could identify the gases, but scientists generally believe that it was water vapor. If you look at these characteristics all together, you can start to see a good argument for the idea that Phobos is just an asteroid that got caught in Martian gravity. I forgot to mention this, but now would be a good time. Phobos is not really that big. It's only 27 km by 21.6 km by 18.8 km. That makes it smaller than Mars's other moon, in fact, smaller than most moons we know of. I wanted to include that because it supports the argument that it's just an asteroid pretending to be a moon. It's not really big enough to be anything else.
We know where it is and what it might be made of. Now let's look to the future. Phobos loses about 1.8 meters of its distance from Mars every one hundred years. Eventually, it's going to hit the planet, right? Well, that's not the case. The moon will fall apart before it gets to the surface. Actually, in about fifty million years, the moon is going to dip down below something called the Roche limit. When that happens, the gravity that holds the moon together will be overcome by the tidal gravity of the planet. The moon will basically fall apart and the smaller pieces will become a planetary ring. Think about the planet Saturn and the rings it has around it. Mars will have the same thing, made up of little bits of Phobos.
So, it's like ninety percent carbon. Covering the moon is a one-meter-deep layer of something called regolith. Now, the fact is that it's just a fancy scientific word for a loose layer of material covering rock. A lot of time regolith is just dust or sand, but if it has a lot of organic material in it, we call it soil, just like you would use in a garden.
Why does the professor say this:
Now, the fact is that it's just a fancy scientific word for a loose layer of material covering rock.
[解析] 主旨题 这是提问讲座要点的问题。教授在讲座一开始就提到太阳系中除了地球以外还有很多行星也有卫星，本课主题是火星的两颗卫星之一的火卫一。选项中因为没有出现火卫一，所以答案是C项。
单选题
According to the professor, why does Phobos rise so often?
【正确答案】
A
【答案解析】[解析] 细节题 教授说，像火卫一这样的卫星如果是在同步轨道上，相对于行星就好像是静止的，如果轨道高度低于同步轨道，一天之中就会不止一次地升起和降落。火卫一的轨道高度低于同步轨道说明和火星表面很近，因此A项是正确答案。
问答题
Is each of these true about the moon Phobos?
For each statement, click in the YES or NO column.
[*]
For each statement, click in the YES or NO column.
[*]
【正确答案】
[*]
[*]
【答案解析】[解析] 内容连接题 本题为新托福听力中的内容连接题(Connecting Content Question)，要求对图表中的概念或者信息进行比较、分类和排列。本题需要考生对火卫一的陈述判断正误。根据讲座内容，火卫一的90%是由碳素组成的，表面大概有1米左右由尘土或沙子组成的风化层，中间部分并不是由岩石组成的。另外，火卫一比火卫二小。
单选题
Which of the following does NOT support the idea that Phobos is just an asteroid?
【正确答案】
C
【答案解析】[解析] 细节题 教授提到火卫一和小行星类似，并列举了几个理由。首先火卫一的大部分由碳组成，这与C型小行星很像，其次中间部分由冰组成的可能性比较大，再次在卫星中属于比较小的。但是没有提到火卫一的形状。
单选题
Why are scientists unsure which types of gases come from Phobos?
【正确答案】
B
【答案解析】[解析] 推理题 第三段提到，俄罗斯曾经发射过探测器探测气体，但是在尚未探明气体成分前探测器就停止了运行。因此，科学家们只是猜测那种气体的成分是水蒸气，但并不确定。所以，选项中最恰当的答案是B项，其他的选项在原文中都没有提到。
单选题
Why does the professor say this:
【正确答案】
C
【答案解析】[解析] 判断意图题 考生需要听讲座的一部分内容，判断教授说其中一句话的意图。教授认为风化层(regolith)是比较陌生的用语，学生们可能会感到比较难，因此C项是正确答案。