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旁白：请听一段天文学的课堂讲解。

Narrator: Listen to part of a lecture in an astronomy class.

教授：几个世纪来许多人都对厚云层覆盖的金星有着深厚的兴趣，它被称之为神秘的星球。

Professor: Many people have been fascinated about Venus for centuries because of its thick cloud cover, this so-called planet of mystery and all of that.

关于金星地表的一些问题还没有被解决，但是在过去的几年中我们也对之有所了解。

Some questions about the surface are still unresolved but, but we have learned a lot about it in the past several years.

首先，让我说一下我们已经能够穿过这些厚厚的云层。

First of all, let me talk about how we have been able to get past those clouds.

首先，是苏联的“金星二号”探测器，它直接着陆在金星表面并发回了它周围的图像。

First, there were Soviet modules that landed directly on the surface and sent back some images of what was around them.

其次，我们用金星上空的卫星进行了雷达成像。

Second, we did some radar imaging from satellites from above.

学生：嗯，我记得读到过，并没有多大的收获，金星的地表的大部分地区十分平坦。

Student: Well, I remember reading that there's not really a lot going on, that the surface of Venus is just flat and smooth in a lot of places.

教授：嗯……是的，大部分地区十分平坦。

Professor: Um...Yeah, It's smooth in a lot of places.

但是并不是，嗯……并不全是这样。

But that's not, um... that's not the whole picture.

在其它地区，有火山、轮廓清晰的山谷、陨石坑、熔岩穹丘，这些熔岩的形状就像是巨大的薄饼。

In other areas, you've got canyons, ripped valleys, meteor craters, uh, lava domes, these lava formations that look like giant pancakes.

金星地表最有意思的特征是火山的地盾。

Well, one of the most interesting features on the surface are in fact the shield volcanoes.

地盾是由于岩浆反复从一个地方喷出地表而形成的。

Shield volcanoes formed when magma comes out of the ground in the same spot over and over again.

记住，岩浆是地下热的熔化了的岩石，当流出地表后就称为岩浆。

Remember, magma is hot molten rock that's underground, and it is called lava when it reaches the surface.

这样，岩浆构成并冷却成火山。

Uh, so the lava builds up, and hardens, and a volcano forms.

So shield volcanoes have very gentle sloping sides.

它们被叫做盾状火山，是因为从上空看起来它们的形状比较像盾，就是战士的盾牌。

They are called shield volcanoes, because viewed from above, they kind of resemble shields, you know, like a warrior's shield.

十分有趣的是地球上的火上大部分都不是盾状火山。

But what's particularly interesting about these volcanoes is that most of the volcanoes here on Earth are not shield volcanoes.

相反的，是其它种类的火山，例如，地层火山，是地球板块运动造成的。

Instead, they are other volcano types, like strata volcanoes, for example, which are a result of tectonic plate movement.

在地壳下方，有许多缓缓移动的板块。

Underneath the Earth's crust, there are a number of shifting slabs or plates that are slowly moving.

而在不同板块连接或互相作用的地区，存在着地球上大部分的火山。

And in the zones on the edges of the plates where different plates meet and interact, that's where we get most of Earth's volcanoes.

而在金星上，火山并不像在地球上一样在个别地区集中。

On Venus, however, volcanoes are not clustered in discrete zones like they are on Earth.

相反地它们很随机的分布在金星的表面。

Instead, they are more or less randomly scattered over Venus's surface.

金星上大部分是盾状火山，它们的分布十分分散，这说明金星没有移动的地质板块，这与地球十分的不同。

Venus has mostly shield volcanoes, and they are randomly scattered, that indicates that Venus does not have moving tectonic plates, and that's a big difference compared to Earth.

在地球上，活动的地质板块是只要的地质因素，对整个地表的动态变化十分的重要，对不对？

Here on Earth, moving tectonic plates are a major geological element, just crucial for the whole surface dynamic, right?

嗯……其中一个是说由于火星没有地表水，地表水可以为地质板块的运动起到润滑作用，就像在地球上一样。

Um...One of them is that this has to do with the fact that Venus has no surface water that's needed to kind of lubricate the movement of the plates, you know, like oceans on Earth.

Did you say we have shield volcanoes on Earth?

教授：当然可以了。在太平洋的夏威夷岛上的火山就是盾状火山。

Professor: Sure. The volcanoes in the Hawaii islands, in the Pacific Ocean are shield volcanoes.

它们是由地下喷出的岩浆构成的。

They are formed over a hot spot of magma.

所以在地球上的火山有很多种，而金星上的火山却差不多只有一种。

So while on Earth we have several types of volcanoes, on Venus there's mostly the one type.

学生：金星上的火山是活火山吗？

Student: Are the volcanoes on Venus still active?

教授：嗯，这个问题很有意思。

Professor: Well, that's an interesting question.

There is still some discussion on that point.

首先，金星云层中的二氧化硫的含量显示出很大幅度并经常的波动。

First, the level of sulfur dioxide gas above Venus's clouds shows large and very frequent fluctuations.

这些波动有可能是由二氧化硫不断地骤增和骤减引起的。

It is quite possible that these fluctuations, the huge increase and decrease of sulfur dioxide, happening again and again.

很有可能这是由火山爆发引起的，因为火山爆发常常会发射出气体。

It's quite possible that this is due to volcanic eruptions, because volcanic eruptions often emit gases.

如果是这样的话，火山活动很有可能是造成金星厚云盖的根本原因。

If that's the case, volcanism could very well be the root cause of Venus's thick cloud cover.

而且我们观察到金星表面会爆发出电磁能量。

And also we have observed bursts of radio energy from the planet's surface.

这种爆发与我们在地球上看到的火山爆发相似。

These bursts are similar to what we see when volcanoes erupt on Earth.

这也同样使人联想到火山活动。

So this too suggests ongoing volcanic activity.

但尽管这个证据十分有吸引力，但是到目前为止并没有人真正的见过金星的火山爆发，所以我们无法肯定。

But although this is intriguing evidence, no one's actually observed a Venus volcano erupting yet, so we can't be positive.

How were scientists able to learn new information about Venus' surface?

What differences between volcanoes on Venus and those on Earth does the professor mention?

Why does the professor mention the fact that Venus has no surface water?

According to the professor, what is a possible origin of Venus' clouds?

What is the professor's opinion about the theory that Venus' volcanoes are active?

Narrator: Listen to part of a lecture in an astronomy class. 
Professor: Many people have been fascinated about Venus for centuries because of its thick cloud cover, this so-called planet of mystery and all of that. Well, what's under those clouds? What's the surface of the planet like? Some questions about the surface are still unresolved but, but we have learned a lot about it in the past several years. 
First of all, let me talk about how we have been able to get past those clouds. First, there were Soviet module that landed directly on the surface and sent back some images of what was around them. Second, we did some radar imaging from satellites from above. Radar can get through the clouds. So what have we learned? Yes, Karen? 
Student: Well, I remember reading that there's not really a lot going on, that the surface of Venus is just flat and smooth in a lot of places. 
Professor: Yeah, smooth in a lot of places. But that's not, um... that's not the whole picture. In other areas, you've got canyons, ripped valleys, meteo craters, uh, lava domes, these lava formations that look like giant pancakes. And also volcanoes. 
Well, one of the most interesting features on the surface are in fact the shield volcanoes. Shield volcanoes formed when magma comes out of the ground in the same spot over and over again. Remember, magma is hot molten rock that's underground, and it is called lava when it reaches the surface. Uh, so the lava builds up, and hardens, and a volcano forms. 
Now, the lava on Venus is thin. It spreads out easily. So shield volcanoes have very gentle sloping sides. They are called shield volcanoes, because viewed from above, they kind of resemble shields, you know, like a warrior's shield. 
But what's particularly interesting about these volcanoes is that most of the volcanoes here on Earth are not shield volcanoes. Instead, they are other volcano types, like strata volcanoes, for example, which are a result of tectonic plate movement. Remember tectonic plates? 
Underneath the Earth's crust, there are a number of shifting slabs or plates that are slowly moving. And in the zones on the edges of the plates where different plates meet and interact, that's where we get most of Earth's volcanoes. On Venus, however, volcanoes are not clustered in discrete zones like they are on Earth. Instead, they are more or less randomly scattered over Venus's surface. Well, that's significant. Venus has mostly shield volcanoes, and they are randomly scattered, that indicates that Venus does not have moving tectonic plates, and that's a big difference compared to Earth. Here on Earth, moving tectonic plates are a major geological element, just crucial for the whole surface dynamic, right? 
So why doesn't Venus have them? Well, there are a few theories. One of them is that this has to do with the fact that Venus has no surface water that's needed to kind of lubricate the movement of the plates, you know, like oceans on Earth. 
Yeah, I forgot to spell that out. Uh, Venus has no surface water. 
Student: Wait a second. Did you say we have shield volcanoes on Earth? Can you give an example? 
Professor: Sure. The volcanoes in the Hawaii islands, in the Pacific Ocean are shield volcanoes. They are formed over a hot spot of magma. So while on Earth we have several types of volcanoes, on Venus there's mostly the one type. Uh, Eric? 
Student: Are the volcanoes on Venus still active? 
Professor: Well, that's an interesting question. There is still some discussion on that point. But here's what we do now. First, the level of sulfur dioxide gas above Venus's clouds shows large and very frequent fluctuations. It is quite possible that these fluctuations, the huge increase and decrease of sulfur dioxide, happening again and again. It's quite possible that this is due to volcanic eruptions, because volcanic eruptions often emit gases. If that's the case, volcanism could very well be the root cause of Venus's thick cloud cover. And also we have observed bursts of radio energy from the planet's surface. These bursts are similar to what we see when volcanoes erupt on Earth. So this too suggests ongoing volcanic activity. But although this is intriguing evidence, no one's actually observed a Venus volcano erupting yet, so we can't be positive. 
Professor: Well, that's an interesting question. There is still some discussion on that point. But here's what we do now. First, the level of sulfur dioxide gas above Venus's clouds shows large and very frequent fluctuations. It is quite possible that these fluctuations, the huge increase and decrease of sulfur dioxide, happening again and again. It's quite possible that this is due to volcanic eruptions, because volcanic eruptions often emit gases. If that's the case, volcanism could very well be the root cause of Venus's thick cloud cover. And also we have observed bursts of radio energy from the planet's surface. These bursts are similar to what we see when volcanoes erupt on Earth. So this too suggests ongoing volcanic activity. But although this is intriguing evidence, no one's actually observed a Venus volcano erupting yet, so we can't be positive.