『新东方在线托福阅读』为托福考生准备了ETS托福TPO/Official 25 Passage 1阅读练习：In paragraph 4, why does the author point out that Mars has few ancient craters that are less than 5 kilometers in diameter?真题题目及答案解析，TPO/Official 25 Passage 1阅读原文范文音频翻译

托福TPO/Official 25 Passage 1阅读原文In paragraph 4, why does the author point out that Mars has few ancient craters that are less than 5 kilometers in diameter?题目答案及解析-新东方托福官方网校手机版

火星表面展示出广泛的地质特征，包括巨大的火山——太阳系中已知的最大的火山——和大量的撞击坑。

The surface of Mars shows a wide range of geologic features, including huge volcanoes-the largest known in the solar system-and extensive impact cratering.

在塔尔西斯凸起上发现了三座非常大的火山，塔尔西斯凸起是火星赤道附近的一个巨大的地质区域。

Three very large volcanoes are found on the Tharsis bulge, an enormous geologic area near Mars’s equator.

塔尔西斯的西北部是最大的火山:奥林匹斯山，高25公里，底部直径约700公里。

Northwest of Tharsis is the largest volcano of all: Olympus Mons, with a height of 25 kilometers and measuring some 700 kilometers in diameter at its base.

塔尔西斯凸起的三座大火山稍小一些——“仅仅”18公里高。

The three large volcanoes on the Tharsis bulge are a little smaller-a “mere” 18 kilometers high.

这些火山没有一个是由于火星地壳板块之间的碰撞而形成的——火星上没有板块运动。

None of these volcanoes was formed as a result of collisions between plates of the Martian crust-there is no plate motion on Mars.

相反，它们是盾状火山——由熔岩形成的斜面宽阔并且坡度平缓的火山。

Instead, they are shield volcanoes — volcanoes with broad, sloping slides formed by molten rock.

这四个地方都有独特的熔岩通道和其他类似地球上盾状火山的流动特征。

All four show distinctive lava channels and other flow features similar to those found on shield volcanoes on Earth.

火星表面的图像显示有数百座火山。

Images of the Martian surface reveal many hundreds of volcanoes.

最大火山中的大部分都与塔尔西斯凸起有关，但在北部平原上发现了许多较小的火山。

Most of the largest volcanoes are associated with the Tharsis bulge, but many smaller ones are found in the northern plains.

火星火山的巨大高度是该星球表面低重力的直接结果。

The great height of Martian volcanoes is a direct consequence of the planet’s low surface gravity.

随着熔岩的流动和扩散形成盾状火山，这座火山的最终高度取决于这座新火山支撑自身重量的能力。

As lava flows and spreads to form a shield volcano, the volcano’s eventual height depends on the new mountain’s ability to support its own weight.

重力越低，重量越轻，山的高度就越高。

The lower the gravity, the lesser the weight and the greater the height of the mountain.

金星上的麦克斯韦尔蒙斯火山和地球上的夏威夷盾状火山在各自的基础上上升到大约相同的高度（约10公里）并非偶然——地球和金星有着相似的表面引力。

It is no accident that Maxwell Mons on Venus and the Hawaiian shield volcanoes on Earth rise to about the same height (about 10 kilometers) above their respective bases-Earth and Venus have similar surface gravity.

火星表面的重力只有地球的40%，所以火山的高度大约是地球的2.5倍。

Mars’s surface gravity is only 40 percent that of Earth, so volcanoes rise roughly2.5 times as high.

火星盾状火山还在活动吗？科学家们没有直接证据证明最近或正在发生的火山喷发，但如果这些火山的活跃状态一如一亿年前（最后一次火山喷发的时间是根据火山斜坡上的撞击坑的大小来估计的），一些火山可能仍然至少间歇地活跃。

Are the Martian shield volcanoes still active? Scientists have no direct evidence for recent or ongoing eruptions, but if these volcanoes were active as recently as 100 million years ago (an estimate of the time of last eruption based on the extent of impact cratering on their slopes), some of them may still be at least intermittently active.

然而，在两次喷发之间可能会有数百万年的时间。

Millions of years, though, may pass between eruptions.

火星表面的另一个显著特征是陨石坑。

Another prominent feature of Mars’s surface is cratering.

水手号宇宙飞船发现火星表面和它的两个卫星表面都布满了陨石坑，这些陨石坑是由从太空坠落的流星体形成的。

The Mariner spacecraft found that the surface of Mars, as well as that of its two moons, is pitted with impact craters formed by meteoroids falling in from space.

就像在我们的月球上一样，较小的陨石坑往往充满了表面物质——大部分是灰尘——这证实了火星是一个干燥的沙漠世界。

As on our Moon, the smaller craters are often filled with surface matter-mostly dust-confirming that Mars is a dry desert world.

然而，火星上的陨石坑比月球上的要快得多。

However, Martian craters get filled in considerably faster than their lunar counterparts.

在月球上，直径不到100米（相当于深度约20米）的古代陨石坑已经消失，这主要是由于陨石的侵蚀。

On the Moon, ancient craters less than 100 meters across (corresponding to depths of about 20 meters) have been obliterated, primarily by meteoritic erosion.

在火星上，直径小于5公里的陨石坑相对较少。

On Mars, there are relatively few craters less than 5 kilometers in diameter.

火星大气是一种有效的侵蚀介质，火星风把灰尘从一个地方吹到另一个地方，擦除地表特征的速度远远快于流星的撞击。

The Martian atmosphere is an efficient erosive agent, with Martian winds transporting dust from place to place and erasing surface features much faster than meteoritic impacts alone can obliterate them.

就像在月球上一样，巨大的撞击坑的大小（也就是说，

As on the Moon, the extent of large impact cratering (i.e.

自形成以来，由于侵蚀作用而无法填补的坑）是火星表面年龄的标志。

craters too big to have been filled in by erosion since they were formed) serves as an age indicator for the Martian surface.

通过这种方法，科学家们获得了从40亿年的火星南部高地到几亿年的最年轻火山地区的估算年龄。

Age estimates ranging from four billion years for Mars’s southern highlands to a few hundred million years in the youngest volcanic areas were obtained in this way.

火星陨石坑的详细外观提供了关于火星表面以下条件的重要信息。

The detailed appearance of Martian impact craters provides an important piece of information about conditions just below the planet’s surface.

火星上的陨石坑被喷出物（撞击形成的碎片）所包围，这与月球上的陨石坑截然不同。

Martian craters are surrounded by ejecta (debris formed as a result of an impact) that looks quite different from its lunar counterparts.

将月球上的哥白尼陨石坑与火星上（相当典型的）尤蒂陨石坑进行比较，就可以看出区别。

A comparison of the Copernicus crater on the Moon with the (fairly typical) crater Yuty on Mars demonstrates the differences.

围绕在月球陨石坑周围的喷出物，和人们所能预料到的喷出大量灰尘、土壤和岩石的物质的大爆炸一致。

The ejecta surrounding the lunar crater is just what one would expect from an explosion ejecting a large volume of dust, soil, and boulders.

然而，火星上的喷出物给人一种清楚的印象，那就是有液体溅出或流出陨石坑。

However, the ejecta on Mars gives the distinct impression of a liquid that has splashed or flowed out of crater.

地质学家认为，这个流态化的喷出火山口表明，地表下几米深处有一层永久冻土层，即水冰。

Geologists think that this fluidized ejecta crater indicates that a layer of permafrost, or water ice, lies just a few meters under the surface.

爆炸性的撞击使冰加热和液化，导致喷出物的流体外观。

Explosive impacts heated and liquefied the ice, resulting in the fluid appearance of the ejecta.

According to paragraph 1, Olympus Mons differs from volcanoes on the Tharsis bulge in that Olympus Mons

According to paragraphs 1 and 2, which of the following is NOT true of the shield volcanoes on the Tharsis bulge?

In paragraph 3, why does the author compare Maxwell Mons on Venus to the Hawaiian shield volcanoes on Earth?

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

According to paragraph 4, what is demonstrated by the fact that craters fill in much faster on Mars than on the Moon?

In paragraph 4, why does the author point out that Mars has few ancient craters that are less than 5 kilometers in diameter?

According to paragraph 5, what have scientists been able to determine from studies of large impact cratering on Mars?

According to paragraph 6, the ejecta of Mars's crater Yuty differs from the ejecta of the Moon's Copernicus crater in that the ejecta of the Yuty crater

Look at the four squares  that indicate where the following sentence could be added to the passage. This surface feature has led to speculation about what may lie under Mars's surface.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.

Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selected THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

The Surface of Mars The surface of Mars shows a wide range of geologic features, including huge volcanoes-the largest known in the solar system-and extensive impact cratering. Three very large volcanoes are found on the Tharsis bulge, an enormous geologic area near Mars's equator. Northwest of Tharsis is the largest volcano of all: Olympus Mons, with a height of 25 kilometers and measuring some 700 kilometers in diameter at its base. The three large volcanoes on the Tharsis bulge are a little smaller-a "mere" 18 kilometers high. None of these volcanoes was formed as a result of collisions between plates of the Martian crust-there is no plate motion on Mars. Instead, they are shield volcanoes — volcanoes with broad, sloping slides formed by molten rock. All four show distinctive lava channels and other flow features similar to those found on shield volcanoes on Earth. Images of the Martian surface reveal many hundreds of volcanoes. Most of the largest volcanoes are associated with the Tharsis bulge, but many smaller ones are found in the northern plains. The great height of Martian volcanoes is a direct consequence of the planet's low surface gravity. As lava flows and spreads to form a shield volcano, the volcano's eventual height depends on the new mountain's ability to support its own weight. The lower the gravity, the lesser the weight and the greater the height of the mountain. It is no accident that Maxwell Mons on Venus and the Hawaiian shield volcanoes on Earth rise to about the same height (about 10 kilometers) above their respective bases-Earth and Venus have similar surface gravity. Mars's surface gravity is only 40 percent that of Earth, so volcanoes rise roughly 2.5 times as high. Are the Martian shield volcanoes still active? Scientists have no direct evidence for recent or ongoing eruptions, but if these volcanoes were active as recently as 100 million years ago (an estimate of the time of last eruption based on the extent of impact cratering on their slopes), some of them may still be at least intermittently active. Millions of years, though, may pass between eruptions. Another prominent feature of Mars's surface is cratering. The Mariner spacecraft found that the surface of Mars, as well as that of its two moons, is pitted with impact craters formed by meteoroids falling in from space. As on our Moon, the smaller craters are often filled with surface matter-mostly dust-confirming that Mars is a dry desert world. However, Martian craters get filled in considerably faster than their lunar counterparts. On the Moon, ancient craters less than 100 meters across (corresponding to depths of about 20 meters) have been obliterated, primarily by meteoritic erosion. On Mars, there are relatively few craters less than 5 kilometers in diameter. The Martian atmosphere is an efficient erosive agent, with Martian winds transporting dust from place to place and erasing surface features much faster than meteoritic impacts alone can obliterate them. As on the Moon, the extent of large impact cratering (i.e. craters too big to have been filled in by erosion since they were formed) serves as an age indicator for the Martian surface. Age estimates ranging from four billion years for Mars's southern highlands to a few hundred million years in the youngest volcanic areas were obtained in this way. The detailed appearance of Martian impact craters provides an important piece of information about conditions just below the planet's surface. Martian craters are surrounded by ejecta (debris formed as a result of an impact) that looks quite different from its lunar counterparts. A comparison of the Copernicus crater on the Moon with the (fairly typical) crater Yuty on Mars demonstrates the differences. The ejecta surrounding the lunar crater is just what one would expect from an explosion ejecting a large volume of dust, soil, and boulders.  However, the ejecta on Mars gives the distinct impression of a liquid that has splashed or flowed out of crater.  Geologists think that this fluidized ejecta crater indicates that a layer of permafrost, or water ice, lies just a few meters under the surface.  Explosive impacts heated and liquefied the ice, resulting in the fluid appearance of the ejecta.