孙晶楠：托福TPO25阅读篇(原文+翻译)

文/孙晶楠

　　作者简介：新航道北京学校托福阅读主讲，大学英语四、六级写作主讲。 美国Syracuse University交流生，专业英语八级，英语语言文学及人力资源管理双学位，曾担任高校专业英语讲师，并获得高校教师资格证书，专业技术职称，翻译专业资格证书，以及“全国高校中青年骨干教师”称号。对英语学习有独到的见解，擅长在课堂中融入中西方文化知识。理智，风趣。深信“care and diligence bring luck”。

　　ETS发布了TPO25和TPO26，同学询问相关的参考。今天，笔者就针对TPO25阅读为大家作一下翻译，希望广大同学参考译文的准备托福考试。今天请看篇阅读：The Surface of Mars

　　TPO25 READING ONE

　　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.来源：新航道北京学校 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.

　　TPO25 阅读篇文章参考译文：

　　火星表面

　　火星的表面可以看到许多各种不同的地质特征，其中包括太阳系最的巨大火山群和大量的陨石坑。在火星赤道附近的一个庞大地质区--塔尔西斯隆地发现了三座大的火山。塔尔西斯西北部的奥林匹斯火山是迄今为止太阳系中最巨大的火山，高25千米火山底部直径长达700千米。而塔尔西斯隆地的三座大火山要稍微矮一点-----仅有18千米高。

　　这些火山中没有一座火山是由于火星地壳板块撞击的结果而形成的，也就是说火星没有板块运动。反而，它们都是盾形火山—---由熔岩形成并带有辽阔而平缓的坡度。四座火山都显示出与地球上盾形火山一样的与众不同的火山岩浆隧道和其他的流动特征。火星表面图像呈现出许许多多的火山。大多数的大型火山都与特尔西斯隆地有关，但是也有许多小火山是在北部平原被发现的。

　　行星表面微弱的地心引力直接影响了火星上火山的高度。因此，岩浆流动并扩散形成了一座盾形火山，火山最终的高度取决于新山脉形成自身重力的能力。地心引力越弱，重力越小那么山脉的高度就越高。毫无意外的是金星上的麦斯威尔山和地球上夏威夷盾形火山有着同样的高度(大约10千米)超过了它们各自的相同表面地心引力的基数。火星表面地心引力仅为地球表面地心引力的40%，因此火星上的火山高度约为地球火山高度的2.5倍。那么火星上的盾形火山是活动的吗?科学家没有直接证据证明近期或不间断的火山爆发，但是如果这些火山在最近的100,00,0000年(基于火山斜坡上的击坑的范围而得出的一个大概时间)之前就活动着，那么它们中的一些火山可能仍然至少间歇性的活动着。即使火上爆发的间隔在数百万年。

　　火星表面另一个突出的特征就是陨坑。火星宇宙飞船发现在火星及它的两颗卫星表面，都同样点缀着来自太空流星体坠落而形成的陨石坑。同我们的月球一样，较小的火山口通常充满了表层物质---通常是尘埃，火星是一个干燥而荒凉的世界。然而，火星的火山口填充的速度比它的行星月球要的多。在月球，横断面要小于100米(与20米深度一致)的古老的火山口已主要被陨星的腐蚀物所堵塞。在火星，直径小于5千米的古老火山口几乎没有。火星的大气层是一种有效的腐蚀媒介，随着火星上的风将尘埃从一个地方吹到另一个地方并且它清除表面特征要比仅凭借陨星撞击来清除表面特征要快的多。

　　正如在月球上，大陨石坑(如，因为坑口太大，在我们发现它们时还没有被腐蚀物所填充)的范围为火星表面充当了一种年龄指示器。从40亿年的火星南部高地到只有几百万年的最年轻的火山地带，都是通过此种方式评估出年龄的。

　　火星陨石坑复杂的地貌，为行星表层下面的情况提供了一条重要的信息。火星火山口的周边堆积着一些喷出物(是撞击形成的残骸)，看起来与行星月球的不一样。拿月球上的哥白尼火山口与火星上的犹提火山口相对比就证明了其不相同的特征。月球火山口周围的喷出物仅仅是由于火山爆发而喷射出的大量的尘埃，泥土和岩石物质。然而，火星上火山口周围的喷出物却清楚显示出了从火山口喷溅和留出的液状物质。地质学家认为这种液态的火山喷出物显示出在火星表层下仅仅数米就存有极寒冰霜层，或结冰层。爆发性的击加热并融化了冰层，从而导致喷出物出现流动性。

   上面就是托福TPO25阅读篇：The Surface of Mars（火星表面）的原文及翻译，希望考生认真研究TPO真题，陆续我会为大家翻译余下的几篇，敬请关注。

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