托福TPO閱讀真題及譯文：The surface of Mars

第一段：

托福TPO閱讀原文：
　　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.

托福TPO閱讀翻譯：
　　火星表面展示了很多種地理特征，包括巨大的火山——太陽系中已知的最大火山——以及覆蓋范圍很廣的隕石坑。在塔爾西斯隆起——火星赤道附近的廣闊地質(zhì)區(qū)域——發(fā)現(xiàn)了三座非常大的火山。位于塔爾西斯西北的奧林帕斯山是其中最大的一座火山：25千米高，測得其基部直徑大約有700千米。位于塔爾西斯隆起的三座大火山則略矮，高度“僅”達18千米。

第二段：

托福TPO閱讀原文：
　　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.

托福TPO閱讀翻譯：
　　這些火山都不是因火星表面的板塊碰撞而形成的——火星上并無板塊運動。這些火山其實是盾狀火山——一種由熔巖形成的斜面寬闊并且坡度平緩的火山。上述4座火山都具有非常明顯的熔巖隧道以及其他流動特征，這與地球上的盾狀火山相似�；鹦潜砻娴膱D像顯示那里存在成百上千的火山。那些最大的火山中的大部分都與塔爾西斯隆起有關(guān)，但是很多稍小的火山都分布在北部平原地區(qū)。

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第三段：

托福TPO閱讀原文：
　　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.

托福TPO閱讀翻譯：
　　火星上火山的可觀的高度是該行星（相對）較低的地表重力導致的直接結(jié)果。當熔巖流淌和蔓延以形成盾狀火山時，這座火山的最終高度取決于這座新生的山承載自身重量的能力。重力越低，重量就越小，山的高度就越高。如金星上的麥克斯韋山與地球上的夏威夷盾狀火山從它們各自的基部算起海拔高度相同（大約10千米高）就不是什么巧合——地球與金星的地表重力相當�；鹦潜砻嬷亓χ挥械厍虻�40%，因此火星上的火山高度大致是地球的2.5倍。火星上的盾狀火山是否還處于活躍期？科學家們沒有直接證據(jù)顯示這些火山近期是否噴發(fā)過，或是否正處于噴發(fā)階段，但是如果這些火山近期的活躍狀態(tài)一如一千萬年前那般（這一最近的爆發(fā)期是根據(jù)火山斜坡上隕石坑的范圍估算出來的），它們當中的幾個也許至少仍然會保持間歇性的活躍。然而，兩次爆發(fā)之間也許間隔數(shù)百萬年之久。

第四段：

托福TPO閱讀原文：
　　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.

托福TPO閱讀翻譯：
　　火星表面的另一個突出特征是隕石坑。水手計劃中的宇宙飛船發(fā)現(xiàn)在火星表面布滿來自太空的流星撞擊表面形成的隕石坑，火星的兩顆衛(wèi)星也是如此。與我們的月球類似，那些較小的隕石坑經(jīng)常被一些物質(zhì)填滿（主要是灰塵），這表明火星是一個干燥的沙漠世界。然而，與月球相比，火星上的隕石坑被填滿的速度明顯要快很多。在月球上，那些直徑不足100米（對應深度大約在20米）的古老隕石坑主要因流星沖擊而形成的塵埃的緣故而被填平了。而在火星上，只有相當少的一部分隕石坑直徑小于5千米�；鹦谴髿馐且环N強效的腐蝕劑，加之火星上的風把灰塵從一個地方卷到另一個地方，較之僅僅是因流星沖擊而形成的塵埃的作用，（火星上的）地表特征被消除得更快。

第五段：

托福TPO閱讀原文：
　　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.

托福TPO閱讀翻譯：
　　與在我們的月球上相同，那些巨大隕石坑的范圍（例如，那些巨大到自形成后尚未被塵埃填滿的隕石坑）充當著火星表面年齡指示器的角色。從火星南部高地的40億年至最年輕的火山地區(qū)的幾千萬年都是用同樣的方法估算的。

第六段：

托福TPO閱讀原文：
　　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.

托福TPO閱讀翻譯：
　　火星表面隕石坑的具體外貌為揭示該行星表面狀況提供了非常重要的信息。火星隕石坑周邊布滿了噴出物（因撞擊而形成的碎片），這與月球上的隕石坑看起來非常不同。對比月球上的哥白尼隕石坑與火星上（相當?shù)湫偷模┯鹊匐E石坑可以看出不同。月球上隕石坑周邊的噴出物正如我們以為的那樣，一場爆炸噴出的大量的灰塵、土壤和巖石。然而，火星（上的隕石坑周邊的）噴出物則因飛濺而出或溢出的液體給人留下了深刻的印象。地質(zhì)學家認為這種具有流體化噴出物的隕石坑指示了在火星地表下幾米處存在永凍土層或水冰。爆炸性的撞擊加熱并液化了這些冰，結(jié)果導致這些噴出物呈現(xiàn)流體狀的特征。