雅思阅读真题题源文章之venus.pdfVIP

智 课 网 雅 思 备 考 资 料 雅思阅读真题题源文章之Venus 下面是一篇关于水星的雅思阅读真题题源文章，雅思阅读真题题源 是大家练习雅思阅读最好的材料，下面这篇雅思阅读题源文章的主要内 容是关于水星和地球的对比，是一篇偏向于科普类的文章。下面是详细 内容。 Venus and Earth Compared Venus, the second planet from the Sun, lies, on average, 108 million km from the Sun, about 30% closer than the Earth. Venus is often referred to as our sister planet because of similarities in size, mass, density and volume. It is believed that both planets share a common origin forming at the same time out of a condensing nebulosity around 4.5 billion years ago. There the similarities end. Venus has no surface water, a toxic, heavy atmosphere made up almost entirely of carbon dioxide with clouds of sulphuric acid and at the surface the atmospheric pressure is over 90 times that of the Earth at sea-level. The surface of Venus is the hottest in the solar system at a searing 750 K (477 °C). This high temperature has been caused by a catastrophic greenhouse effect due to the carbon dioxide rich atmosphere. Incident sunlight is trapped by the atmosphere and cannot radiate out into space with a resulting boost to the surface temperature by over 475 K. The final anomaly between the two worlds is the rotation of Venus. Firstly its axis of rotation is inclined at 177.36 degrees (compared to 23.5 degrees on Earth). This means that Venus rotates in a retrograde direction from east to west, making the Sun rise in the west and set in the east. Further to this the rotation is very slow: a sidereal day on Venus lasts 243 Earth days. This is even longer than a Venusian year which is only 224.7 Earth days. Despite several missions to Venus there is still much that is unknown about our celestial neighbour. The Russian Venera landers touched down in the 1980s and survived the hostile environment for about 60 minutes during which time images were taken revealing a barren world. Other missions to Venus, both Russian Venera orbiters, and NASAs Magellan spacecraft have concentrated on rada