水手峽谷: 火星的大峽谷
Valles Marineris: The Grand Canyon of Mars<br />
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<img src="http://i13.tinypic.com/2hp6otk.jpg" border="0" onclick="zoom(this)" onload="attachimg(this, 'load')" alt="" /><br />
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影像提供: Viking Project, USGS, NASA<br />
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<font color="navy">Explanation: </font><br />
The largest canyon in the Solar System cuts a wide swath across the face of Mars. Named Valles Marineris, the grand valley extends over 3,000 kilometers long, spans as much as 600 kilometers across, and delves as much as 8 kilometers deep. By comparison, the Earth's Grand Canyon in Arizona, USA is 800 kilometers long, 30 kilometers across, and 1.8 kilometers deep. The origin of the Valles Marineris remains unknown, although a leading hypothesis holds that it started as a crack billions of years ago as the planet cooled. Recently, several geologic processes have been identified in the canyon. The above mosaic was created from over 100 images of Mars taken by Viking Orbiters in the 1970s. <br />
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<font color="navy">說明: </font><br />
太陽系最大的峽谷將火星的臉畫出一道寬大的割痕。名為水手峽谷的雄偉山谷前後延展了超過3,000公里，最寬處超過600公里寬，而往下約刨了8公里深。相較之下，位於美國亞利桑那州的大峽谷約有800公里長，30公里寬，1.8公里深。儘管有個主要的假說認為，遠在數十億年前行星冷卻時，一道裂縫後來演變成現今的峽谷，水手峽谷真實的成因還無法確定。最近我們已於此峽谷辨識出數種地質演化過程。上面這張馬賽克圖片取材自1970年代海盜號太空船所拍的100多張火星影像。<br />
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<font size="2">資料來源: Scientific American<br />
Department of Physics, NCKU</font>