泰坦上的湖泊
Liquid Lakes on Saturn's Titan<br />
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<img src="http://i3.tinypic.com/4g8t3x2.jpg" border="0" onclick="zoom(this)" onload="attachimg(this, 'load')" alt="" /><br />
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影像版權: Cassini Radar Mapper, JPL, ESA, NASA <br />
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<font color="navy">Explanation: </font><br />
<font color="dimgray">Why would some regions on Titan reflect very little radar? The leading explanation is that these regions are lakes, possibly composed of liquid methane. The above image is a false-color synthetic radar map of a northern region of Titan taken during a flyby of the cloudy moon by the robotic Cassini spacecraft last July. On this map, which spans about 150 kilometers across, dark regions reflect relatively little of the broadcast radar signal. Images like this show Titan to be only the second body in the Solar System to possess liquids on the surface. Future observations from Cassini during Titan flybys will further test the methane lake hypothesis, as comparative wind effects on the regions are studied. </font><br />
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<font color="navy">說明:</font><br />
<font color="dimgray">為什麼泰坦上有些區域的雷達回波特別少呢？主流的說法是因為那些區域，可能是由液態甲烷所形成的湖泊。這張照片的位置是在泰坦的北部，是去年七月，卡西尼號太空船飛過這顆雲霧滿佈的土星衛星時，用雷達波段所拍攝的假色影像。照片的視野大概是150公里，圖中較暗的區域是比較不易反射雷達波段的地區。這張圖片顯示了泰坦是太陽系中第二顆表面擁有液體的天體。將來，當卡西尼號再次飛越泰坦時，科學家們將更進一步驗證甲烷湖的假設，並比較這些地方的氣流影響。</font><br />
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<font size="2">資料來源: Scientific American<br />
Department of Physics, NCKU</font><font color="white"><font size="1"><br />
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