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Discover the cosmos! Each day a differentimage or photograph of our fascinating universe is featured, along with a briefexplanation written by a professional astronomer. Fresh Tiger Stripes on Saturn\'s Enceladus Image Credit: NASA, ESA, JPL, SSI, CassiniImaging Team Explanation: Do underground oceans ventthrough the tiger stripes on Saturn\'s moon Enceladus? Long features dubbedtiger stripes are known to be spewing ice from the moon\'s icy interior intospace, creating a cloud of fine ice particles over the moon\'s South Pole andcreating Saturn\'s mysterious E-ring. Evidence for this has come from the robotCassini spacecraft that orbited Saturn from 2004 to 2017. Pictured here, a highresolution image of Enceladus is shown from a close flyby. The unusual surfacefeatures dubbed tiger stripes are visible in false-color blue. Why Enceladus isactive remains a mystery, as the neighboring moon Mimas,approximately the samesize, appears quite dead. A recent analysis of ejected ice grains has yieldedevidence that complex organic molecules exist inside Enceladus. These largecarbon-rich molecules bolster -- but do not prove -- that oceans underEnceladus\' surface could contain life. 土卫二上的新鲜虎纹 解释：地下的海洋从土卫二上的虎纹中冒出来？这个名为虎纹的长条特征正在从土卫二的内部向外喷射冰，并在土卫二的南极上空产生细小的冰颗粒云，这些冰颗粒云就是土星神秘的E环提的原料。证据来自2004年到2017年绕土星探测的卡西尼号观测数据。这幅图像是卡西尼号近距离飞掠时拍摄到。名为虎纹的异常表面特征用蓝色表示。为什么土卫二如此活跃，这一直都是个谜团，因为它的邻居，大小接近的土卫一却是一片死寂。近日对虎纹喷出的冰颗粒进行分析，证明在土卫二内部存在有复合有机分子。 |
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