【资讯】土星最大的卫星：土卫六可能跟地球的咸死海一样

土星最大的卫星：土卫六可能跟地球的咸死海一样

研究人员发现，土卫六的冰壳，它覆盖了非常咸的海洋，在不同绕月球的厚度，暗示地壳正在成为僵化的过程。

图片来源： NASA / JPL / SSI /大学。亚利桑那州/ G的 南特米特里/大学

科学家从美国宇航局的卡西尼任务数据有确凿的证据里面土星最大的卫星，土卫六，海洋可能是因为咸地球的死海。

新的研究结果来自于在过去10年期间，卡西尼号的重复泰坦飞越收集重力和地形数据的研究。使用卡西尼数据，研究人员提出了一个模型结构的泰坦，造成月球的外层冰壳结构的更好的了解。该研究结果发表在杂志伊卡洛斯本周的编辑。

“泰坦继续证明自己作为一个不休迷人的世界，并与我们的长寿命卡西尼号太空船，我们正在解锁新的奥秘一样快，我们解决了旧的，”琳达SPILKER，卡西尼项目科学家在美国宇航局喷气推进实验室（JPL说）在帕萨迪纳，加利福尼亚州，并没有参与这项研究是谁。

其他研究结果支持先前的迹象月球的冰壳是刚性的，在冻结实的过程。研究人员发现，被要求比较高的密度，土卫六的海洋，以解释重力数据。这表明在海洋可能是水极其咸盐水溶解的盐可能由硫，钠和钾的混合。这表明盐水的密度会给海洋中盐的含量大致相等的水是地球上最咸的尸体。

“这是一个非常咸的海洋被地球的标准，说：”该论文的主要作者，南特在法国大学的朱塞佩·米特里。“知道这可能会改变我们看待这个海洋作为一个可能的居留权现今生活的方式，但情况可能有很大的不同有过去。”

卡西尼号的数据还显示土卫六的冰壳的厚度从一个地方略有不同，以地方。研究人员说，如果月球的外壳太硬，因为会出现这种情况，如果海洋中慢慢crystalizing，并把冰这样可以最好地解释。否则，月亮的形状会趋于拉平本身随着时间的推移，像温暖的蜡烛。这个冻结过程将会对土卫六的海洋可居住性具有重要意义，因为这会限制材料的表面和海洋之间交换的能力。

另一种后果刚性冰壳的，根据这项研究，是任何释气甲烷进入土卫六大气层必须发生在分散的“热点” – 就像地球上的热点，导致了夏威夷岛链。土卫六的甲烷不会出现在对流或板块构造回收其冰壳造成的。

如何甲烷进入月球的气氛一直是非常感兴趣的研究人员，因为这种气体分子被阳光短的地质时间尺度上除了打破。土卫六的大气中存在含有约5％的甲烷。这意味着一些过程，认为是地质性质，必须补益中气。研究表明，无论过程负责，泰坦的甲烷的恢复是局部的和间歇性。

“我们的工作表明，寻找甲烷气体释放的迹象，将很难与卡西尼号，并且可能需要未来的使命，可以找到本地化的甲烷来源，”乔纳森Lunine，在康奈尔大学，纽约州伊萨卡的卡西尼任务科学家，并表示一个论文的共同作者。“由于火星上，这是一个具有挑战性的任务。”

卡西尼 – 惠更斯任务是美国宇航局，欧洲航天局和意大利航天局的一个合作项目。喷气推进实验室负责管理美国宇航局科学任务理事会在华盛顿的使命。

有关卡西尼，参观的更多信息

德韦恩布朗

总部，华盛顿

202-354-1726 dwayne.c.brown @ nasa.gov

普雷斯顿Dyches

喷气推进实验室，加利福尼亚州帕萨迪纳

818-354-7013 preston.dyches @ jpl.nasa.gov

下面是全部原文

Scientists analyzing data from NASA’s Cassini mission have firm evidence the ocean inside Saturn’s largest moon, Titan, might be as salty as the Earth’s Dead Sea.

The new results come from a study of gravity and topography data collected during Cassini’s repeated flybys of Titan during the past 10 years. Using the Cassini data, researchers presented a model structure for Titan, resulting in an improved understanding of the structure of the moon’s outer ice shell. The findings are published in this week’s edition of the journal Icarus.

“Titan continues to prove itself as an endlessly fascinating world, and with our long-lived Cassini spacecraft, we’re unlocking new mysteries as fast as we solve old ones,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, who was not involved in the study.

Additional findings support previous indications the moon’s icy shell is rigid and in the process of freezing solid. Researchers found that a relatively high density was required for Titan’s ocean in order to explain the gravity data. This indicates the ocean is probably an extremely salty brine of water mixed with dissolved salts likely composed of sulfur, sodium and potassium. The density indicated for this brine would give the ocean a salt content roughly equal to the saltiest bodies of water on Earth.

“This is an extremely salty ocean by Earth standards,” said the paper’s lead author, Giuseppe Mitri of the University of Nantes in France. “Knowing this may change the way we view this ocean as a possible abode for present-day life, but conditions might have been very different there in the past.”

Cassini data also indicate the thickness of Titan’s ice crust varies slightly from place to place. The researchers said this can best be explained if the moon’s outer shell is stiff, as would be the case if the ocean were slowly crystalizing, and turning to ice. Otherwise, the moon’s shape would tend to even itself out over time, like warm candle wax. This freezing process would have important implications for the habitability of Titan’s ocean, as it would limit the ability of materials to exchange between the surface and the ocean.

A further consequence of a rigid ice shell, according to the study, is any outgassing of methane into Titan’s atmosphere must happen at scattered “hot spots” — like the hot spot on Earth that gave rise to the Hawaiian Island chain. Titan’s methane does not appear to result from convection or plate tectonics recycling its ice shell.

How methane gets into the moon’s atmosphere has long been of great interest to researchers, as molecules of this gas are broken apart by sunlight on short geological timescales. Titan’s present atmosphere contains about five percent methane. This means some process, thought to be geological in nature, must be replenishing the gas. The study indicates that whatever process is responsible, the restoration of Titan’s methane is localized and intermittent.

“Our work suggests looking for signs of methane outgassing will be difficult with Cassini, and may require a future mission that can find localized methane sources,” said Jonathan Lunine, a scientist on the Cassini mission at Cornell University, Ithaca, New York, and one of the paper’s co-authors. “As on Mars, this is a challenging task.”

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA’s Science Mission Directorate in Washington.

For more information about Cassini, visit