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Replacement and late formation of atmospheric N2 on undifferentiated Titan by impacts

唐唐添加于 2011-5-27 04:21 | 1735 次阅读 | 0 个评论

作者
Sekine Y, Genda H, Sugita S, Kadono T, Matsui T
摘要
Saturn’s moon Titan has attracted much attention because of its massive nitrogen atmosphere1, but the origin of this atmosphere is largely unknown. Massive secondary atmospheres on planets and satellites usually form only after a substantial differentiation of the body’s interior and chemical reactions during accretion2, 3, 4, 5, 6, 7, yet Titan’s interior has been found to be incompletely differentiated8. Here we propose that Titan’s nitrogen atmosphere formed after accretion, by the conversion from ammonia that was already present on Titan during the period of late heavy bombardment about four billion years ago9. Our laser-gun experiments show that ammonia ice converts to N2 very efficiently during impacts. Numerical calculations based on our experimental results indicate that Titan would acquire sufficient N2 to sustain the current atmosphere and that most of the atmosphere present before the late heavy bombardment would have been replaced by impact-induced N2. Our scenario is capable of generating a N2-rich atmosphere with little primordial Ar on undifferentiated Titan. If this mechanism generated Titan’s atmosphere, its N2 was derived from a source in the solar nebula different from that for Earth, and the origins of N2 on Titan and Triton may be fundamentally different from the origin of N2 on Pluto.
详细资料
- 文献种类:期刊
- 期刊名称: Nature Geoscience
- 期刊缩写: Nature Geosci
- 期卷页: 2011年
- ISBN: 1752-0894
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土卫泰坦氮云层由行星碰撞产生

土星的卫星泰坦被一层厚厚的氮云层所笼罩，这些氮云是怎么形成的呢？研究人员认为，大约在 40多亿年前发生的晚期重度轰炸中，行星间的碰撞导致氨冰转化为氮气，新成果发表在5月在线出版的《自然—地球科学》期刊上，有可能会解释在这个相对寒冷的星球上为什么会形成一层厚厚的云。

利用激光枪实验，Yasuhito Sekine分析了一种正确的观点：行星碰撞导致氨冰转化为气体氮，从而形成了泰坦上的氮云层。他们发现，泰坦可以通过这种方式产生足够的氮以形成并维持目前的气体状态。他们得出结论认为，如果这种机制确实是泰坦上氮云层形成的原因，那么月亮上的氮也应该来自于完全不同于地球的一种资源。

Catherine Neish在本期相关的“新闻和评述”中写道：“Sekine和同事提出的这种观点为未来的研究提供了一种可验证的假说。”（来源：科学时报王丹红/编译）

Replacement and late formation of atmospheric N2 on undifferentiated Titan by impacts

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Replacement and late formation of atmospheric N2 on undifferentiated Titan by impacts

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