Shoemaker-Levy 9 – AEAS精读 (Y10-12)

In July of 1994, an astounding series of events took place. The world anxiously watched as, every few hours, a hurtling chunk of comet plunged into the atmosphere of Jupiter. All of the twenty-odd fragments, collectively called comet Shoemaker-Levy 9 after its discoverers, were once part of the same object, now dismembered and strung out along the same orbit. This cometary train, glistening like a string of pearls, had been first glimpsed only a few months before its fateful impact with Jupiter, and rather quickly scientists had predicted that the fragments were on a collision course with the giant planet. The impact caused an explosion clearly visible from Earth, a bright flaming fire that quickly expanded as each icy mass incinerated itself. When each fragment slammed at 60 kilometers per second into the dense atmosphere, its immense kinetic energy was transformed into heat, producing a superheated fireball that was ejected back through the tunnel the fragment had made a few seconds earlier. The residues from these explosions left huge black marks on the face of Jupiter, some of which have stretched out to form dark ribbons.

Although this impact event was of considerable scientific import, it especially piqued public curiosity and interest. Photographs of each collision made the evening television newscast and were posted on the Internet. This was possibly the most open scientific endeavor in history. The face of the largest planet in the solar system was changed before our very eyes. And for the very first time, most of humanity came to fully appreciate the fact that we ourselves live on a similar target, a world subject to catastrophe by random assaults from celestial bodies. That realization was a surprise to many, but it should not have been. One of the great truths revealed by the last few decades of planetary exploration is that collisions between bodies of all sizes are relatively commonplace, at least in geologic terms, and were even more frequent in the early solar system.

 

1994年7月发生了一系列令人震惊的事件。全世界都在焦急地注视着,每隔几个小时就有一颗彗星飞入木星的大气层。所有这20多块碎片,统称为苏梅克-列维9号彗星(以其发现者的名字命名),都曾是同一物体的一部分,现在被肢解并沿着同一轨道排列。这列彗星列车像一串珍珠一样闪闪发光,在它与木星发生致命撞击的几个月前才第一次被看到,科学家们很快就预测这些碎片将与木星发生碰撞。撞击造成了从地球上可以清楚看到的爆炸,明亮的火焰随着每一块冰原的燃烧而迅速膨胀。当每个碎片以每秒60公里的速度撞击到稠密的大气层时,其巨大的动能转化为热能,产生一个过热的火球,火球被弹回到碎片几秒钟前形成的隧道中。这些爆炸的残留物在木星表面留下了巨大的黑色痕迹,其中一些已经伸展成黑色的带状。

虽然这次撞击事件具有重大的科学意义,但它尤其激起了公众的好奇心和兴趣。每次碰撞的照片都在晚间电视新闻中播出,并被发布在互联网上。这可能是历史上最开放的科学尝试。太阳系中最大的行星在我们眼前发生了巨大的变化。大多数人类第一次充分认识到,我们自己也生活在一个类似的目标上,一个受到来自天体随机袭击的灾难的世界。这一认识令许多人感到意外,但本不应如此。过去几十年的行星探索揭示了一个伟大的事实,那就是各种大小的天体之间的碰撞相对来说是很常见的,至少从地质学的角度来看是这样,在太阳系早期甚至更为频繁。