The formation of the gas giant planets Jupiter and Saturn probably required the growth of massive ∼ 15 Earth-mass cores on a time scale shorter than the ∼ 107 time scale for removal of nebular gas. Relatively minor variations in nebular parameters could preclude the growth of full-size gas giants even in systems in which the terrestrial planet region is similar to our own. Systems containing “failed Jupiters,” resembling Uranus and Neptune in their failure to capture much nebular gas, would be expected to contain more densely populated cometary source regions. They will also eject a smaller number of comets into interstellar space. If systems of this kind were the norm, observation of hyperbolic comets would be unexpected. Monte Carlo calculations of the orbital evolution of region of such systems (the Kuiper belt) indicate that throughout Earth history the cometary impact flux in their terrestrial planet regions would be ∼ 1000 times greater than in our Solar System. It may be speculated that this could frustrate the evolution of organisms that observe and seek to understand their planetary system. For this reason our observation of these planets in our Solar System may tell us nothing about the probability of similar gas giants occurring in other planetary systems. This situation can be corrected by observation of an unbiased sample of planetary systems.

中文翻译：

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木星缺失的可能后果？在行星系统中

气态巨行星木星和土星的形成可能需要在比去除星云气体的~107 时间尺度更短的时间尺度上生长~15 个地球质量核心。即使在类地行星区域与我们相似的系统中，星云参数相对较小的变化也可能阻止全尺寸气态巨行星的生长。包含“失败的木星”的系统，类似于天王星和海王星未能捕获大量星云气体，预计将包含人口更稠密的彗星源区。它们还将向星际空间喷射少量彗星。如果这种系统成为常态，那么对双曲彗星的观察将是出乎意料的。此类系统（柯伊伯带）区域轨道演化的蒙特卡罗计算表明，在整个地球历史上，它们的类地行星区域的彗星撞击通量将比我们的太阳系大 1000 倍。可以推测，这可能会阻碍观察并试图了解其行星系统的生物体的进化。出于这个原因，我们对太阳系中这些行星的观察可能无法告诉我们其他行星系统中出现类似气态巨行星的可能性。这种情况可以通过观察行星系统的无偏见样本来纠正。可以推测，这可能会阻碍观察并试图了解其行星系统的生物体的进化。出于这个原因，我们对太阳系中这些行星的观察可能无法告诉我们其他行星系统中出现类似气态巨行星的可能性。这种情况可以通过观察行星系统的无偏见样本来纠正。可以推测，这可能会阻碍观察并试图了解其行星系统的生物体的进化。出于这个原因，我们对太阳系中这些行星的观察可能无法告诉我们其他行星系统中出现类似气态巨行星的可能性。这种情况可以通过观察行星系统的无偏见样本来纠正。