We investigate the enrichment patterns of several delivery scenarios of the volatiles to the atmospheres of ice giants, having in mind that the only well constrained determination made remotely, namely the carbon abundance measurement, suggests that their envelopes possess highly supersolar metallicities, i.e., close to two orders of magnitude above that of the protosolar nebula. In the framework of the core accretion model, only the delivery of volatiles in solid forms (amorphous ice, clathrates, pure condensates) to these planets can account for the apparent supersolar metallicity of their envelopes. In contrast, because of the inward drift of icy particles through various snowlines, all mechanisms invoking the delivery of volatiles in vapor forms predict subsolar abundances in the envelopes of Uranus and Neptune. Alternatively, even if the disk instability mechanism remains questionable in our solar system, it might be consistent with the supersolar metallicities observed in Uranus and Neptune, assuming the two planets suffered subsequent erosion of their H-He envelopes. The enrichment patterns derived for each delivery scenario considered should be useful to interpret future in situ measurements by atmospheric entry probes.

中文翻译：

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确定天王星和海王星挥发物源库的关键大气特征

我们研究了几种挥发物向冰巨星大气的输送情景的富集模式，考虑到远程进行的唯一受限制的确定，即碳丰度测量，表明它们的包层具有高度的超太阳金属丰度，即接近比原太阳星云高两个数量级。在核心吸积模型的框架中，只有以固体形式（无定形冰、包合物、纯冷凝物）向这些行星输送挥发物才能解释其外壳的明显超太阳金属丰度。相比之下，由于冰粒子通过各种雪线向内漂移，所有以蒸气形式输送挥发物的机制都预测了天王星和海王星包层中的太阳下丰度。或者，即使我们的太阳系中圆盘不稳定机制仍然存在问题，但它可能与在天王星和海王星中观察到的超太阳金属丰度一致，假设这两个行星的 H-He 包层随后遭受侵蚀。为所考虑的每个交付场景得出的富集模式应该有助于解释未来大气进入探测器的原位测量。