Delivery of water and organics by asteroid and comet impacts may have influenced prebiotic chemistry on the early Earth. Some recent prebiotic chemistry experiments emphasize hydrogen cyanide (HCN) as a feedstock molecule for the formation of sugars, ribonucleotides, amino acids, and lipid precursors. Here, we assess how much HCN originally contained in a comet would survive impact, using parametric temperature and pressure profiles together with a time-dependent chemistry model. We find that HCN survival mainly depends on whether the impact is hot enough to thermally decompose H₂O into reactive radicals, and HCN is therefore rather insensitive to the details of the chemistry. In the most favorable impacts (low impact angle, low velocity, small radius), this temperature threshold is not reached, and intact delivery of HCN is possible. We estimate the global delivery of HCN during a period of Early and Late Heavy Bombardment of the early Earth, as well as local HCN concentrations achieved by individual impacts. In the latter case, comet impacts can provide prebiotically interesting HCN levels for thousands to millions of years, depending on properties of the impactor and of the local environment.

中文翻译：

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氰化氢向地球早期的彗星传递。

小行星和彗星撞击所产生的水和有机物可能已经影响了地球早期的益生元化学。最近的一些益生元化学实验强调了氰化氢（HCN）作为形成糖，核糖核苷酸，氨基酸和脂质前体的原料分子。在这里，我们使用参数温度和压力曲线以及随时间变化的化学模型来评估彗星中最初包含的HCN在撞击后仍能幸免。我们发现，HCN的存活主要取决于撞击的温度是否足以使H ₂热分解。O变成反应性自由基，因此HCN对化学细节不敏感。在最有利的冲击下（低冲击角，低速度，小半径），无法达到该温度阈值，并且可以完整递送HCN。我们估计了早期地球的早期和晚期重轰炸期间HCN的全球交付量，以及通过个别影响实现的局部HCN浓度。在后一种情况下，彗星撞击可提供数千到数百万年的益生元有趣的HCN含量，这取决于撞击物和当地环境的特性。