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arXiv 1808.03329astro-ph.EP
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前太阳星云中面颗粒表面彗星O $_{2}$冰和相关冰种类的形成

Formation of cometary O$_{2}$ ice and related ice species on grain surfaces in the midplane of the pre-Solar nebula

Christian Eistrup, Catherine Walsh

备注：
Accepted for publication in Astronomy and Astrophysics. 22 pages, 15 figures
发表信息：
A&A 621, A75 (2019)
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摘要：

[摘要]在1 P/哈雷彗星和67 P/丘留莫夫-格拉西缅科彗星的彗发中检测到相对于H $_{2}$ O冰为1-10%的O $_{2}$冰，这促使人们试图解释高O $_{2}$冰丰度的起源。最近对原行星盘中平面外部较冷区域的化学建模表明，O $_{2}$冰的产生与彗星中测量到的相同。一个更新的化学动力学代码在这里使用前太阳星云中平面条件下的化学演变。试验了四种不同的化学启动条件，以及各种化学参数的影响。参数空间研究揭示了O $_{2}$冰的最佳生产点，其丰度与67 P和1 P中的丰度相匹配，O $_{3}$和H $_{2}$ O $_{2}$冰的丰度与67 P中的丰度相匹配。这意味着在前太阳星云的120-150 AU的径向区域内，O $_{2}$可能是通过颗粒表面的冰化学原位产生的。然而，很明显的是，化学对假定的化学参数（例如，结合能、激活势垒宽度和量子隧穿势垒）具有高度的敏感性。因此，因为更可能的情况下，以锁定在O $_{2}$中的元素氧的百分比开始，也再现了早期阶段67 P中O $_{2}$冰的丰度，这支持了以前的建议，即彗星O $_{2}$冰可能具有原始起源。

英文摘要：

[Abridged] The detection of abundant O$_{2}$ ice at 1-10% with respect to H$_{2}$O ice in the comae of comets 1P/Halley and 67P/Churyumov-Gerasimenko motivated attempts to explain the origin of the high O$_{2}$ ice abundance. Recent chemical modelling of the outer, colder regions of a protoplanetary disk midplane has shown production of O$_{2}$ ice at the same abundance as that measured in the comet. An updated chemical kinetics code is utilised here to evolve chemistry under pre-Solar nebula midplane conditions. Four different chemical starting conditions, and the effects of various chemical parameters are tested. The parameter space investigation revealed a sweet spot for production of O$_{2}$ ice at an abundance matching those in 67P and 1P, and O$_{3}$ and H$_{2}$O$_{2}$ ices abundances matching those in 67P. This means that there is a radial region in the pre-Solar nebula from 120-150 AU, within which O$_{2}$ could have been produced in-situ via ice chemistry on grain surfaces. However, it is apparent that there is a high degree of sensitivity of the chemistry to the assumed chemical parameters (e.g. binding energy, activation barrier width, and quantum tunnelling barrier). Hence, because the more likely scenario starting with a percentage of elemental oxygen locked in O$_{2}$ also reproduces the O$_{2}$ ice abundance in 67P at early stages, this supports previous suggestions that the cometary O$_{2}$ ice could have a primordial origin.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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