Probing the Evolutionary History of Comets: An Investigation of the Hypervolatiles CO, CH4, and C2H6 in the Jupiter-family Comet 21P/Giacobini–Zinner
Probing the Evolutionary History of Comets: An Investigation of the Hypervolatiles CO, CH4, and C2H6 in the Jupiter-family Comet 21P/Giacobini–Zinner
复制标题
探索彗星的进化史：木星家族彗星 21P/Giacobini-Zinner 中高挥发物 CO、CH4 和 C2H6 的研究
作者：
N. Roth;E. Gibb;B. Bonev;M. DiSanti;N. Russo;A. McKay;R. Vervack;H. Kawakita;M. Saki;N. Biver;D. Bockelée;L. Feaga;N. Fougere;A. Cochran;M. Combi;Y. Shou
要了解储存在彗星核中的母挥发物中编码的宇宙起源记录，需要调查在连续的近日点通过期间，演化（热演化或其他演化）是否改变了短周期彗星的组成。作为彗星中系统观测到的最易挥发的分子，短周期彗星中CO、CH 4和C2 H6的丰度可能有助于阐明在设定当今组成时纳塔尔条件和形成后演化之间的相互作用，但在彗星族彗星（JFC）中CO和CH 4的安全测量尤其稀少。2018年JFC 21 P/Giacobini-Zinner的出现非常有利，使得在一颗原型碳链耗尽的彗星中对这些“高挥发物”进行了灵敏的搜索。我们观察21 P/Giacobini-Zinner与iSHELL光谱仪在美国宇航局红外望远镜设施的四个前近日点日期，两个日期近近日点，和一个后近日点日期。我们在多个日期同时检测到CO、CH 4和C2 H6和H2O。我们目前的旋转温度，生产率和混合比。结合以前的工作，我们的研究结果可能表明，21 P/Giacobini-Zinner的高挥发性彗发组成是可变的幻影，以及在一个特定的近日点通道，但在这些测量的蔓延是一个相对较小的部分，在每个分子的变化，从彗星到彗星。我们讨论了我们测量的21 P/Giacobini-Zinner的JFC的演变的超挥发分含量的影响，并将我们的结果的背景下，罗塞塔使命和地面彗星的研究结果。
Understanding the cosmogonic record encoded in the parent volatiles stored in cometary nuclei requires investigating whether evolution (thermal or otherwise) has modified the composition of short-period comets during successive perihelion passages. As the most volatile molecules systematically observed in comets, the abundances of CO, CH4, and C2H6 in short-period comets may serve to elucidate the interplay between natal conditions and post-formative evolution in setting present-day composition, yet secure measurements of CO and CH4 in Jupiter-family comets (JFCs) are especially sparse. The highly favorable 2018 apparition of JFC 21P/Giacobini–Zinner enabled a sensitive search for these “hypervolatiles” in a prototypical carbon-chain depleted comet. We observed 21P/Giacobini–Zinner with the iSHELL spectrograph at the NASA Infrared Telescope Facility on four pre-perihelion dates, two dates near-perihelion, and one post-perihelion date. We obtained detections of CO, CH4, and C2H6 simultaneously with H2O on multiple dates. We present rotational temperatures, production rates, and mixing ratios. Combined with previous work, our results may indicate that the hypervolatile coma composition of 21P/Giacobini–Zinner was variable across apparitions as well as within a particular perihelion passage, yet the spread in these measurements is a relatively small fraction of the variation in each molecule from comet to comet. We discuss the implications of our measured hypervolatile content of 21P/Giacobini–Zinner for the evolution of JFCs, and place our results in the context of findings from the Rosetta mission and ground-based studies of comets.