Coma composition of comet 67P/Churyumov-Gerasimenko from radio-wave spectroscopy
Coma composition of comet 67P/Churyumov-Gerasimenko from radio-wave spectroscopy
复制标题
无线电波光谱中 67P/Churyumov-Gerasimenko 彗星的彗发成分
DOI：
10.1051/0004-6361/202245672
复制
发表时间：
2023
影响因子：
6.5
通讯作者：
Moreno, R.
中科院分区：
文献类型：
--
作者：
Biver, N.;Bockelée-Morvan, D.;Crovisier, J.;Sandqvist, Aa.;Boissier, J.;Lis, D. C.;Cordiner, M.;Bonev, B. P.;Dello Russo, N.;Moreno, R.
我们介绍了2021年11月至12月使用射电天文学研究所（IRAM）30米射电望远镜对67 P/Churyumov-Gerasimenko彗星进行分子调查的结果，当时它是几十年来最有利的现象。11月12日至16日期间，在IRAM 30米处的观测覆盖了3毫米处的8 GHz带宽、2毫米处的16 GHz带宽和1毫米窗口域中的60 GHz带宽。这些都是通过12月12日至13日的1毫米快照和2021年11月17日奥丁亚毫米天文台在557 GHz对H2O线的短暂观测以及Nançay射电望远镜对OH的18厘米观测完成的。还提供了在2015年9月18日至22日IRAM和2015年11月9日至12日Odin通过近日点时获得的较不敏感的观测结果。气体流出速度，放气模式，和温度已被精确地约束的观测。它们与2015年使用Rosetta/MIRO亚毫米仪器现场测量的结果完全一致。特别是，线的不对称性很好地表示为射流集中在约π球面度的四分之三的放气。我们推导出相对于水的7个分子和显着的上限约5人的丰度。检索的丰度进行了比较，在以前的近日点与罗塞塔原位测量。虽然HCN、CH 3OH和HNCO的那些是可比较的，但是发现67 P在H2S中耗尽并且在CS中相对正常（H2S/CS3），这与Rosetta/ROSINA质谱仪测量的H2S/CS2（100）丰度比强烈矛盾。虽然IRAM 30-m发现的甲醛总丰度，当假设它主要是由一个分布式源（Haser母尺度长度约8000 km）产生时，与Rosetta/ROSINA得出的结果相似，但我们发现，来自核的甲醛丰度比Rosetta/ROSINA原位测量的低一个数量级。
We present the results of a molecular survey of comet 67P/Churyumov-Gerasimenko undertaken with the Institut de RadioAstronomie Millimétrique (IRAM) 30-m radio telescope in November–December 2021, when it had its most favourable apparition in decades. Observations at IRAM 30-m during the 12–16 November period covered 8 GHz bandwidth at 3 mm, 16 GHz at 2 mm, and 60 GHz in the 1 mm window domain. These were completed by snapshots at 1 mm on 12–13 December and a short observation of the H2O line at 557 GHz with the Odin sub-millimetre observatory on 17.0 November 2021, and with 18-cm observations of OH with the Nançay radio telescope. Less sensitive observations obtained at a previous perihelion passage on 18–22 September 2015 with IRAM and 9–12 November 2015 with Odin are also presented. The gas outflow velocity, outgassing pattern, and temperature have been accurately constrained by the observations. They are perfectly consistent with those measured in situ with the Rosetta/MIRO sub-millimetre instrument in 2015. In particular, the asymmetry of the line is well represented by a jet concentrating three-quarters of the outgassing in aboutπsteradians. We derived abundances relative to water for seven molecules and significant upper limits for approximately five others. The retrieved abundances were compared to those measured in situ at the previous perihelion with Rosetta. While those of HCN, CH3OH, and HNCO are comparable, 67P is found to be depleted in H2S and relatively normal in CS (H2S/CS ≈ 3) in strong contradiction with the Rosetta/ROSINA mass spectrometer measurement of the H2S/CS2(≈100) abundance ratio. While the formaldehyde total abundance found with IRAM 30-m when assuming it to be mostly produced by a distributed source (Haser parent scale length ≈8000 km) is similar to the one derived by Rosetta/ROSINA, we find that the formaldehyde coming from the nucleus is one order of magnitude less abundant than measured in situ by Rosetta/ROSINA.