67 P/Churyumov-Gerasimenko彗星的COSAC和Ptolemy质谱衰变
Decay of COSAC and Ptolemy Mass Spectra at Comet 67P/Churyumov-Gerasimenko
摘要：
2014年11月12日，罗塞塔着陆器菲莱成功降落在彗星67 P/Churyumov-Gerasimenko的核上。菲莱配备了两个气体分析仪：彗星采样和成分实验（COSAC）和气相色谱仪和质谱仪托勒密。2014年11月12日至14日，两台仪器在菲莱跳跃期间和在其最后着陆点阿拜多斯以嗅探模式进行了七次测量，测量了彗星核物质的有机组成。我们比较了两种质谱仪确定的几种离子的强度的时间演变。对于COSAC，这是第一次分析测量的离子种类的时间行为。在菲莱第一次降落在阿比多斯后约20至30分钟，所有离子种类在两台仪器测量的第一次光谱中显示出最高强度，并在阿比多斯连续六次测量期间出现衰减。两种仪器都测量到水峰（m/z 18）几乎相同的衰减，CO（m/z 28）表现相似。在COSAC测量中，m/z 44处的峰比所有其他离子种类（包括水峰）衰减得慢得多。特别地，m/z 44峰在COSAC测量中比在Ptolemy数据中衰减得慢得多。这支持了我们先前的解释，即COSAC第一次分析了来自彗星核的风化层样品，而托勒密测量了来自环境昏迷的彗星气体。通过COSAC测量的m/z 44峰可能主要由有机物质组成，而通过Ptolemy测量的峰被解释为主要由$CO_2$组成。比m/z 30重的离子种类在COSAC测量中比在Ptolemy数据中衰减得稍慢，这可能与两种仪器之间排气设计的差异有关。
英文摘要：
The Rosetta lander Philae successfully landed on the nucleus of comet 67P/Churyumov-Gerasimenko on 12 November 2014. Philae is equipped with two gas analyzers: The Cometary Sampling and Composition experiment (COSAC) and the gas chromatograph and mass spectrometer Ptolemy. On 12 to 14 November 2014 both instruments measured the organic composition of the comet nucleus material through seven measurements in sniffing mode during Philae's hopping and at its final landing site Abydos. We compare the temporal evolution of intensities of several ion species identified by both mass spectrometers. For COSAC this is the first analysis of the temporal behaviour of the measured ion species. All ion species showed the highest intensities in the first spectra measured by both instruments about 20 to 30 minutes after Philae's first touchdown at Agilkia, and a decay during the six consecutive measurements at Abydos. Both instruments measured a nearly identical decay of the water peak (m/z 18), and also CO (m/z 28) behaved similarly. In the COSAC measurements the peak at m/z 44 decays much slower than all the other ion species, including the water peak. In particular, the m/z 44 peak decays much slower in the COSAC measurements than in the Ptolemy data. This supports our earlier interpretation that COSAC for the first time analyzed a regolith sample from a cometary nucleus in situ, while Ptolemy measured cometary gas from the ambient coma. The m/z 44 peak measured by COSAC was likely dominated by organic species, whereas the peak measured by Ptolemy was interpreted to be mostly due to $CO_2$. Ion species heavier than m/z 30 tend to decay somewhat slower in the COSAC measurements than in the Ptolemy data, which may be related to differences in the exhaust designs between both instruments.
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