Quantifying the Hypervolatile Abundances in Jupiter-family Comet 46P/Wirtanen

被引:14
作者
McKay, Adam J. J. [1 ,2 ]
DiSanti, Michael A. A. [1 ,3 ]
Cochran, Anita L. L. [4 ]
Bonev, Boncho P. P. [2 ]
Dello Russo, Neil [5 ]
Vervack, Ronald J. J. [5 ]
Gibb, Erika [6 ]
Roth, Nathan X. X. [1 ,7 ]
Saki, Mohammad [6 ]
Khan, Younas [6 ]
Kawakita, Hideyo [8 ]
机构
[1] NASA Goddard Space Flight Ctr, Solar Syst Explorat Div Code 690, Greenbelt, MD 20771 USA
[2] Amer Univ, Dept Phys, 4400 Massachusetts Ave NW, Washington, DC 20016 USA
[3] NASA Goddard Space Flight Ctr, Goddard Ctr Astrobiol, Greenbelt, MD 20771 USA
[4] Univ Texas Austin, McDonald Observ, 2515 Speedway,Stop C1402, Austin, TX 78712 USA
[5] Johns Hopkins Univ, Appl Phys Lab, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA
[6] Univ Missouri St Louis, Dept Phys, 1 Univ Blvd, St Louis, MO 63121 USA
[7] Univ Space Res Assoc, Columbia, MD USA
[8] Kyoto Sangyo Univ Motoyama, Koyama Astron Observ, Kita Ku, Kamigamo, Kyoto 6038555, Japan
来源
PLANETARY SCIENCE JOURNAL | 2021年 / 2卷 / 01期
基金
美国国家科学基金会;
关键词
FORBIDDEN OXYGEN LINES; C/1996; B2; HYAKUTAKE; C/2009; P1; GARRADD; VOLATILE COMPOSITION; ORGANIC VOLATILES; PARENT VOLATILES; 103P/HARTLEY; FRAGMENT-C; HALE-BOPP; WATER;
D O I
10.3847/PSJ/abd71d
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present analysis of IR and optical spectroscopy of Jupiter-family comet (JFC) 46P/Wirtanen obtained in 2019 January, when the comet had sufficient geocentric velocity to enable studies of the hypervolatiles CO and CH4, as well as [O i] emission. These species could not be studied near closest approach in mid-December because there was insufficient Doppler shift to separate the cometary emission from their corresponding telluric absorption lines. We employed the [O i] observations as a proxy for the CO2/H2O ratio, as CO2 cannot be observed directly from the ground, and space-based assets sensitive to CO2 were not able to observe 46P during this apparition. We focused our analysis on H2O, CO, CH4, C2H6, CH3OH, and CO2 (via [O i] emission). We detected strong emissions from H2O, C2H6, and CH3OH. Over the 3 nights, we found evidence for changing mixing ratios, mostly due to a variable H2O production rate. In 46P, C2H6 and CH3OH are enriched compared to cometary averages, with mixing ratios relative to H2O of similar to 1% and similar to 3%, respectively. Measurements of CH4 and CO have been especially rare in JFCs. We report significant 3 sigma upper limits on CH4/H2O < 0.97% and CO/H2O < 0.54%. They place CH4 being near-average or depleted, and CO being strongly depleted in 46P compared with Oort cloud comets. 46P has comparable CO/H2O to the few other measurements in JFCs, but enriched in C(2)H(6 )and CH3OH. Our inferred CO2/H2O mixing ratio is similar to 15%, though accounting for systematic uncertainties from the lack of knowledge of [O i] photochemistry means a value between 10% and 20% is likely. The compositional profile of 46P is similar to another small, hyperactive comet: 103P/Hartley 2. The mechanism of CO2-driven water-rich ice grain production proposed for 103P/Hartley 2 may be operating on 46P as well.
引用
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页数:12
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