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 ∼1% and ∼3%, respectively. Measurements of CH₄ and CO have been especially rare in JFCs. We report significant 3σ 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 C₂H₆ and CH₃OH. Our inferred CO₂/H₂O mixing ratio is ∼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.

我们对2019年1月获得的木星家族彗星（JFC）46P / Wirtanen的红外光谱和光谱学进行了分析，当时该彗星具有足够的地心线速度，可以研究高挥发性CO和CH ₄以及[O i ]排放。由于没有足够的多普勒频移将彗星的发射与其相应的碲吸收线区分开来，因此无法在12月中旬附近研究这些物种。我们所用的〔O我]观测作为CO的代理₂ / H ₂ O比，如CO ₂不能直接从地面观察，以及CO基于空间的资产敏感₂在这次幻影中无法观察到46P。我们将分析重点放在了H ₂ O，CO，CH ₄，C ₂ H ₆，CH ₃ OH和CO ₂（通过[O i ]发射）上。我们检测到H ₂ O，C ₂ H ₆和CH ₃ OH的强烈排放。在3个晚上的时间里，我们发现了改变混合比的证据，主要是由于H ₂ O产生速率的变化。与彗星平均值相比，在46P中，C ₂ H ₆和CH ₃ OH富集，相对于H _2的混合比O分别为〜1％和〜3％。在JFC中，CH ₄和CO的测量尤为罕见。我们报告了CH ₄ / H ₂ O <0.97％和CO / H ₂ O <0.54％的3σ上限。与奥特云彗星相比，它们使CH ₄接近平均或已耗尽，而CO在46P中被严重耗尽。46P的CO / H ₂ O可以与JFC中的其他几项测量值相提并论，但富含C ₂ H ₆和CH ₃ OH。我们推断的CO ₂ / H ₂ O混合比约为15％，尽管由于缺乏对[O i光化学意味着该值可能在10％到20％之间。46P的组成特征类似于另一个小的活动过度的彗星：103P / Hartley2。针对103P / Hartley 2提出的CO ₂驱动的富水冰粒生产机制也可能在46P上运行。