詹姆斯·韦布空间望远镜（JWST）对星尘的研究：I. 81P/怀尔德2号彗星的红外光谱与整体成分
A JWST Study of Stardust. I. Infrared Spectroscopy of Comet 81P/Wild 2 and Overall Composition
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中文总结 AI 辅助
本研究利用JWST对81P/怀尔德2号彗星开展红外观测，探测多种分子并确定彗核与尘埃参数，将其与星尘返回样本对比，揭示两项任务对彗发尘埃的探测互补性。
中文摘要 AI 辅助
我们报告了对星尘（Stardust）样本返回任务目标——81P/怀尔德2号彗星的观测，观测于2023年3月20日和24日（世界时）开展，当时的日心距离（$r_H$）为1.85天文单位（au），使用的是詹姆斯·韦布空间望远镜（JWST）上的近红外光谱仪（NIRSpec）和中红外仪器（MIRI）积分场单元光谱仪。本研究是首次将JWST对太阳系天体的遥感光谱观测，与对其返回样本的地面分析进行成分对比的研究。我们可靠探测到了H₂O、CH₄、C₂H₆、CH₃OH、CO、CO₂、¹³CO₂、OCS、HCN和CN的分子发射，发现这些分子丰度与此前近日点通过期间报道的结果在2σ范围内一致。水的正-仲比为2.76±0.05，¹²CO₂/¹³CO₂比值为85±4。我们探测并建模了彗核与尘埃的热发射，得到有效彗核半径为1.77±0.04 km，亚微米级尘埃颗粒的相对质量分数成分为：约36%无定形碳、约25%无定形镁铁橄榄石、约23%富镁结晶橄榄石、约15%无定形镁铁辉石。彗发中亚微米级颗粒的结晶质量分数为0.362±0.003。将JWST得到的热模型与星尘（Stardust）返回样本中的细颗粒物质对比，表明两项任务具有互补性，各自对彗发尘埃颗粒的不同群体最为敏感。
英文摘要
We report observations of comet 81P/Wild 2, target of the Stardust sample return mission, on UT 2023 March 20 and 24 at a heliocentric distance ($r_H$) of 1.85 au using the NIRSpec and MIRI integral field unit spectrographs on board the James Webb Space Telescope (JWST). This study is the first compositional comparison between JWST remote-sensing spectroscopy of a solar system object against terrestrial analysis of its returned samples. We securely detected molecular emission from H$_2$O, CH$_4$, C$_2$H$_6$, CH$_3$OH, CO, CO$_2$, $^{13}$CO$_2$, OCS, HCN, and CN and find molecular abundances consistent within $2σ$ with those reported during previous perihelion passages. The water ortho-to-para ratio was $2.76\pm0.05$, and the $^{12}$CO$_2$/$^{13}$CO$_2$ ratio was $85\pm4$. Thermal emission from the nucleus and dust was detected and modeled, providing an effective nucleus radius of $1.77\pm0.04$ km and a dust composition (relative mass fraction of the submicron grains) of $\sim36\%$ amorphous carbon, $\sim25\%$ amorphous Mg:Fe olivine, $\sim23\%$ Mg-rich crystalline olivine, and $\sim15\%$ amorphous Mg:Fe pyroxene. The crystalline mass fraction of the sub-micron grains in the coma was $0.362\pm0.003$. Comparison of the JWST-derived thermal model against the fine-grained materials in Stardust returned samples demonstrates complementarity between the missions, with each most sensitive to a different population of the coma dust grains.
