近日，美国马里兰大学的Michael S. P.Kelley与美国大学天文学研究协会的Heidi B.Hammel以及NASA戈达德太空飞行中心的Stefanie N.Milam等人合作，并取得一项新进展。经过不懈努力，他们实现了主带彗星水蒸汽排放的光谱识别。相关研究成果已于2023年5月15日在国际权威学术期刊《自然》上发表。

该研究团队利用JWST的观测结果清晰地展示了主带彗星238P/Read的特征。观测结果表明，该彗星存在水蒸汽的彗发活动，但没有明显的CO₂气体彗发。这一研究结果揭示了彗星Read的活动是由水冰的升华所驱动的，并表明主带彗星与一般彗星群体在本质上存在差异。这意味着彗星Read可能经历了不同的形成环境或演化历史，并且不太可能是最近从外太阳系进入小行星带的天体。基于这些结果，主带彗星似乎代表了目前在经典彗星观测和陨石记录中未被代表的挥发物质样本，因此对于理解早期太阳系中的挥发物库存及其随后的演化具有重要意义。

据悉，主带彗星是太阳系小行星带中的小型天体，当它们接近近日点时会出现类似彗星的活动，例如尘埃喷发或形成尾巴，这明显暗示了冰的升华过程。尽管主带彗星的存在意味着小行星带中可能存在尚未消失的水冰，然而，通过对这些天体进行密集观测，使用世界上最大的望远镜，尚未探测到围绕它们的气体存在。

附：英文原文

Title: Spectroscopic identification of water emission from a main-belt comet

Author: Kelley, Michael S. P., Hsieh, Henry H., Bodewits, Dennis, Saki, Mohammad, Villanueva, Geronimo L., Milam, Stefanie N., Hammel, Heidi B.

Issue&Volume: 2023-05-15

Abstract: Main-belt comets are small solar system bodies located in the asteroid belt that repeatedly exhibit comet-like activity (i.e., dust comae or tails) during their perihelion passages, strongly suggesting ice sublimation.^1,2 Although the existence of main-belt comets implies the presence of extant water ice in the asteroid belt, no gas has been detected around these objects despite intense scrutiny with the world’s largest telescopes.³ Here, we present JWST observations which clearly show that main-belt comet 238P/Read has a coma of water vapour, but lacks a significant CO₂ gas coma. Our findings demonstrate that the activity of comet Read is driven by water-ice sublimation, and implies that main-belt comets are fundamentally different from the general cometary population. Whether comet Read experienced different formation circumstances or evolutionary history, it is unlikely to be a recent asteroid belt interloper from the outer solar system. Based on these results, main-belt comets appear to represent a sample of volatile material that is currently unrepresented in observations of classical comets and the meteoritic record, making them important for understanding the early solar system’s volatile inventory and its subsequent evolution.

DOI: 10.1038/s41586-023-06152-y

Source: https://www.nature.com/articles/s41586-023-06152-y