Exploring material transportation in the solar nebula from the isotopic ratios of various molecules and the thermal history of minerals in comets

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K14541
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 17010:Space and planetary sciences-related
• Research Institution: Kyoto Sangyo University
• Principal Investigator: Shinnaka Yoshiharu 京都産業大学, 神山天文台, 専任専門員 (60774429)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 彗星 / 原始太陽系円盤

Outline of Final Research Achievements

To understand the transportation of materials in the solar nebula, we conducted research using comets as probes. The formation temperature of the comet was estimated from the abundance ratio of H2O, CO2, and CO, which are the main components of cometary icy materials. The formation distance of the comet nucleus was estimated from the mineral composition, and the properties of the dust grains were estimated from the spatial distribution of the polarization degree in the coma. As a result of applying these methods to the 21P comet, it was shown that this comet was formed in a warm place despite being at the same distance as other comets. By applying this method to other comets, we will advance statistical discussions on the transport of materials in the solar nebula. In addition, we applied the physical model developed for estimating the formation temperature to the spatial distribution of the coma of the C/2014 Q2 comet, and revealed that NH3 is being generated as a secondary product.

Free Research Field

太陽系小天体

Academic Significance and Societal Importance of the Research Achievements

彗星は46億年前に原始太陽系円盤で作られた氷微惑星の残存物であり、太陽系の化石とも呼ばれる。彗星には高温度生成物と低温度生成物が含まれており、原始太陽系円盤中での大規模な物質輸送の存在が指摘されている。
本研究において、同一彗星の揮発性分子の元素組成比や同位体比と鉱物の熱履歴等を組み合わせることで、従来より詳細に原始惑星系円盤での彗星核の形成環境を推定する手法を確立した。さらに、本研究課題で開発した彗星コマの物理モデルを用いることで、彗星コマ中の化学反応を再現できることを示した。これらの手法は他の彗星や他の分子についても適用可能で、統計的な議論を進めるための基礎情報を提供する。