Observation of Itokawa samples to understand the mechanism of sulfur depletion on asteroids.

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K13610
• 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: Kyushu University
• Principal Investigator: Matsumoto Toru 九州大学, 基幹教育院, 特別研究員(PD) (80750455)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 小惑星 / イトカワ / 宇宙風化 / 硫化鉄 / 金属鉄

Outline of Final Research Achievements

In this project, I (and co-workers) investigated surface structures of regolith particles recovered from asteroid Itokawa by the Hayabusa mission. I found metallic iron whiskers on iron sulfides (FeS) in the particles. The whiskers are newly found nano-structures among extraterrestrial materials and were likely formed via selective sulfur loss from the surface of iron sulfides caused by solar wind irradiation. I proposed that ion irradiation may play a fundamental role in the chemical evolution of iron and sulfur in the space environment.

Free Research Field

惑星物質科学

Academic Significance and Societal Importance of the Research Achievements

NASAの小惑星探査によって、小惑星表面では硫黄のみが隕石物質に比べて欠乏していることが示唆されていたが、その具体的な仕組みは長年解明されていなかった。本研究は硫黄の消失が実際に小惑星表面で起きる証拠とその仕組みを初めて示した。この成果は、観測から小天体の化学組成を正確に推定し、太陽系惑星の構成物となった小惑星の材料やその進化の解明に役立つと期待される。