| Project/Area Number |
11440158
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B).
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Petrology/Mineralogy/Science of ore deposit
|
|---|
| Research Institution | THE UNIVERISITY OF TOKYO |
|---|
Principal Investigator |
SASAKI Sho GRADUATE SCHOOL OF SCIENCE, THE UNIVERISITY OF TOKYO ASSOCIATE PROFESSOR, 大学院・理学系研究科, 助教授 (10183823)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
FUJIWARA Akira THE INSTITUTE OF SPACE AND ASTRONAUTICAL SCIENCE, PROFESSOR, 宇宙科学研究所, 教授 (70173482)
NAGAHARA Hiroko GRADUATE SCHOOL OF SCIENCE, THE UNIVERISITY OF TOKYO ASSOCIATE PROFESSOR, 大学院・理学系研究科, 助教授 (80172550)
SHIBATA Hiromi RESEARCH CENTER FOR NUCLEAR SCIENCE AND TECHNOLOGY, THE UNIVERISITY OF TOKYO ASSOCIATE PROFESSOR, 原子力研究総合センター, 助教授 (30216014)
OHASHI Hideo TOKYO UNIVERSITY OF FISHERIES, DEPARTMENT OF OCEAN SCIENCE, PROFESSOR, 水産学部, 教授 (40134647)
|
|---|
| Project Period (FY) |
1999 – 2000
|
| Project Status |
Completed (Fiscal Year 2000)
|
| Budget Amount *help |
¥9,400,000 (Direct Cost: ¥9,400,000)
Fiscal Year 2000: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1999: ¥8,000,000 (Direct Cost: ¥8,000,000)
|
|---|
| Keywords | SPACE WEATHERING / REFLECTANCE SPECTRUM / REGOLITH / ASTEROIDS / LUNAR SOIL / PULSE LASER / NANOPHASE PARTICLES / COLISSIONS OF INTERPLANETARY DUST PARTICLES / 赤化 / カンラン石 / 輝石 / 斜長石 / 蒸発と凝縮 |
|---|
| Research Abstract |
"Space weathering" is a proposed process responsible for the darkening and reddening of planetary surface materials and for decreasing depths of their optical absorption bands. It may explain the spectral mismatches between lunar soils and rocks as well as between asteroids and meteorites. The formation of nanophase iron particles on regolith grains due to micrometeorite impacts and/or solar wind irradiation is considered as the cause of the optical properties changes. Various laboratory simulations of space weathering have been performed. Nano-second pulse laser irradiation reproduced the optical changes associated with the space weathering. whereby compositional dependence of weathering of asteroids was also explained. However, the existence of nanophase iron particles has been a conjecture. Here we report observations of olivine samples after pulse-laser irradiation by transmission electron microscopy (TEM). Vapor-deposited amorphous rims of olivine grains have nanophase iron (aFe) particles (several to 30 nm in size) similar to those observed in lunar space weathering. Reduction by hydrogen atoms is not necessary to form nanophase iron particles. Our results should give additional support to the idea that ordinary chondrites have come from S-type asteroids, providing constraints on the surface exposure age of asteroids.
|
