Mineralogical Study of Extraterrestrial Materials
- NOGUCHI Takaaki†, Professor
- † Faculty of Arts and Science
- We are investigating various kinds of extraterrestrial materials (meteorites, micrometeorites, returned samples from moon, 25143 asteroid Itokawa, 81P/Wild 2 comet, and international space station) based on mineral science. Especially, we try to reveal histories of these extraterrestrial materials based on the observation and analysis on the nanometer scale by using transmission electron microscopy. In addition, interdisciplinary studies become increasingly important to understand what happened in or on the solar system bodies in detail. We started to collaborate with R. Okazaki (noble gas study) and H. Naraoka (organic geo- and cosmochemistry). The collaborative work will serve to investigate samples from asteroid Ryugu, the target asteroid of Hayabusa 2.
Three images of scientific results performed by our laboratory
1. Cometary dust found on the surface of the earth
Upper image is a cometary dust particle found on the surface of the earth. This image was taken by a scanning electron microscope (SEM) (secondary electron image). A kind of extraterrestrial materials, called called interplanetary dust particles (IDPs), has been collected flying in the stratosphere by using a special airplane. Among them, chondritic porous (CP) IDPs have been regarded as cometary dust based on mineralogical and cosmochemical evidences. It has been thought that it is impossible to obtain them on the ground because they are extremely porous and fragile. We found that they are preserved in surface snow in Antarctica and moreover, they preserved in Antarctic ice as rare cases. This image was selected as one of the 2014 Top 10 Science Images by Science.com.
2. Space weathering on Itokawa grains
The surface material exposed direct to the interplanetary space experiences irradiation by solar wind (plasma flow from the Sun), solar and galactic cosmic rays (high energy charged particles), and micrometeoroid impacts. We found that the surface modification of the Itokawa grains is mainly promoted by irradiation of solar wind and solar cosmic rays. Middle image was taken by a transmission electron microscope (TEM) by using ~0.1 µm thick sample of an Itokawa grain (dark field image). The bright band (rim) was formed by solar wind irradiation and white lines indicated by arrows were formed by solar flare particles.
3. A fine-grained particle captured on the ISS
JAXA captured fine-grained particles on the international space station (ISS) from 2000 to 2005 and 2010. Lower image was taken by TEM by using ~0.1 µm thick sample of a tiny grain captured at the outside of the Kibo module. This grain is probably secondary debris, a mixture of melted natural and artificial materials. At present, only one micrometeoroid (natural sample) was found among tiny grains captured at the ISS. Our group found it and investigated.