小惑星イトカワワから帰還した粒子の中性子活性化分析
M Ebihara1, S Sekimoto, N Shirai
1Department of Chemistry, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan. ebihara-mitsuru@tmu.ac.jp
まとめ
ハヤブサ宇宙船の粒子の分析は,地球外生命体の起源と原始的な組成を示しています. その化学組成はコンドライトに似ていますが,金属成分にはイリジウムの濃度が低いです.
科学分野:
- 宇宙化学 (コスモケミストリー)
- 惑星科学は惑星科学である.
- アストロジオロジー アストロジオロジー
背景:
- 小惑星イトカワのサンプルは,ハヤブサミッションによって地球に戻されました.
- 小惑星のサンプルの組成を理解することは,初期の太陽系材料の洞察を提供します.
- 中性子活性化分析は,元素の組成を決定するための繊細な技術です.
研究 の 目的:
- 返還されたイトカワ小惑星の粒子の化学組成と起源を決定するために.
- イトカワサンプルの化学特性を,既知の隕石クラスと比較するために.
- 霧状凝縮プロセスに対するサンプル組成の影響を調査する.
主な方法:
- ハヤブサミッションのイトカワサンプルの1 ~ 3 マイクログラムの粒子が分析されました.
- 中性子活性化分析を用いて,粒子の元素組成を決定した.
- 主要な元素の比率 (Fe/Sc,Ni/Co,Ir/Ni,Ir/Coなど) を計算して比較した.
主要な成果:
- 穀物は主にオリヴィンで,少量のプラジオクラゼ,トロイライト,金属で構成されています.
- イトカワの試料は,コンドライトに似た化学特性 (Fe/Sc,Ni/Co比) を有しており,地球外の起源と原始的な組成を確認している.
- イトカワ検体の金属は,イリジウム/ニッケル,イリジウム/コバルトの比率がCI炭酸コンドリートより約5倍低く,通常のコンドリート金属に似ています.
結論:
- イトカワの穀物は地球外のものであり,原始的な化学組成を持っています.
- イトカワ検体の金属中のイリジウムの枯渇は,耐火性シデロフィール元素が既に分離されていた霧状環境から凝縮されたことを示唆しています.
- この発見は,太陽星雲の化学的進化と惑星粒子の形成の理解に貢献します.
関連する概念動画
Subatomic Particles
Dalton was only partially correct about the particles that make up matter. All matter is composed of atoms, and atoms are composed of three smaller subatomic particles: protons, neutrons, and electrons. These three particles account for the mass and the charge of an atom.
Atomic Emission Spectroscopy: Lab
AES is a powerful analytical technique, especially effective when used with plasma sources, producing abundant spectra in characteristic emission lines. The Inductively Coupled Plasma (ICP), in particular, yields superior quantitative analytical data due to its high stability, low noise, low background, and minimal interferences under optimal experimental conditions. However, newer air-operated microwave sources are emerging as promising alternatives that could be more cost-effective than...
Atomic Emission Spectroscopy: Overview
Atomic emission spectroscopy (AES) is an analytical technique used to determine the elemental composition of a sample by analyzing the light emitted from excited atoms. In AES, atoms in a sample are excited to higher energy levels by thermal energy from high-temperature sources, such as plasma, arcs, or sparks. When these excited atoms return to lower energy states, they emit light at specific wavelengths characteristic of each element. The resulting atomic emission spectrum, which consists of...
Nuclear Fission
Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger binding energies per nucleon—that is, mass numbers and binding energies per nucleon that are closer to the “peak” of the binding energy graph near 56. Sometimes neutrons are also produced. This decomposition of a large nucleus into smaller pieces is called fission. The breaking is rather random with the formation of a large number of different...
Atomic Absorption Spectroscopy: Atomization Methods
Atomic Absorption Spectroscopy (AAS) atomizes samples through flame atomization or electrothermal atomization. Flame atomization typically involves a nebulizer and spray chamber assembly to combine the sample with a fuel–oxidant mixture, creating a fine aerosol mist that enters a burner. Typically, the fuel and oxidant are combined in an approximately stoichiometric ratio. However, for atoms that are easily oxidized, a fuel-rich mixture may be more advantageous. Only about 5% of the aerosol...
Nuclear Transmutation
Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with another particle. The first manmade nucleus was produced in Ernest Rutherford’s laboratory in 1919 by a transmutation reaction, the bombardment of one type of nuclei with other nuclei or with neutrons. Rutherford bombarded nitrogen-14 atoms with high-speed α particles from a natural radioactive isotope of radium and observed protons being...


