巨大衝突後の地球の冷却と核の形成
Bernard J Wood1, Alex N Halliday
1Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK. bwood@els.mq.edu.au
Nature
|October 28, 2005
まとめ
地球 地球 地球 地球 地球 地球
科学分野:
- 地質物理学 地質物理学とは地質物理学です.
- 惑星科学は惑星科学である.
- 地質化学 地質化学
背景:
- ケルヴィン卿は,導電性冷却に基づいて,地球の年齢を2400万年と見積もった.
- 月を形成した巨大衝突は,地球の熱状態と組成を大幅に変化させた.
- U-PbとHf-Wの同位体系には,地球の蓄積と核分離の時間スケールに関する不一致がある.
研究 の 目的:
- U-PbとHf-W同位体系から派生した異なる時間スケールを説明する.
- 初期の地球冷却モデルと地質学的および同位体学的証拠を調和させる.
- 後期段階の核分離のメカニズムとその地球年齢への影響について提案する.
主な方法:
- タイムスケールを決定するために,同位体システム (U-PbとHf-W) の分析.
- 地球の冷却とコアの分離過程のモデリング.
- 巨大衝突とマントルの結晶化の役割を調査する.
主要な成果:
- Hf-Wのタイムスケールは,月形成の衝突前の核形成を反映しています.
- 巨大衝突時の酸化は,硫黄に富んだ金属核の遅い分離につながった.
- この遅い分離は,月形成の衝撃から30 +/- 10 Myr後に発生し,地球のU-Pb年代測定を説明しています.
- この期間に地球は約4000K冷却され,ケルビンの冷却推定値と一致した.
結論:
- 2段階の核形成プロセスは,異なる同位体時間スケールを調和させます.
- 酸化と遅い金属分離は,地球の初期の熱的進化に大きな影響を与えた.
- 提案されたモデルは,初期の地球の歴史と冷却のより包括的な理解を提供します.
関連する概念動画
Global Climate Change
Throughout its ~4.5 billion year history, the Earth has experienced periods of warming and cooling. However, the current drastic increase in global temperatures is well outside of the Earth’s cyclic norms, and evidence for human-caused global climate change is compelling. Paleoclimatology, the study of ancient climate conditions, provides ample evidence for human-caused global climate change by comparing recent conditions with those in the past.
Conditions on Early Earth
Around 4 billion years ago, oceans began to condense on earth while volcanic eruptions released nitrogen, carbon dioxide, methane, ammonia, and hydrogen into the primordial atmosphere. However, organisms with the characteristics of life were not initially present on earth. Scientists have used experimentation to determine how organisms evolved that could grow, reproduce, and maintain an internal environment.
Nuclear Power
Controlled nuclear fission reactions are used to generate electricity. Any nuclear reactor that produces power via the fission of uranium or plutonium by bombardment with neutrons has six components: nuclear fuel consisting of fissionable material, a nuclear moderator, a neutron source, control rods, reactor coolant, and a shield and containment system.
Nuclear Fuels
Nuclear fuel consists of a fissile isotope, such as uranium-235, which must be present in sufficient quantity to provide a...
Nuclear Fuels
Nuclear fuel consists of a fissile isotope, such as uranium-235, which must be present in sufficient quantity to provide a...
Nuclear Fusion
The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process called fusion. The principal source of energy in the sun is a net fusion reaction in which four hydrogen nuclei fuse and ultimately produce one helium nucleus and two positrons.
A helium nucleus has a mass that is 0.7% less than that of four hydrogen nuclei; this lost mass is converted into energy during the fusion. This reaction produces about...
A helium nucleus has a mass that is 0.7% less than that of four hydrogen nuclei; this lost mass is converted into energy during the fusion. This reaction produces about...
Conditions on Early Earth
Around 4 billion years ago, oceans began to condense on earth while volcanic eruptions released nitrogen, carbon dioxide, methane, ammonia, and hydrogen into the primordial atmosphere. However, organisms with the characteristics of life were not initially present on earth. Scientists have used experimentation to determine how organisms evolved that could grow, reproduce, and maintain an internal environment.
Radiation: Applications
The average temperature of Earth is the subject of much current discussion. Earth is in radiative contact with both the Sun and dark space; it receives almost all its energy from the radiation of the Sun and reflects some of it into outer space. Dark space is very cold, about 3 K, so Earth radiates energy into it. For instance, heat transfer occurs from soil and grasses, the rate of which can be so rapid that frost can occur on clear summer evenings, even in warm latitudes.
The average...
The average...


