偉大な酸化イベントの前に酸素の匂いがする?
Ariel D Anbar1, Yun Duan, Timothy W Lyons
1School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA. anbar@asu.edu
Science (New York, N.Y.)
|September 29, 2007
まとめ
初期の地球の海は,古代のシェールでモリブデンとレニウムの濃縮によって示された,グレート酸化イベントの5000万年以上前に酸素を含んでいた. これは,初期の大気中の酸素を示唆し,アーケアの環境についての私たちの理解に影響を与えています.
科学分野:
- 地質化学 地質化学
- パレオセアノグラフィー
- 初期の地球の条件.
背景:
- 大酸化イベント (GOE) は,大気中の酸素の有意な上昇を記した.
- GOE以前の環境条件は完全に理解されていません.
- レドックスに敏感な金属は,古代の海洋化学の代理として機能することができます.
研究 の 目的:
- アルケア後期マウント・マクレイ・シェールにおける酸化還元反応に敏感な金属の存在を調査する.
- 金属の濃縮の起源とタイミングを決定する.
- 初期の地球の大気中の酸素レベルへの影響を評価する.
主な方法:
- 金属の濃度を分析するための高解像度ケモストラトグラフィー.
- 金属の源を推測するために,有機炭素との相関.
- レニウム/オスミウムのジオクロノロジーは,堆積物の特徴を年代測定する.
主要な成果:
- モリブデンとレニウムの濃縮がマウント・マクレイ・シェールで発見された.
- 金属の濃縮は有機炭素と相関しており,海水の起源を示しています.
- レーニウム/オスミウムの年代測定では,濃縮が2501 +/- 800万年前に起こったとされています.
- 証拠によると,金属は硫化物の酸化気象によって供給されたという.
結論:
- マウント・マクレイ・シェイルの記録では,海水から金属を濃縮した初期のエピソードが記録されています.
- この濃縮は,グレート・オキシデーション・イベントの5千万年以上前のものです.
- 発見は,アルカイア後期の環境で局所的な酸素の存在を示しています.
関連する概念動画
01:26Origin of Photosynthesis
Photosynthesis represents a fundamental biological process that transformed Earth's atmosphere and paved the way for complex life. Emerging roughly 3.4–3.8 billion years ago, the earliest photosynthetic organisms harnessed light energy to produce organic compounds. These anoxygenic phototrophs used electron donors like hydrogen sulfide (H₂S) or ferrous iron (Fe²⁺), rather than water, and did not release molecular oxygen (O₂) as a byproduct. Various groups, including green sulfur and purple...
01:26Oxygenic Photosynthesis
Oxygenic photosynthesis is a fundamental process in which light energy is harnessed to drive the oxidation of water, leading to the production of molecular oxygen (O₂), adenosine triphosphate (ATP), and nicotinamide adenine dinucleotide phosphate (NADPH). This process is essential for sustaining aerobic life on Earth and is primarily carried out by cyanobacteria, algae, and plants. The core of oxygenic photosynthesis lies in the thylakoid membranes, where chlorophyll pigments facilitate light...
01:20Gas Exchange and Transport
Gas exchange, the intake of molecular oxygen (O2) from the environment and the outflow of carbon dioxide (CO2) into the environment, is necessary for cellular function. Gas exchange during respiration occurs largely via the movement of gas molecules along pressure gradients. Gas travels from areas of higher partial pressure to areas of lower partial pressure. In mammals, gas exchange occurs in the alveoli of the lungs, which are adjacent to capillaries and share a membrane with them.
01:27Oxygen Transport in the Blood
Hemoglobin (Hb) is a crucial molecule in the human body, consisting of four polypeptide chains, each bound to an iron-containing heme group. This unique structure enables hemoglobin to bind to oxygen, with each molecule capable of combining with four molecules of oxygen, leading to rapid and reversible oxygen loading. When fully loaded with oxygen, it is called oxyhemoglobin, while hemoglobin that has released oxygen is called reduced hemoglobin or deoxyhemoglobin. As hemoglobin binds oxygen,...
01:46Oxidative Cleavage of Alkenes: Ozonolysis
In ozonolysis, ozone is used to cleave a carbon–carbon double bond to form aldehydes and ketones, or carboxylic acids, depending on the work-up.
Ozone is a symmetrical bent molecule stabilized by a resonance structure.
Ozone is a symmetrical bent molecule stabilized by a resonance structure.
01:20Radical Autoxidation
The oxidation of an organic compound in the presence of air or oxygen is called autoxidation. For example, cumene reacts with oxygen to form hydroperoxide. Autoxidation involves initiation, propagation, and termination steps. Many organic compounds are susceptible to autoxidation—especially ethers in the presence of oxygen, which form hydroperoxides. Even though this reaction is slow, old ether bottles contain small amounts of peroxide, which leads to laboratory explosions during ether...