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【学术报告】Redox Revolutions on Earth and Beyond

2020-10-29

报告时间2020.11.05(星期四)上午10:00-12:00AM

会议地点:天津大学地科院221报告厅

线上观看方式:1. zoom (会议号:624 2488 7929;密码:123123)  建议优先通过该方式观看报告,以便交流提问

                        2.Bilibili直播链接:https://live.bilibili.com/22606419

嘉宾:Ariel Anbar 教授

嘉宾简介:

Ariel D. Anbar毕业于加州理工大学,美国亚利桑那州立大学(ASU)地球与空间探索学院教授,国际地球化学学会会士(Fellow of the Geochemical Society)。Anbar是金属稳定同位素地球化学的先行者之一,其研究主要利用金属元素及其稳定同位素重建地球环境与生命演化、氧气与古海洋化学的演化历史、以及探索地外宜居星球等。目前已发表>150篇论文,包括多篇Science, Nature,Nature Geoscience, PNAS, Science Advances等文章,谷歌学术H-index 66,总引用近2万次,在同位素地球化学、古海洋地球化学和天体生物学领域极具影响力。Anbar在教学方法的创新方面也有非常重要的成就,开创了基于虚拟现实技术的线上教学平台,目前担任ASU Center for Education Through eXploration主任。

报告摘要:

Redox Revolutions on Earth and Beyond

 

The molecule O2 looms large in the search for life on extrasolar planets, because Earth’s O2-rich atmosphere is a consequence of biology. Commonly, it is assumed that an Earth-like planet on which oxygenic photosynthesis evolves will inevitably accumulate O2 in its atmosphere and pervasively alter the surface environment – that biological redox innovations inexorably lead to environmental redox revolutions. However, close examination of Earth’s environmental redox history challenges this assumption.

 

Increasingly, it appears that evolution of the solid Earth played a key role in modulating the oxygenation of Earth’s surface environment. Multiple lines of evidence now suggest that O2 was being produced biologically hundreds of millions of years before its accumulation in the atmosphere during the Great Oxidation Event (GOE), ca. 2.4 Ga, and hence that Earth’s surface redox revolution was substantially delayed. This delay can be accounted for by interactions between the atmosphere and the solid planet, because the biological production of O2 is ultimately balanced by consumption through reaction with reductants derived from Earth’s interior. In particular, recent examinations of oxygen fugacity during the formation of Precambrian basalts and komatiites suggest that large volumes of the mantle underwent a secular increase of oxygen fugacity through the Archean and early Proterozoic. The cause(s) of this secular shift remain unclear, but when translated into a secular evolution of the redox state of volcanic gases, the observed mantle trend can account for a shift from net O2 consumption to net O2 production at about 2.4 Ga.

 

This emerging understanding of Earth’s redox revolution raises important questions about the likelihood of similar revolutions on other worlds even in the presence of large biospheres powered by oxygenic photosynthesis. Even modest differences in mantle compositions or tectonics might substantially alter the timing of surface oxygenation. On some worlds, atmospheric O2 accumulation might be impossible. This realization highlights the need for far better understanding of solid Earth processes - and how these processes might operate on other nominally “Earth-like” worlds.

 

 

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