The snowball Earth hypothesis: testing the limits of global change

Terra Nova, Journal Year: 2002, Volume and Issue: 14(3), P. 129 - 155

Published: June 1, 2002

The gradual discovery that late Neoproterozoic ice sheets extended to sea level near the equator poses a palaeoenvironmental conundrum. Was Earth's orbital obliquity > 60° (making tropics colder than poles) for 4.0 billion years following lunar‐forming impact, or did climate cool globally some reason point at which runaway ice‐albedo feedback created `snowball' Earth? high‐obliquity hypothesis does not account major features of glacial record such as abrupt onsets and terminations discrete events, their close association with large (> 10‰) negative δ 13 C shifts in seawater proxies, deposition strange carbonate layers (`cap carbonates') during post‐glacial sea‐level rise, return sedimentary iron formations, after 1.1 year hiatus, exclusively events. A snowball event, on other hand, should begin end abruptly, particularly lower latitudes. It last millions years, because outgassing must amass an intense greenhouse order overcome albedo. largely ice‐covered ocean become anoxic reduced be widely transported solution precipitated formation wherever oxygenic photosynthesis occurred, upon deglaciation. ensures transient regime enhanced silicate weathering, drive flux alkalinity could quantitatively world‐wide occurrence cap carbonates. resulting high rates sedimentation, coupled kinetic isotope effect transferring CO 2 burden ocean, down seawater, is observed. If carbonates are `smoke' Earth, what was `gun'? In proposing original Earth hypothesis, Joe Kirschvink postulated unusual preponderance land masses middle low latitudes, consistent palaeomagnetic evidence, set stage events by raising planetary Others had pointed out weathering would most likely if many continents were tropics, atmospheric climate. Negative 10–20‰ precede glaciation regions, giving rise speculation destabilized growing dependency methane, stemming ultimately from same continental distribution. Given existing palaeomagnetic, geochemical geological evidence climatic shocks without parallel Phanerozoic, it seems inevitable history life impacted, perhaps profoundly so.

Language: Английский

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Proterozoic Ocean Chemistry and Evolution: A Bioinorganic Bridge?

Science, Journal Year: 2002, Volume and Issue: 297(5584), P. 1137 - 1142

Published: Aug. 16, 2002

Recent data imply that for much of the Proterozoic Eon (2500 to 543 million years ago), Earth's oceans were moderately oxic at surface and sulfidic depth. Under these conditions, biologically important trace metals would have been scarce in most marine environments, potentially restricting nitrogen cycle, affecting primary productivity, limiting ecological distribution eukaryotic algae. Oceanic redox conditions their bioinorganic consequences may thus help explain observed patterns evolution.

Language: Английский

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Excited-State Properties of C₆₀ Fullerene Derivatives

Accounts of Chemical Research, Journal Year: 2000, Volume and Issue: 33(10), P. 695 - 703

Published: July 21, 2000

This Account reviews our main achievements in the field of excited-state properties fullerene derivatives. The photosensitizing and electron-acceptor features some relevant classes functionalized materials are highlighted, considering impact functionalization on characteristics. In addition, unique optimization terms redox potentials, water-solubility, singlet oxygen generation is presented for several novel fullerene-based materials.

Language: Английский

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THE EARLY HISTORY OF ATMOSPHERIC OXYGEN: Homage to Robert M. Garrels

Annual Review of Earth and Planetary Sciences, Journal Year: 2005, Volume and Issue: 33(1), P. 1 - 36

Published: Feb. 11, 2005

▪ Abstract This paper reviews the Precambrian history of atmospheric oxygen, beginning with a brief discussion possible nature and magnitude life before evolution oxygenic photosynthesis. is followed by summary various lines evidence constraining oxygen levels through time, resulting in suggested concentrations. Also reviewed are processes regulating concentrations, several models presented. A sparse geologic record, combined uncertainties as to its interpretation, yields only fragmentary imprecise reading evolution. Nevertheless, have increased but not monotonically, major fascinating swings both lower higher levels.

Language: Английский

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The habitat and nature of early life

Nature, Journal Year: 2001, Volume and Issue: 409(6823), P. 1083 - 1091

Published: Feb. 1, 2001

Language: Английский

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Volcanic gases, black smokers, and the great oxidation event

Geochimica et Cosmochimica Acta, Journal Year: 2002, Volume and Issue: 66(21), P. 3811 - 3826

Published: Oct. 28, 2002

Language: Английский

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Ferruginous Conditions Dominated Later Neoproterozoic Deep-Water Chemistry

Science, Journal Year: 2008, Volume and Issue: 321(5891), P. 949 - 952

Published: July 18, 2008

Earth's surface chemical environment has evolved from an early anoxic condition to the oxic state we have today. Transitional between earlier Proterozoic world with widespread deep-water anoxia and a Phanerozoic large oxygen-utilizing animals, Neoproterozoic Era [1000 542 million years ago (Ma)] plays key role in this history. The details of Earth oxygenation, however, remain unclear. We report that through much later (<742 +/- 6 Ma), remained beneath mixed layer oceans; deeper water masses were sometimes sulfidic but mainly Fe2+-enriched. These ferruginous conditions marked return ocean chemistry not seen for more than one billion

Language: Английский

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Evolution of Photosynthesis

Annual Review of Plant Biology, Journal Year: 2011, Volume and Issue: 62(1), P. 515 - 548

Published: March 3, 2011

Energy conversion of sunlight by photosynthetic organisms has changed Earth and life on it. Photosynthesis arose early in Earth's history, the earliest forms were almost certainly anoxygenic (non-oxygen evolving). The invention oxygenic photosynthesis subsequent rise atmospheric oxygen approximately 2.4 billion years ago revolutionized energetic enzymatic fundamentals life. repercussions this revolution are manifested novel biosynthetic pathways cofactors modification electron carriers, pigments, existing alternative modes carbon fixation. evolutionary history is further complicated lateral gene transfer that involved components as well endosymbiotic events. An expanding wealth genetic information, together with biochemical, biophysical, physiological data, reveals a mosaic features. In combination, these data provide an increasingly robust framework to formulate evaluate hypotheses concerning origin evolution photosynthesis.

Language: Английский

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Iron‐sulphur clusters and the problem with oxygen

Molecular Microbiology, Journal Year: 2006, Volume and Issue: 59(4), P. 1073 - 1082

Published: Jan. 9, 2006

Summary During the first billion years of life on Earth, environment was anaerobic. Iron and sulphur were plentiful, they recruited in formation iron‐sulphur (Fe‐S) clusters within ancient proteins. These provided many enzymes with ability to transfer electrons; others offered a cationic feature that tightly bound oxyanionic nitrogenous metabolites. Still acquired crystallizing surface around which polypeptide could fold establish three‐dimensional structure. However, subsequent oxygenation Earth's atmosphere by photosynthetic organisms created threat cluster‐dependent proteins still has not been fully resolved. By oxidizing environmental iron, oxygen limits its bioavailability, requiring employ complex schemes satisfy their iron requirement. More directly, species convert exposed Fe‐S unstable forms quickly decompose. Some microbes responded this dilemma retreating anaerobic habitats. Others abandoned use low‐potential electron‐transfer pathways, rely upon least stable cluster enzymes, developed antioxidant strategies protect remainder. adjustments only partially successful: largely because reliance clusters, aerobes remain vulnerable restriction oxidative stress, features higher exploit defending themselves against bacterial pathogens. Thus, history is an unusual one profoundly shaped contemporary microbial ecology.

Language: Английский

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Biogeochemistry of Sulfur Isotopes

Reviews in Mineralogy and Geochemistry, Journal Year: 2001, Volume and Issue: 43(1), P. 607 - 636

Published: Jan. 1, 2001

Research Article| January 01, 2001 Biogeochemistry of Sulfur Isotopes D. E. Canfield Danish Center for Earth System Science (DCESS) and Institute Biology, Odense University, SDU, Campusvej 55, 5230 M, Denmark Search other works by this author on: GSW Google Scholar Reviews in Mineralogy Geochemistry (2001) 43 (1): 607–636. https://doi.org/10.2138/gsrmg.43.1.607 Article history first online: 09 Mar 2017 Cite View This Citation Add to Manager Share Icon Facebook Twitter LinkedIn MailTo Tools Get Permissions Site Canfield; Isotopes. 2001;; doi: Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Dropdown Menu input auto suggest filter your All ContentBy SocietyReviews Advanced Sulfur, with an atomic weight 32.06, has four stable isotopes. By far the most abundant is 32S, representing around 95% total sulfur on Earth. The next isotope 34S, followed 33S, finally 36S least contributing only 0.0136% (Table 11). natural abundances isotopes, however, vary from these values as a result biological inorganic reactions involving chemical transformation compounds. For thermodynamic reasons, relative abundance isotopes can between coexisting phases. This... You do not have access content, please speak institutional administrator if you feel should access.

Language: Английский

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