Early Earth

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Early Earth is loosely defined as Earth in its first one billion years, or gigayear (Ga, 109y). [1] Early Earth is defined as encompassing approximately the first gigayear in the evolution of the planet from its initial formation in the young Solar System at about 4.55 Ga to sometime in the Archean eon in approximately 3.5 Ga. [2] On the geologic time scale, this comprises all of the Hadean eon, starting with the formation of the Earth about 4.6 billion years ago, [3] and the Eoarchean, starting 4 billion years ago, and part of the Paleoarchean era, starting 3.6 billion years ago, of the Archean eon.

Contents

This period of Earth's history involved the planet's formation from the solar nebula via a process known as accretion. This time period included intense meteorite bombardment as well as giant impacts, including the Moon-forming impact, which resulted in a series of magma oceans and episodes of core formation. [4] After formation of the core, delivery of meteoritic or cometary material in a "late veneer" may have delivered water and other volatile compounds to the Earth. [5] Although little crustal material from this period survives, the oldest dated specimen is a zircon mineral of 4.404 ± 0.008 Ga enclosed in a metamorphosed sandstone conglomerate in the Jack Hills of the Narryer Gneiss Terrane of Western Australia. [6] The earliest supracrustals (such as the Isua greenstone belt) date from the latter half of this period, about 3.8 gya, around the same time as peak Late Heavy Bombardment.

History

According to evidence from radiometric dating and other sources, Earth formed about 4.54 billion years ago. [7] [8] [9] The current dominant theory of planet formation suggests that planets such as Earth form in about 50 to 100 million years but more recently proposed alternative processes and timescales have stimulated ongoing debate in the planetary science community. [10] For example, in June 2023, one team of scientists reported evidence that Earth may have formed in just three million years. [11] [10] Nonetheless, within the first billion years of the formation of Earth, [12] [13] [14] [15] life appeared in its oceans and began to affect its atmosphere and surface, promoting the proliferation of aerobic as well as anaerobic organisms. Since then, the combination of Earth's distance from the Sun, its physical properties and its geological history have allowed life to emerge, develop photosynthesis, and, later, evolve further and thrive. The earliest life on Earth arose at least 3.5 billion years ago. [16] [17] [18] Earlier possible evidence of life includes graphite, which may have a biogenic origin, in 3.7-billion-year-old metasedimentary rocks discovered in southwestern Greenland [19] and 4.1-billion-year-old zircon grains in Western Australia. [20] [21]

In November 2020, an international team of scientists reported studies suggesting that the primeval atmosphere of the early Earth was very different from the conditions used in the Miller–Urey studies considering the origin of life on Earth. [22]

See also

Related Research Articles

The timeline of the evolutionary history of life represents the current scientific theory outlining the major events during the development of life on planet Earth. Dates in this article are consensus estimates based on scientific evidence, mainly fossils.

The Precambrian is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic Eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time.

<span class="mw-page-title-main">Age of Earth</span> Scientific dating of the age of Earth

The age of Earth is estimated to be 4.54 ± 0.05 billion years (4.54 × 109 years ± 1%). This age may represent the age of Earth's accretion, or core formation, or of the material from which Earth formed. This dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial material and lunar samples.

The Hadean is the first and oldest of the four known geologic eons of Earth's history, starting with the planet's formation about 4.54 Bya, now defined as Mya set by the age of the oldest solid material in the Solar System found in some meteorites about 4.567 billion years old. The supposed interplanetary collision that created the Moon occurred early in this eon. The Hadean ended 4.031 billion years ago and was succeeded by the Archean eon, with the Late Heavy Bombardment hypothesized to have occurred at the Hadean-Archean boundary.

<span class="mw-page-title-main">Proterozoic</span> Geologic eon, 2500–539 million years ago

The Proterozoic is the third of the four geologic eons of Earth's history, spanning the time interval from 2500 to 538.8 Mya, the longest eon of the Earth's geologic time scale. It is preceded by the Archean and followed by the Phanerozoic, and is the most recent part of the Precambrian "supereon".

<span class="mw-page-title-main">Archean</span> Geologic eon, 4031–2500 million years ago

The Archean Eon, in older sources sometimes called the Archaeozoic, is the second of the four geologic eons of Earth's history, preceded by the Hadean Eon and followed by the Proterozoic. The Archean represents the time period from 4,031 to 2,500 Ma. The Late Heavy Bombardment is hypothesized to overlap with the beginning of the Archean. The Huronian glaciation occurred at the end of the eon.

<span class="mw-page-title-main">Eoarchean</span> First era of the Archean Eon

The Eoarchean is the first era of the Archean Eon of the geologic record. It spans 431 million years, from the end of the Hadean Eon 4031 Mya to the start of the Paleoarchean Era 3600 Mya. The beginnings of life on Earth have been dated to this era and evidence of archaea and cyanobacteria date to 3500 Mya, comparatively shortly after the Eoarchean. At that time, the atmosphere was without oxygen and the pressure values ranged from 10 to 100 bar.

<span class="mw-page-title-main">Neoarchean</span> Fourth era of the Archean Eon

The Neoarchean is the last geologic era in the Archean Eon that spans from 2800 to 2500 million years ago—the period being defined chronometrically and not referencing a specific level in a rock section on Earth. The era is marked by major developments in complex life and continental formation.

<span class="mw-page-title-main">History of Earth</span> Development of planet Earth from its formation to the present day

The history of Earth concerns the development of planet Earth from its formation to the present day. Nearly all branches of natural science have contributed to understanding of the main events of Earth's past, characterized by constant geological change and biological evolution.

<span class="mw-page-title-main">Jack Hills</span> Range of hills in Western Australia

The Jack Hills are a range of hills in Mid West Western Australia. They are best known as the source of the oldest material of terrestrial origin found to date: Hadean zircons that formed around 4.404 billion years ago. These zircons have enabled deeper research into the conditions on Earth in the Hadean eon. In 2015, "remains of biotic life" were found in 4.1 billion-year-old rocks there. According to one of the researchers, "If life arose relatively quickly on Earth ...then it could be common in the universe."

<span class="mw-page-title-main">Oldest dated rocks</span> Includes rocks over 4 billion years old from the Hadean Eon

The oldest dated rocks formed on Earth, as an aggregate of minerals that have not been subsequently broken down by erosion or melted, are more than 4 billion years old, formed during the Hadean Eon of Earth's geological history. Meteorites that were formed in other planetary systems can pre-date Earth. Particles from the Murchison meteorite were dated in January 2020 to be 7 billion years old.

<span class="mw-page-title-main">Isua Greenstone Belt</span> Archean greenstone belt in southwestern Greenland

The Isua Greenstone Belt is an Archean greenstone belt in southwestern Greenland, aged between 3.7 and 3.8 billion years. The belt contains variably metamorphosed mafic volcanic and sedimentary rocks, and is the largest exposure of Eoarchaean supracrustal rocks on Earth. Due to its age and low metamorphic grade relative to many Eoarchaean rocks, the Isua Greenstone Belt has become a focus for investigations on the emergence of life and the style of tectonics that operated on the early Earth.

Biotic material or biological derived material is any material that originates from living organisms. Most such materials contain carbon and are capable of decay.

<span class="mw-page-title-main">Pilbara Craton</span> Old and stable part of the continental lithosphere located in Pilbara, Western Australia

The Pilbara Craton is an old and stable part of the continental lithosphere located in the Pilbara region of Western Australia.

<span class="mw-page-title-main">Late Heavy Bombardment</span> Hypothesized astronomical event

The Late Heavy Bombardment (LHB), or lunar cataclysm, is a hypothesized astronomical event thought to have occurred approximately 4.1 to 3.8 billion years (Ga) ago, at a time corresponding to the Neohadean and Eoarchean eras on Earth. According to the hypothesis, during this interval, a disproportionately large number of asteroids and comets collided into the terrestrial planets and their natural satellites of the inner Solar System, including Mercury, Venus, Earth and Mars. These came from both post-accretion and planetary instability-driven populations of impactors. Although it used to be widely accepted, it remained difficult to provide an overwhelming amount of evidence for the hypothesis. However, recent re-appraisal of the cosmo-chemical constraints indicates that there was likely no late spike in the bombardment rate.

<span class="mw-page-title-main">Archean life in the Barberton Greenstone Belt</span> Some of the most widely accepted fossil evidence for Archean life

The Barberton Greenstone Belt of eastern South Africa contains some of the most widely accepted fossil evidence for Archean life. These cell-sized prokaryote fossils are seen in the Barberton fossil record in rocks as old as 3.5 billion years. The Barberton Greenstone Belt is an excellent place to study the Archean Earth due to exposed sedimentary and metasedimentary rocks.

The Chaotian is a proposed time division of the geologic time scale. First proposed in 2010 as an eon, it is named after Chaos, the primeval void in Greek mythology. This proposal defines the Chaotian eon as a Solar System-wide time between the initiation of planetary formation and the hypothesised collision of the trojan dwarf planet Theia with the proto-Earth.

<span class="mw-page-title-main">Earliest known life forms</span> Putative fossilized microorganisms found near hydrothermal vents

The earliest known life forms on Earth may be as old as 4.1 billion years old according to biologically fractionated graphite inside a single zircon grain in the Jack Hills range of Australia. The earliest evidence of life found in a stratigraphic unit, not just a single mineral grain, is the 3.7 Ga metasedimentary rocks containing graphite from the Isua Supracrustal Belt in Greenland. The earliest direct known life on land may be stromatolites which have been found in 3.480-billion-year-old geyserite uncovered in the Dresser Formation of the Pilbara Craton of Western Australia. Various microfossils of microorganisms have been found in 3.4 Ga rocks, including 3.465-billion-year-old Apex chert rocks from the same Australian craton region, and in 3.42 Ga hydrothermal vent precipitates from Barberton, South Africa. Much later in the geologic record, likely starting in 1.73 Ga, preserved molecular compounds of biologic origin are indicative of aerobic life. Therefore, the earliest time for the origin of life on Earth is at least 3.5 billion years ago, possibly as early as 4.1 billion years ago — not long after the oceans formed 4.5 billion years ago and after the formation of the Earth 4.54 billion years ago.

<span class="mw-page-title-main">Eastern Block of the North China Craton</span>

The Eastern Block of the North China Craton is one of the Earth's oldest pieces of continent. It is separated from the Western Block by the Trans-North China Orogen. It is situated in northeastern China and North Korea. The Block contains rock exposures older than 2.5 billion years. It serves as an ideal place to study how the crust was formed in the past and the related tectonic settings.

<span class="mw-page-title-main">Prebiotic atmosphere</span>

The prebiotic atmosphere is the second atmosphere present on Earth before today's biotic, oxygen-rich third atmosphere, and after the first atmosphere of Earth's formation. The formation of the Earth, roughly 4.5 billion years ago, involved multiple collisions and coalescence of planetary embryos. This was followed by a <100 million year period on Earth where a magma ocean was present, the atmosphere was mainly steam, and surface temperatures reached up to 8,000 K (14,000 °F). Earth's surface then cooled and the atmosphere stabilized, establishing the prebiotic atmosphere. The environmental conditions during this time period were quite different from today: the Sun was ~30% dimmer overall yet brighter at ultraviolet and x-ray wavelengths, there was a liquid ocean, it is unknown if there were continents but oceanic islands were likely, Earth's interior chemistry was different, and there was a larger flux of impactors hitting Earth's surface.

References

  1. ↑ Rankama, Kalervo (May 1967). "Megayear and Gigayear: Two Units of Geological Time". Nature. 214 (5088): 634. Bibcode:1967Natur.214..634R. doi: 10.1038/214634a0 . ISSN   1476-4687.
  2. ↑ Vaclav Cilek, ed. (2009). "Early Earth". Earth System: History and Natural Variability Volume I. Eolss Publishers. p. 98. ISBN   978-1-84826-104-4.
  3. ↑ "International Chronostratigraphic Chart 2015" (PDF). ICS. Retrieved 23 January 2016.
  4. ↑ Carlson, Richard W.; Garnero, Edward; Harrison, T. Mark; Li, Jie; Manga, Michael; McDonough, William F.; Mukhopadhyay, Sujoy; Romanowicz, Barbara; Rubie, David (2014-01-01). "How Did Early Earth Become Our Modern World?". Annual Review of Earth and Planetary Sciences. 42 (1): 151–178. Bibcode:2014AREPS..42..151C. doi: 10.1146/annurev-earth-060313-055016 .
  5. ↑ Drake, Michael J.; Righter, Kevin (2002-03-07). "Determining the composition of the Earth". Nature. 416 (6876): 39–44. Bibcode:2002Natur.416...39D. doi:10.1038/416039a. ISSN   0028-0836. PMID   11882886. S2CID   4380038.
  6. ↑ Wilde, Simon A.; Valley, John W.; Peck, William H.; Graham, Colin M. (2001-01-11). "Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago : Abstract : Nature". Nature. 409 (6817): 175–178. Bibcode:2001Natur.409..175W. doi:10.1038/35051550. ISSN   0028-0836. PMID   11196637. S2CID   4319774.
  7. ↑ "Age of the Earth". U.S. Geological Survey. 1997. Archived from the original on 23 December 2005. Retrieved 2006-01-10.
  8. ↑ Dalrymple, G. Brent (2001). "The age of the Earth in the twentieth century: a problem (mostly) solved". Special Publications, Geological Society of London. 190 (1): 205–221. Bibcode:2001GSLSP.190..205D. doi:10.1144/GSL.SP.2001.190.01.14. S2CID   130092094.
  9. ↑ Manhesa, Gérard; Allègre, Claude J.; Dupréa, Bernard & Hamelin, Bruno (1980). "Lead isotope study of basic-ultrabasic layered complexes: Speculations about the age of the earth and primitive mantle characteristics". Earth and Planetary Science Letters . 47 (3): 370–382. Bibcode:1980E&PSL..47..370M. doi:10.1016/0012-821X(80)90024-2.
  10. 1 2 Onyett, Isaac J.; et al. (14 June 2023). "Silicon isotope constraints on terrestrial planet accretion". Nature : 1–6. doi:10.1038/s41586-023-06135-z. PMC   10356600 . PMID   37316662. S2CID   259161680. Archived from the original on 17 June 2023. Retrieved 17 June 2023.
  11. ↑ Patel, Kasha (16 June 2023). "Scientists have a controversial theory for how — and how fast — Earth formed". The Washington Post . Archived from the original on 17 June 2023. Retrieved 17 June 2023.
  12. ↑ Dalrymple, G.B. (1991). The Age of the Earth. California: Stanford University Press. ISBN   978-0-8047-1569-0.
  13. ↑ Newman, William L. (2007-07-09). "Age of the Earth". Publications Services, USGS. Retrieved 2007-09-20.
  14. ↑ Dalrymple, G. Brent (2001). "The age of the Earth in the twentieth century: a problem (mostly) solved". Geological Society, London, Special Publications. 190 (1): 205–21. Bibcode:2001GSLSP.190..205D. doi:10.1144/GSL.SP.2001.190.01.14. S2CID   130092094 . Retrieved 2007-09-20.
  15. ↑ Stassen, Chris (2005-09-10). "The Age of the Earth". TalkOrigins Archive . Retrieved 2008-12-30.
  16. ↑ Schopf, JW, Kudryavtsev, AB, Czaja, AD, and Tripathi, AB. (2007). Evidence of Archean life: Stromatolites and microfossils. Precambrian Research 158:141–155.
  17. ↑ Schopf, JW (2006). Fossil evidence of Archaean life. Philos Trans R Soc Lond B Biol Sci 29;361(1470) 869-85.
  18. ↑ Hamilton Raven, Peter; Brooks Johnson, George (2002). Biology . McGraw-Hill Education. p.  68. ISBN   978-0-07-112261-0 . Retrieved 7 July 2013.
  19. ↑ Ohtomo, Yoko; Kakegawa, Takeshi; Ishida, Akizumi; et al. (January 2014). "Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks". Nature Geoscience . 7 (1): 25–28. Bibcode:2014NatGe...7...25O. doi:10.1038/ngeo2025. ISSN   1752-0894.
  20. ↑ Borenstein, Seth (19 October 2015). "Hints of life on what was thought to be desolate early Earth". Excite . Yonkers, NY: Mindspark Interactive Network. Associated Press . Retrieved 2015-10-20.
  21. ↑ Bell, Elizabeth A.; Boehnike, Patrick; Harrison, T. Mark; et al. (19 October 2015). "Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon" (PDF). Proc. Natl. Acad. Sci. U.S.A. 112 (47): 14518–21. Bibcode:2015PNAS..11214518B. doi: 10.1073/pnas.1517557112 . ISSN   1091-6490. PMC   4664351 . PMID   26483481 . Retrieved 2015-10-20. Early edition, published online before print.
  22. ↑ Zurich, Eth (29 November 2020). "Uncovering Mysteries of Earth's Primeval Atmosphere 4.5 Billion Years Ago and the Emergence of Life" . Retrieved 30 November 2020.
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