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Encyclopedia > Giant impact hypothesis
The Big Splash. View from the south pole.
The Big Splash. View from the south pole.

The giant impact hypothesis (sometimes referred to as the big whack, or, less frequently, the big splash) is the now-dominant scientific theory for the formation of the Moon, which is thought to have formed as a result of a collision between the young Earth and a Mars-sized body that is sometimes called Theia[1] or, on rare occasion, Orpheus. The name of Theia (IPA: /ˈθiːə/) is derived from Greek mythology, as Theia was the Titan who gave birth to the Moon goddess Selene. The hypothesis was first proposed at a conference on satellites in 1974 and then published in Icarus in 1975 by Drs. William K. Hartmann and Donald R. Davis. This article is about a non-fiction book. ... Image File history File links BigSplashEnglish. ... Image File history File links BigSplashEnglish. ... The word theory has a number of distinct meanings in different fields of knowledge, depending on their methodologies and the context of discussion. ... This article is about Earths moon. ... This article is about Earth as a planet. ... Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ... For other uses, see Orpheus (disambiguation). ... The bust of Zeus found at Otricoli (Sala Rotonda, Museo Pio-Clementino, Vatican) Greek mythology is the body of stories belonging to the Ancient Greeks concerning their gods and heroes, the nature of the world and the origins and significance of their own cult and ritual practices. ... In Greek mythology, Theia (also written Thea or Thia), also called Euryphaessa (wide-shining), was a Titan. ... This article is about the race of Titans in Greek mythology. ... This article is about the lunar spacecraft. ... ICARUS is the official journal of the Division for Planetary Sciences of the American Astronomical Society. ... Dr. William K. Hartmann is a noted planetary scientist, author, and writer, and is currently a senior scientist at the Planetary Science Institute. ...

Contents

Origins

One hypothesis is that Theia formed at a Lagrangian point relative to Earth, that is, in about the same orbit and about 60° ahead or behind.[2] When the protoplanet Theia had grown to about the size of Mars, it became too massive to reside stably in a Trojan orbit. As a result, its angular distance from Earth fluctuated, with the fluctuations growing larger until it hit the Earth. This is calculated to have occurred 4.533 billion years ago (4.533 Ga); Theia is thought to have struck the Earth at an oblique angle, destroying Theia and ejecting most of Theia's mantle and a significant portion of the Earth's mantle into space, while Theia's core sank into Earth's core. Current estimates based on computer simulations of such an event suggest that some two percent of the original mass of Theia ended up as an orbiting ring of debris, about half of which coalesced into the Moon between one and 100 years after the impact. Regardless of the rotation and inclination the Earth had before the impact, after the impact it would have had a day some five hours long, and the Earth's equator would have shifted closer to the plane of the Moon's orbit. A contour plot of the effective potential (the Hills Surfaces) of a two-body system (the Sun and Earth here), showing the five Lagrange points. ... Protoplanets are moon-sized planet embryos within protoplanetary discs. ... Adjectives: Martian Atmosphere Surface pressure: 0. ... As originally defined, Trojan asteroids have a semi-major axis between 5. ... Annum is a Latin noun meaning year. ... Earth cutaway from core to exosphere. ... Earth cutaway from core to exosphere. ... It has been suggested that simulation software be merged into this article or section. ... This article is about Earths moon. ...


Evidence

Indirect evidence for this impact scenario comes from rocks collected during the Apollo Moon landings, which show oxygen isotope compositions that are nearly the same as the Earth. The highly anorthositic composition of the lunar crust, as well as the existence of KREEP-rich samples, gave rise to the idea that a large portion of the Moon was once molten, and a giant impact scenario could easily have supplied the energy needed to form such a magma ocean. Several lines of evidence show that, if the Moon has an iron-rich core, it must be small. In particular, the mean density, moment of inertia, rotational signature, and magnetic induction response all suggest that the radius of the core is less than about 25% the radius of the Moon, in comparison to about 50% for most of the other terrestrial bodies. Impact conditions can be found that give rise to a Moon that formed mostly from the mantles of the Earth and impactor, with the core of the impactor accreting to the Earth, and which satisfy the angular momentum constraints of the Earth-Moon system.[3] Apollo Program insignia Project Apollo was a series of human spaceflight missions undertaken by the United States of America using the Apollo spacecraft and Saturn launch vehicle, conducted during the years 1961–1972. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) pale blue (liquid) Standard atomic weight 15. ... For other uses, see Isotope (disambiguation). ... Lunar Ferroan Anorthosite #60025 (Plagioclase Feldspar). ... KREEP stands for potassium (atomic symbol K), rare earth elements (REE), and phosphorus (P). ... This article, which relates to the Moon, is a stub. ... For other uses, see Iron (disambiguation). ...


A belt of warm dust in a zone between 0.25AU and 2AU from the young star HD 23514 in the Pleiades cluster appears similar to the predicted results of Theia's collision with the embryonic Earth, and has been interpreted as the result of planet-sized objects colliding with each other.[4] This is similar to another belt of warm dust detected around the star BD+20 307 (HIP 8920, SAO 75016).[5] Pleiades refers to: Pleiades (star cluster) an open cluster of stars in the constellation Taurus. ...

Animation of Theia forming in Earth's L5 point and then drifting into impact. The animation progresses in one-year steps (before impact) making Earth appear not to move. The view is of the south pole.
Animation of Theia forming in Earth's L5 point and then drifting into impact. The animation progresses in one-year steps (before impact) making Earth appear not to move. The view is of the south pole.

Image File history File links Download high resolution version (620x620, 304 KB) Big Slash V1. ... Image File history File links Download high resolution version (620x620, 304 KB) Big Slash V1. ...

Difficulties

Even the dominant lunar origin theory has some difficulties which have yet to be explained. These difficulties include:

  • Ratios of the Moon's volatile elements are not consistent with the giant impact hypothesis.[6]
  • There is no evidence that the Earth ever had a magma ocean (an implied result of the giant impact hypothesis), and some material was found which may never have been in a magma ocean. [6]
  • Iron oxide (FeO) content of 13% of the bulk Moon properties rule out the derivation of the proto-lunar material from any but a small fraction of Earth's mantle.[7]
  • If the bulk of the proto-lunar material had come from the impactor, the Moon should be enriched in siderophilic elements, when it is actually deficient of those.[8]
  • Certain simulations of the formation of the Moon require about twice the amount of angular momentum that the Earth-Moon system has now. However, these simulations do not take into consideration Earth's rotation before impact. Some researchers consider this as insufficient evidence for disregarding the giant impactor theory.[9][10]

The Goldschmidt Classification, developed by Victor Goldschmidt, is a geochemical classification which groups the chemical elements according to their preferred host phases into siderophile (iron loving), lithophile (silicate loving), chalcophile (sulphur loving), and atmophile (gas loving). ...

See also

This article is about Earths moon. ... Exploring Shorty crater during the Apollo 17 mission to the Moon. ... KREEP stands for potassium (atomic symbol K), rare earth elements (REE), and phosphorus (P). ... The Roche limit (pronounced ), sometimes referred to as the Roche radius, is the distance within which a celestial body, held together only by its own gravity, will disintegrate due to a second celestial bodys tidal forces exceeding the first bodys gravitational self-attraction. ...

References

Cited references

  1. ^ U. Wiechert, A. N. Halliday, D.-C. Lee, G. A. Snyder, L. A. Taylor, D. Rumble (October 2001). "Science" 294 (12): 345-348. [1]
  2. ^ Belbruno, E.; J. Richard Gott III (2005). "Where Did The Moon Come From?". The Astronomical Journal 129 (3): 1724-1745. arXiv:astro-ph/0405372. 
  3. ^ R. Canup and E. Asphaug (2001). "Origin of the Moon in a giant impact near the end of the Earth's formation". Nature 412: 708-712. 
  4. ^ Rhee, Joseph H.; Inseok Song, B. Zuckerman (2007). "Warm dust in the terrestrial planet zone of a sun-like Pleiad: collisions between planetary embryos?". ApJ. arXiv:astro-ph/0711.2111v1. 
  5. ^ Song, Inseok; B. Zuckerman, Alycia J. Weinberger and E. E. Becklin (21 July 2005). "Extreme collisions between planetesimals as the origin of warm dust around a Sun-like star". Nature 436: 363-365. doi:10.1038/nature03853. 
  6. ^ a b Tests of the Giant Impact Hypothesis, J. H. Jones, Lunar and Planetary Science, Origin of the Earth and Moon Conference, 1998 [2]. Note: The source notes evidence that suggests there might never have been a global magma ocean, but the source doesn't explicitly rule out the existence of a magma ocean, either.
  7. ^ The Bulk Composition of the Moon, Stuart R. Taylor, Lunar and Planetary Science, 1997, [3]
  8. ^ E. M. Galimov and A. M. Krivtsov (December 2005). "Origin of the Earth-Moon System". J. Earth Syst. Sci. 114 (6): 593-600.  [4]
  9. ^ Canup, Robin (Spring 1999). Big Bang, New Moon. Technology Today. Southwest Research Institute. Retrieved on 2007-07-25.
  10. ^ Taylor, G. Jeffrey (December 31, 1998). Origin of the Earth and Moon. Planetary Science Research Discoveries (PSRD). Hawaii Institute of Geophysics & Planetology. Retrieved on 2007-07-25.

Scientific references arXiv (pronounced archive, as if the X were the Greek letter χ) is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and quantitative biology which can be accessed via the Internet. ... arXiv (pronounced archive, as if the X were the Greek letter χ) is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and quantitative biology which can be accessed via the Internet. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Southwest Research Institute (SwRI) is an independent, nonprofit applied research and development organization. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 206th day of the year (207th in leap years) in the Gregorian calendar. ... is the 365th day of the year (366th in leap years) in the Gregorian calendar. ... Year 1998 (MCMXCVIII) was a common year starting on Thursday (link will display full 1998 Gregorian calendar). ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 206th day of the year (207th in leap years) in the Gregorian calendar. ...

General references Dr. William K. Hartmann is a noted planetary scientist, author, and writer, and is currently a senior scientist at the Planetary Science Institute. ... IAU redirects here. ... Cornell redirects here. ... For other uses, see Icarus (disambiguation). ... Alastair G. W. (Graham Walter) Cameron, (1925-2005) was a Canadian astrophysicist and space scientist who was an eminent staff member of the Astronomy department of Harvard University. ... The American Geophysical Union (or AGU) is a nonprofit organization of geophysicists, consisting (as of 2006) of over 49,000 members from over 140 countries. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... March 10 is the 69th day of the year (70th in leap years) in the Gregorian calendar. ... The University of Arizona Press is a publishing house and a department of the University of Arizona in Tucson, Arizona that engages in academic publishing. ...

John Wiley & Sons, Inc. ... is the 365th day of the year (366th in leap years) in the Gregorian calendar. ... Year 1998 (MCMXCVIII) was a common year starting on Thursday (link will display full 1998 Gregorian calendar). ...

External links


This article is about Earths moon. ... For other uses, see Calendar (disambiguation) A page from the Hindu calendar 1871–1872. ... Look up Month in Wiktionary, the free dictionary. ... This article is about the Moon as the subject of and inspiration for creative works. ... The Moon has figured in many mythologies, often paired or contrasted with the Sun (see also Solar deity). ... The Moon illusion is an optical illusion in which the Moon appears larger near the horizon than it does while higher up in the sky. ... The lunar effect is the supposed influence of the moon, and its various phases, on human behaviour. ... The orbit of the Moon around the Earth is completed in approximately 27. ... Lunar phase refers to the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. ... Photo taken during the 1999 eclipse. ... Time lapse movie of the 3 March 2007 lunar eclipse A lunar eclipse occurs whenever the Moon passes through some portion of the Earths shadow. ... This article is about tides in the Earths oceans. ... Schematic illustration of the internal structure of the Moon. ... Radial gravitational anomaly at the surface of the Moon. ... Topography of the Moon, referenced to the lunar geoid. ... Total magnetic field strength at the surface of the Moon as derived from the Lunar Prospector electron reflectometer experiment. ... The atmosphere of the Moon is very tenuous and insignificant in comparison to that of the Earth. ... Selenography is the study of the surface and physical features of the Moon, especially the mapping of the features according to the Moons latitude and longitude. ... The near side of the Moon is the lunar hemisphere that is permanently turned towards the Earth, and as such the side which is always seen. ... Far side of the Moon. ... The Lunar maria (singular: mare, IPA: //) are large, dark, basaltic plains on Earths Moon, formed by ancient volcanic eruptions. ... Tycho crater on Earths moon. ... The South Pole-Aitken basin is an impact crater on Earths Moon. ... Shackleton is a lunar crater that lies at the south pole of the Moon. ... The continuous bombardment of the Moon by comets and meteoroids have added some amount of water to the lunar surface. ... Peak of Eternal Light (PEL) describes a point on a body within the solar system which is eternally bathed in sunlight. ... Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ... This map, based on a survey of 300 TLPs by Barbara Middlehurst and Patrick Moore, shows the approximate distribution of observed events. ... Exploring Shorty crater during the Apollo 17 mission to the Moon. ... The lunar geologic timescale (or perhaps more properly the selenologic timescale) divides the history of Earths Moon into six generally recognized geologic periods: Copernician Period : 1100 MY to present Eratosthenian Period : 3200 MY to 1100 MY Upper Imbrian Epoch : 3800 MY to 3200 MY Lower Imbrian Epoch : 3850 MY... Lunar Ferroan Anorthosite #60025 (Plagioclase Feldspar). ... Lunar Meteorite Allan Hills 81005 A Lunar meteorite is a meteorite that is known to have originated on the Moon. ... KREEP stands for potassium (atomic symbol K), rare earth elements (REE), and phosphorus (P). ... The Apollo Lunar Surface Experiment Package, or ALSEP, was a set of connected scientific instruments left on the Moon when the Apollo program ended. ... The Lunar Laser Ranging Experiment from the Apollo 11 mission The ongoing Lunar Laser Ranging Experiment measures the distance between the Earth and the Moon using laser ranging. ... The Late Heavy Bombardment (LHB) was a period approximately 3. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Project Apollo was a series of human spaceflight missions undertaken by the United States of America (NASA) using the Apollo spacecraft and Saturn launch vehicle, conducted during the years 1961 – 1975. ... Pioneer 0 (USA, 1958) - failure - orbiter Pioneer 1 (USA, 1958) - failure - orbiter Pioneer 3 (USA, 1958) - failure - flyby Luna 1 (Soviet Union, 1959) - success - flyby Pioneer 4 (USA, 1959) - partial success - flyby Luna 2 (Soviet Union, 1959) - success - impactor Luna 3 (Soviet Union, 1959) - success - flyby Ranger 3 (USA, 1962... It has been suggested that this article or section be merged into Exploration of the Moon. ... “Lunar outpost” redirects here. ... Buzz Aldrin and Neil Armstrong in NASAs training mockup of the Moon and lander module. ... This article is about the Solar System. ... A natural satellite is an object that orbits a planet or other body larger than itself and which is not man-made. ...


  Results from FactBites:
 
Impact event - Wikipedia, the free encyclopedia (2903 words)
Impact events are caused by the collision of large meteoroids, asteroids or comets (generically: bolides) with Earth and may sometimes be followed by mass extinctions of life.
It was not until 1903–1905 that the Barringer Crater was correctly identified as being an impact crater, and it was not until as recently as 1963 that research by Eugene Merle Shoemaker conclusively proved this hypothesis.
This has led to the suggestion that the Chicxulub impact was one of several that occurred almost simultaneously, perhaps due to a disrupted comet impacting the Earth in a similar manner to the collision of Comet Shoemaker-Levy 9 with Jupiter in 1994.
  More results at FactBites »

 
 

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