The Big Splash

The giant impact theory (or Big Splash or Big Whack; cf. Big Bang) 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 sometimes called Theia. The theory was first proposed in a paper published in Icarus in 1975 by Dr. William K. Hartmann and Dr. Donald R. Davis. Image File history File links Download high resolution version (401x1071, 17 KB) A sketch of the Big Splash theory of the formation of the moon. ... Image File history File links Download high resolution version (401x1071, 17 KB) A sketch of the Big Splash theory of the formation of the moon. ... cf. ... According to the Big Bang theory, the universe originated in an extremely dense and hot state (bottom). ... Theory has a number of distinct meanings, depending on the context. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... Earth, also known as the Earth, Terra, and (mostly in the 19th century) Tellus, is the third-closest planet to the Sun. ... 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. ... Theia is the hypothetical planet that, according to the giant impact theory of the Moons formation, collided with the Earth over four billion years ago. ...

4.533 billion years (4.533 Ga) ago, shortly after the formation of the Earth, a Mars-sized planetesimal hit the Earth at an oblique angle, destroying the impactor and ejecting most of that body along with a significant portion of the Earth's felsic-rich mantle out into space. Some of this material then coalesced into the Moon from an orbiting ring of debris. Current estimates based on computer simulations of such an event suggest the spherical shape of the moon was attained between only one and one hundred years after the impact. To help compare orders of magnitude of different times this page lists times between 1017 seconds and 1018 seconds (3200 million years and 32 000 million years) See also times of other orders of magnitude. ... Mega-annum, usually abbreviated as Ma, is a unit of time equal to one million years. ... In cosmogony, planetesimals are objects thought to exist within solar nebulae. ... Felsic is a term used in geology to refer to silicate minerals, magmas, and rocks which are enriched in the lighter elements, such as silica, oxygen, aluminium, sodium, and potassium. ... Earth cutaway from core to exosphere. ...

Evidence for this impact comes from rocks collected during the Apollo Moon landings, which show an oxygen isotope composition that is nearly identical to the Earth's mantle. Chemical inspection of those rocks found them to be nearly devoid of volatile and lighter elements, leading to the speculation that they formed from an unusually extreme amount of heating that boiled them off. Seismometers on the Moon have measured the size of its nickel-iron core and have found that it is much smaller than predicted under other formation scenarios, such as tandem formation with the Earth. A smaller core is consistent with the impact theory because this theory predicts that the moon was formed mostly from the mantle of the Earth and partly from the mantle of the impacting body and not from the core of the impacting body (it is thought that the core of the impactor sank and merged with the Earth's core). Description Role: Earth and Lunar Orbit Crew: 3; CDR, CM pilot, LM pilot Dimensions Height: 36. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... Isotopes are forms of an element whose nuclei have the same atomic number–-the number of protons in the nucleus--but different atomic masses because they contain different numbers of neutrons. ... Seismometer (in Greek seismos = earthquake and metero = measure) are used by seismologists to measure and record seismic waves. ... General Name, Symbol, Number nickel, Ni, 28 Chemical series transition metals Group, Period, Block 10, 4, d Appearance lustrous, metallic Atomic mass 58. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ...

Other than the existence of the Moon itself, the primary legacy of this event, say researchers, is the fact that the Earth does not have enough of the lighter-colored felsic and intermediate rock-types to completely cover its entire surface. Thus we have continents made from felsic rocks and ocean basins which are made of the darker-colored, heavier and more metal-rich mafic rock types. This difference in composition along with the presence of water allows for an extensively active system of plate tectonics on the Earth. Others have postulated that the axial-tilt and initial rotation of the Earth had their origin with the so-called giant impact. Dymaxion map by Buckminster Fuller shows land mass with minimal distortion as only one continuous continent A continent (Latin continere, to hold together) is a large continuous land mass. ... Ocean (from Okeanos, a Greek god of sea and water; Greek ωκεανός) covers almost three quarters (71%) of the surface of the Earth, and nearly half of the worlds marine waters are over 3000 m deep. ... Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily forms ions (cations) and has metallic bonds, and metals are sometimes described as a lattice of positive ions (cations) in a cloud of electrons. ... In geology, mafic minerals are silicate minerals, magmas, and volcanic and intrusive igneous rocks that have relatively high concentrations of the heavier elements. ... Water (from the Old English word wæter; c. ... Plate tectonics (from the Greek word for one who constructs, τεκτων, tekton) is a theory of geology developed to explain the phenomenon of continental drift, and is currently the theory accepted by the vast majority of scientists working in this area. ...

Animation of Theia forming in Earth's L₄ point and then drifting into impact. The animation progresses in one-year steps making Earth appear not to move, and the moon in the wrong direction.

The apparent improbability of a Mars-sized body hitting the Earth at exactly the correct angle to avoid completely destroying the planet, combined with the fortunate degree of axial-tilt that this event set up (thus allowing for seasons), and for making possible vigorous plate tectonics on the Earth (which is vital to the carbon cycle) has been put forward by some to explain the apparent rarity of life in the universe. This idea is called the Rare Earth hypothesis. However, in a recent article Edward Belbruno and Richard Gott III argue that an impact body could have formed at the Lagrangian point L₄ or L₅, and then drifted into a chaotic orbit that would impact the Earth with a suitably low velocity; this mechanism would allow for such impact events with a significantly increased probability. 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. ... A planet in common parlance is a large object in orbit around a star that is not a star itself. ... The carbon cycle is the biogeochemical cycle by which carbon is exchanged between the biosphere, geosphere, hydrosphere and atmosphere of the Earth. ... Radio telescope observations play a role in researching the Fermi paradox The Fermi paradox is a paradox proposed by physicist Enrico Fermi that questions the probability of finding intelligent extraterrestrial life. ... The deepest visible-light image of the cosmos. ... The rare Earth hypothesis is a response to the Fermi paradox which explains why we might expect a planet such as Earth to be very rare. ... The Lagrangian points (IPA: ; also Lagrange point, L-point, or libration point), are the five positions in space where a small object can be stationary with respect to two larger objects (such as a satellite with respect to the Earth and Moon). ...

Simulation work published in 2005 by Robin Canup suggested that Pluto's moon Charon could also have formed by a giant impact around 4.5 billion years ago, in this case by another Kuiper belt object between 1600 and 2000 kilometres in diameter that struck the planet at a speed of 1 kilometre per second. Canup speculated that this process of moon formation could have been common in the early solar system. Atmospheric characteristics Atmospheric pressure 0. ... Charon (shair-un or kair-un, Greek Χάρων) is the only known satellite of Pluto. ... The Kuiper belt (KYE per) is an area of the solar system extending from within the orbit of Neptune (at 30 AU) to 50 AU from the sun, at inclinations consistent with the ecliptic. ...

References

• Dana Mackenzie, The Big Splat, or How Our Moon Came to Be, 2003, John Wiley & Sons, ISBN 0-471-15057-6.

See also: 2002 in literature, other events of 2003, 2004 in literature, list of years in literature. ...

External links

• Planetary Science Institute page on the Giant Impact Theory. Hartmann and Davis belonged to the PSI. This page also contains several paintings of the impact by Hartmann himself.
• Southwest Research Institute, UCSC researchers identify the Moon-forming impact
• Computer modelling of the moon's creation
• Southwest Research Institute press release on the impact theory of the origin of Charon.