A tektite

Tektites (from Greek tektos, molten) are natural glass objects, up to a few centimeters in size, which — according to most scientists — have been formed by the impact of large meteorites on Earth's surface, although a few researchers favor an origin from the Moon as volcanic ejecta. Tektite , released under GNU FDL File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... This article refers to the material. ... Artists impression of a major impact event. ... A meteorite is a small extraterrestrial body that impacts the Earths surface. ... Earth, also known as Terra, and Tellus mostly in the 19th century, is the third-closest planet to the Sun. ...

Tektite origin: two theories

The terrestrial-impact theory states that an impact melts material from the Earth's surface and catapults it up to several hundred kilometers away from the impact site. The molten material cools and solidifies to glass. According to this theory, although a meteorite impact causes the formation, the precursor material of tektites is primarily of terrestrial origin, as determined from isotopic measurements. The color of tektites is black or olive-green, and their shape varies from rounded to irregular. Terrestrial literally means of the earth and is used in a variety of contexts: In biology and in the general sense, terrestrial means indicates ground-dwelling (compare aquatic). ...

As the impact theory states, tektites cannot be found everywhere on Earth's surface. They are only found in four strewnfields, three of which are associated with known impact craters. Only the largest, geologically youngest tektite deposit in Southeast Asia, called the Australasian strewnfield, has thus far had no known impact crater associated with it. This is probably due to the fact that even very large impact structures are often not easy to detect. For example, since the Chesapeake Bay impact crater (today the largest known impact structure of the United States and associated with the North American tektite strewnfield) is covered by sediments, it was not detected until the early 1990s. Also, the bigger the strewnfield, the bigger the area to search for the crater. Since several new craters are identified every year, this is not really regarded as a problem by proponents of the impact theory, except for the purported Australasian crater, a feature that would be less than a million years old and thus easily visible. This crater, if it exists at all, has not been located. This article is about impact craters, also known as meteor craters. ... Asia is the largest and most populous of the Earths continents. ... The Chesapeake Bay Impact Crater was formed by the impact of an extraterrestrial bolide that hit about 35. ... The 1990s refers to the years 1990 to 1999; the last decade of the 20th Century, but in an economical sense The Nineties is often considered to span from the fall of the Berlin Wall in November 1989 to the September 11 attacks in 2001. ...

A moldavite tektite

The ages of tektites from the four strewnfields have been determined using radiometric dating methods. The age of moldavites, a type of tektite found in Czech Republic, was determined to be 14 million years, which agrees well with the age determined for the Nördlinger Ries crater (a few hundred kilometers away in Germany) by radiometric dating of Suevite (an impact breccia found at the crater). Similar agreements exist between tektites from the North American strewnfield and the Chesapeake Bay impact crater and between tektites from the Ivory Coast strewnfield and the Lake Bosumtwi-Crater. Image File history File links Moldavite, GNU-FDL, from Suomi Wikipedia, uploaded by user MP File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Moldavite, GNU-FDL, from Suomi Wikipedia, uploaded by user MP File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The Nördlinger Ries is a depression in western Bavaria, Germany, located north of the Danube in the district of Donau-Ries. ... Breccia, derived from the Latin word for broken, is a sedimentary rock composed of angular fragments in a matrix that may be of a similar or a different material. ...

Below are some types of tektites, grouped according to the four known strewnfields, and their associated craters:

• European strewnfield (Nördlinger Ries, Germany, age: 14 million years):
  • Moldavites (Czech Republic, green)
• Australasian strewnfield (the strewnfield covers more than 10 percent of the Earth's surface although the young, gigantic crater purportedly associated with it — which should not have eroded in so short a time — has not been located after decades of searching by impact adherents; the age of these tektites is 0.7 million years or perhaps younger):
  • Australites (Australia, dark, mostly black)
  • Indochinites (Südostasien, dark, mostly black)
  • Chinites (China, black)
• North American strewnfield (Chesapeake Bay impact crater, USA, age: 34 million years):
  • Bediasites (USA, Texas, black)
  • Georgiaites (USA, Georgia, green)
• Ivory Coast strewnfield (Lake Bosumtwi-Crater, Ghana, age: 1 million years); tektites from this event have been found as far east as Australia:
  • Ivorites (Ivory Coast, black)

Today, the terrestrial origin of tektites is accepted by many geochemical and isotopic studies (e.g. Faul H.(1966), Koeberl C.(1990)). Moldavite from Besednice, Bohemia Moldavite is an olive-green or dull greenish vitreous substance formed by a meteorite impact. ...

Earlier theories about an origin from space or from the Moon have been discarded by most scientists, but the "mainstream" theory is currently rejected by several serious students of the tektite-origin debate as examined below.

Aerodynamically shaped Australie

No cosmogenic noble gases, produced by cosmic rays, are found in tektites. This excludes a long travel in space as would be necessary if tektites are not terrestrial. This fact makes a lunar origin very unlikely, according to terrestrial-impact adherents, because it is hard to explain why, unlike in tektites, cosmogenic noble gases were found in all lunar meteorites, and a typical transfer time from Moon to Earth of about 1 million years was determined for lunar meteorites. Furthermore, an origin from Moon or space cannot explain why many tektites are only found in confined areas (although one could debate whether the Australasian and Ivory Coast tektites fit into this definition), unlike meteorites of lunar or other origin, which can be found in many places on Earth's surface. In particular, no tektite strewnfield exists in Antarctica, where the flow of glaciers helps extraterrestrial material accumulate in some places. However, the Australasian strewnfield expands with each new tektite discovered on the southern seafloor. This tektite field may yet be found to reach as far as Antarctica, but regularly undertaken meteorite recovery expeditions in areas that accumulate extraterrestrial material have found only meteorites and no tektites at all. If tektites from space fall in Antarctica, a large part of the recovered material should instead be tektites and an existing strewnfield should already have been discovered. Conversely, the Australasian and Ivory Coast strewnfields have expanded over the decades as new tektites are found in sea sediments; they now reach toward the southern continent. Thus, it may be premature for terrestrial-origin proponents to say that tektites will never be discovered on Antarctica. Image File history File links Download high resolution version (768x609, 68 KB) Description: Australite, flanged button, back side, oblique view. ... Image File history File links Download high resolution version (768x609, 68 KB) Description: Australite, flanged button, back side, oblique view. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... Lunar Meteorite Allan Hills 81005 A Lunar meteorite is a meteorite that is known to have originated on the Moon. ...

Measurements of high concentrations of the radionuclide ¹⁰Be in tektites from the relatively young Australasian strewnfield is, according to researchers, of terrestrial origin. ¹⁰Be is produced by cosmic rays in the atmosphere, where it is down-washed by rain and incorporated into young sediment layers. Because of its half-life of about 1.5 million years, ¹⁰Be decays with time and is not found in older sediments and other kinds of rocks in such high concentrations. It is found in meteorites and lunar rocks, but not in such high concentrations because the interaction of cosmic rays with these rocks produces much smaller quantities of ¹⁰Be. In particular, these findings are regarded by many as the final breakthrough for the impact theory, because they show that the precursor material is mainly of terrestrial origin (although small traces of extraterrestrial material, perhaps the impactor, are mixed in). General Name, Symbol, Number beryllium, Be, 4 Chemical series alkaline earth metals Group, Period, Block 2, 2, s Appearance white-gray metallic Atomic mass 9. ...

Conversely, in defense of the lunar-origin theory, it should be noted that scientists who claim tektite glasses are impact melts generally ignore important primary clues: their structure (petrography) and high quality. Instead, they base their claims on comparisons of tektite chemistries with the averages of certain sediments and on certain rare-earth and isotopic values they claim don't exist in the Moon. Other researchers, however, have shown that tektite glasses are not really comparable to terrestrial sediments, due to the latter's wide range of chemical variance — especially in the alkalis — and instead often exhibit igneous (volcanic) chemical trends. They also argue against the physical impossibility of forming tektites by impact "jetting" or "compression rebound".

In 1961, officials at the U.S. Air Force's Cambridge Research Laboratories in Bedford, Massaschusetts, were keenly interested in the chemical and physical characteristics of tektites. "Project 7698" was commissioned with W.H. Pinson, Jr. of the Massachusetts Institute of Technology as the principal investigator. The 7698 final report concluded that the strontium isotopic composition of tektites did not match those of terrestrial rocks and impactites. Pinson concluded the theory of formation by random fusion of terrestrial materials "whether by impact of meteorites, asteroids, comets or lightning" could not be supported.

It has been shown by researchers working on certain Apollo samples that a number of terrestrial-like rare-earth and isotopic values evidently do exist at depth in the Moon. Such samples have reached the surface in certain volcanic processes. Both terrestrial and lunar volcanism have produced iridium values comparable to that of the KT (Cretaceous/Tertiary) clay/microtektite layer. However, either terrestrial or lunar volcanism can not explain isotopic anomalism found in the KT boundary. In other words, chromium isotopic composition is homogeneous within the Earth-Moon system, so the chromium isotopic anomaly found in the KT boundary can be explained only if material from an impactor (asteroid or comet) were mixed in. Material of lunar origin, discovered to date, cannot explain the isotopic characteristics. General Name, Symbol, Number iridium, Ir, 77 Chemical series transition metals Group, Period, Block 9, 6, d Appearance silvery white Atomic mass 192. ...

NASA scientist John A. O'Keefe published numerous papers between the 1950s and 1990s discussing these lunar rare-earth, isotopic and other chemistries, and how they relate to tektite glass. John A. OKeefe (1916-2000) was a planetary scientist with the National Aeronautics and Space Administration (NASA) from 1958 to 1995. ...

Thus, some tektite researchers continue to strongly disagree with the popular terrestrial-impact theory; they suggest that tektites are more likely volcanic ejecta from the Moon.

From the 1950s through the 1990s, NASA aerodynamicist Dean R. Chapman and others advanced the "lunar origin" theory of tektites. Chapman used complex orbital computer models and extensive wind tunnel tests to support the theory that the so-called Australasian tektites originated from the Rosse ejecta ray of the large crater Tycho on the Moon's nearside. Until the Rosse ray is sampled, a lunar origin for these tektites cannot be ruled out. During the 1980s and 1990s, researchers such as O’Keefe of NASA, astronomer and long-time tektite researcher Hal Povenmire, and petrologist Darryl Futrell claimed that the slow way in which tektite glass formed (called "fining"), and the volcanic features they claimed to have observed within some layered tektites, couldn’t be explained by the terrestrial-impact theory. Unlike all terrestrial impactite glasses, tektites are nearly free of internal water similar to lunar rocks. Also, Stokes Law does not permit the formation of tektites during impact while the velocity needed to form certain "flanged" tektites is more compatible with a lunar origin rather than a terrestrial origin. O'Keefe suggested explosive, hydrogen-driven lunar volcanoes as the original source of tektites. Note: Since the unmanned U.S. Clementine lunar mission of the 1990s, vast areas of pyroclastic (volcanic) glasses have been indentified, notably in the area of the Aristarchus plateau. There is also evidence of interstitial granitic material (akin to the acidic tektites in chemistry) in some lunar highland samples which bolsters the lunar-origin theory. Lunar Orbiter spacecraft images reveal fields of volcanic domes that may indicate deep-seated, high-silica eruptions on the Moon, possible sources of the tektites. (These domes are similar to the Mono Lake craters of California; ironically, Mono obsidians resemble some layered tektites). 1950 (MCML) was a common year starting on Sunday (link will take you to calendar). ... This article is about the year. ... NASA Logo Listen to this article · (info) This audio file was created from the revision dated 2005-09-01, and does not reflect subsequent edits to the article. ... Dean R. Chapman, (1922-1995) had a distinguished engineering career spanned more than 50 years, both in government service at the National Aeronautics and Space Administration (NASA) Ames Research Center and Stanford University. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Tycho is: The first name of Tycho Brahe, a Danish nobleman, well known as an astronomer/astrologer A crater on the moon named after him; see Tycho (crater) A crater on Mars named after him; the Tycho Brahe crater A character from the webcomic Penny Arcade (comic), also named for... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... 1980 (MCMLXXX) was a leap year starting on Tuesday. ... This article is about the year. ... NASA Logo Listen to this article · (info) This audio file was created from the revision dated 2005-09-01, and does not reflect subsequent edits to the article. ... Terrestrial literally means of the earth and is used in a variety of contexts: In biology and in the general sense, terrestrial means indicates ground-dwelling (compare aquatic). ... Water (from the Old English word wæter; c. ...

A part of one of the rock samples collected on Apollo 12, lunar sample 12013, has a composition which is remarkably similar to some tektites. It is especially similar to high-magnesium javenites (part of the Australasian field). Sample 12013 is inhomogenous in that it is composed of two types of materials, light and dark. The light, acidic portion is composed of up to 71 percent silicon dioxide. The dark portion resembles KREEP rocks. The abundances of 20 of 23 elements tested from the acidic portion of the sample showed a striking similarity to high-magnesium tektites. The major elements matched well; the minor and trace elements did not. However, other lunar samples matched some microtektites very well. KREEP stands for potassium (atomic symbol K), rare earth elements (REE), and phosphorus (P). ...

Even with great similarity to a tektite, lunar sample 12013 is not generally accepted as a tektite. However, it is similar enough to some tektites that it cannot be ignored. Thus, mineralogist Brian Mason and petrologist W.G. Melson, geologists Edward Chao, Robert J. Foster, and Jack Green — along with astronomers Mark R. Chartrand, Franklyn Branley, J.E. van Zyl, Paolo Maffei and ceramic scientist David Pye — reject the terrestrial-origin theory and support a lunar origin.

Finally, according to O'Keefe and Povenmire, Apollo 14 lunar sample 14425 resembles some high-magnesium, low silica content microtektites. However, this claim was rejected in a study by scientist B.P. Glass. Regardless, O'Keefe said that "If 14425 was found in Antarctica instead Fra Mauro (on the Moon), it would probably have been accepted as a tektite."

While the more visible tektite-origin "battle" may have quieted down since the Apollo-era, it continues among some serious meteorite researchers and collectors who have studied the topic in depth and refuse to surrender their favorite theory.

Literature

Books

• Heinen, G. (1998) Tektites — Witnesses of Cosmic Catastrophes, published privately
• McCall, G.J.H. (2001) Tektites in the Geological Record The Geological Society London
• O'Keefe, J.A. (1976) Tektites and their origin. Elsevier.
• Povenmire, H. (2003)Tektites: A cosmic paradox. Florida Fireball Network

Articles

• Cameron, W. S. & Lowrey, B.E. (1975) Tektites: Volcanic ejecta from the Moon. The Moon, 31–360.
• Chapman, Dean R. (1971) Australasian tektite geographic pattern, crater and ray of origin, and theory of tektite events. Journal of Geophysical Research, Vol. 76, No. 26, 6309–6338.
• Chao, E.C.T. (1993) Comparison of the Cretaceous-Tertiary boundary impact events and the 0.77-ma Australasian tektite event... U.S.G.S. Survey Bulletin 2050, G.P.O.
• Faul H.(1966) Tektites are terrestrial. Science, Vol. 152, 1341–1345.
• Futrell, D. (February & March 1999) The lunar origin of tektites. Rock & Gem.
• Futrell, D. & Varricchio, L. (2002) An argument against the terrestrial origin of tektites. Meteorite, Vol. 8, No. 4, pp. 34–35.
• Glass, B. P. (1986) Lunar sample 14425: Not a lunar tektite, Geochimica et Cosmochimica Acta 50, 111–113.
• Koeberl C.(1990) The geochemistry of tektites: An overview. Tectonophysics Vol. 171, 405–422.
• Mason, B. & Melson, W.G. (1970) The lunar rocks. Wiley Interscience, 113–115.
• NASA Ames Research Center (Sept. 22, 1969) NASA fact sheet Tektites, tons of the Moon already on Earth.
• O'Keefe, J.A. (June 5, 1970) Tektite glass in Apollo 12 sample. Science, Vol 168, 1209–1210.
• O'Keefe, J.A. (Feb. 26, 1985) The coming revolution in planetology. Eos, Vol. 66, No. 9, pp. 89–90.
• O'Keefe, J.A. (1993)The origin of tektites.Meteoritics, Vol. 29, No. 1, pp. 73–78.

External links

Wikimedia Commons has media related to:

Tektite

• http://www.scienceagogo.com/news/20000202063509data_trunc_sys.shtml
• http://www-pat.llnl.gov/tektite/
• http://www.physicstoday.org/pt/vol-54/iss-6/p76.html
• http://www.spacedaily.com/news/deepimpact-02k.html
• http://www.meteoritetimes.com/Back_Links/2002/october/upcoming_in_meteorite.htm