Tektites are natural black, brown or olive-green glass believed to have been formed by the impact of a large meteorite on Earth'Â’s surface. Great heat and pressures were required. The 'dryness' of all tektites suggests that they were formed or at least, solidified, in outer space where there is no air nor water. Some facts of tektites support this theory while other new and intriguing findings suggest other possibilities.
Tektites: Glass Meteorites from Outer Space
It used to be thought that tektites were ‘from the moon’ but this theory has been more-or-less ruled improbable. Between the 1950s and 1990s it was theorized by NASA specialists that tektites were impact ejecta from a prominent lunar impact site called the Rosse formation, on the near-side and brilliant lunar crater Tycho.
While more facts about tektites have made this unlikely, the lunar-impact theory is not entire ruled out.
Remaining was the second major theory; the meteorite impact theory which has its own merits and problems. Both theories speak to the fact that tektites were formed ‘in outer space.’ That much is not in doubt.
Tektites are unusual for any Earth material, noted for their glassiness and ‘dryness,’ their lack of water. The average water content for tektites is something like 0.005%, far drier than most indigenous Earth rocks. Nearly all craters where tektites are found were actually formed below water while the actual material is super-dry?
Even Earth rocks formed both above and below water have more water content in their makeup than do tektites. This speaks to the theory that the material came from above, from outer space.
Tektites Show Signs of Travel Though the Earth's Atmosphere
(image source, author’s personal collection of tektites)
The meteorite impact theory implies that the impact ejects molten terrestrial material into space hundreds of miles high. This is where it gets drier than any Earth-based process can manage. The ejecta material loses nearly all traces of water while molten and in the low orbit of outer space.
Eventually, this re-solidified material falls back to Earth and by the friction of traveling through the atmosphere at nealy 25-kilometers per second, re-melts. The molten material takes on characteristic shapes of atmospheric ablation (‘melting’.) One of the major tenants of the meteor impact theory is that tektites are not found dispersed evenly around the globe but only in very specific locations called ‘strewnfields.’
Strewnfields are created when a larger space rock breaks up on high-speed entry through the atmosphere (called ‘mid-air fragmentation’) and they strike the ground over a very specific (generally elliptical) area called ‘fragmentation strewn fields’ and along a path trajectory.
‘Impact strewn fields’ are created when the meteorite breaks-apart on impact, causing the strewnfield to be more round in shape. Impact strewn fields don't provide much evidence of trajectory of the missile prior to impact, merely that there was an impact.
Known meteorites from the moon found on Earth while quite rare, have been found more-or-less dispersed everywhere on the Earth including the Antarctic. To date, no tektites of any sort have been found in the Antarctic, just meteorites and of all known types.
This zero-tektites anomaly favors the localized meteoric impact model for tektites although the Australasia strewnfield is being extended southward with every new find. Perhaps someday soon, tektites will be found in the Antarctic which will factor into the modeling of new or augment existing theories.
Tektites are found in just four places on Earth (the European strewnfield, the Australasian strewnfield, the North American and Ivory Coast strewnfields, each with several minor sub-strewn fields associated with craters near each of the larger namesakes.) Three of these major strewnfields are related to known major impact crater sites. Only the Australasian strewnfield has not as yet been associated with an impact crater. It probably exists, it is just buried and still undiscovered.
These localization sites of tektites favor the ‘meteor-Earth impact’ theory and not so much the ‘trans-lunar capture-impact’ model. Other factors which include isotopic analysis of tektites also tend to rule out the lunar theory as well, but it is not completely discounted.
New discoveries might yet reveal that at least some tektites may in fact be lunar captures from material ejected by larger meteoric impacts on the moon.
Many tektites often have elongated and/or ‘teardrop’ shapes, suggesting a ‘line-of-transit’ fall to Earth before solidifying. Some very special tektites have the quintessential ablative shell (image above) that it more typical for meteorites (both stony and iron specimens) that do not ‘tumble’ during entry through Earth atmosphere.
Corning Museum of Glass (Corning, NY) Tektite Collection
Enter a New Theory of Tektites Formation
The Journal of Royal Astronomical Society of Canada in 2004 has offered a new and intriguing theory (ppg.192;) that the material of tektites is in fact from a ‘ring system’ that orbited Earth much like Saturn’s rings do today. This was probably formed by a near-miss collision of a large space body with Earth, a grazing-collision that torn a large chink from Earth and sent it into orbit. This is also congruent with a current model of how the moon was formed.
The decaying orbit of this low ‘ring system’ eventually brought all of the re-solidified 'ring material' into the atmosphere where it fell, remelting in the atmosphere to form glassy tektites. The 'ring' consisted of both Earthly and extra-terrestrial materials. Here again, the bubbly and often ablative shapes of tektites speak to the fact that they fell in a molten state from space above. So we are still left with the standing theory that tektites are from outer space, even if just barely. If Earth ever had a ‘Saturn-like’ ring system, it entirely fell back into Earth millions of years ago which also speaks to the known age of tektites.