By their low density and low entry angle, the meteoroids from the streams of defunct comets could deceased elliptical scars, shallow ponds that currently are silted worldwide.
The shallowness of these ponds are still under the influence of the geology, type of soil and the topography, as wel the climate, the water and wind erosion, the fauts in the surface where they are located. Moreover, the social demands conducting busbars or drain, the angle of fall of the meteoroid and the power of explosion, or the mass of the meteoroids, all of this can form fields of an unexpected scars configuration.
The elliptical shape of palaeolagoons is associated with the low angle of fall and the displacement of the meteor shock wave on the ground, before the final explosion of the impact forming the deepest region of the pond.
The formation of these elliptical structures is also associated with the Earth's gravity, the drag of the elliptical cloud of debrites on the ground.
Comets nucleus, made of dirty ice of low density, its fragments would escavate only a very shalow crater. A number of physical and chemical consequences of the comet impact are wortly of investigation. It is interest to discover whether cometary molecular species, such as CO2, CO, and HCN, could survive the explosion.
The synthesis of new molecular species in the cooling fireball may be of interest, as well as the production of high-temperature species such as CN, HCN, and nitrogen oxides by passage of the shock front through the Earth´s atmosphere must also be considered.
After the atomic power airblast and ground explosion of billions of meteors, in this semiarid region of Brazil with shallow, stony, and often crystalline rocks outcrop soil, thousands of depressions were formed on the ground. These structures were filled after the subsequents rains, forming lagoons where none existed before. But filled of mortal cyanits acid poisoned water.
So many elliptical ponds...
Some local groups of scars, elliptical ponds, have a same parallel orientation. They may have formed in the same event. On the other hand, many groups have convergent orientation, or divergent. This feature can be explained by the local time (LT) of the event occurrence, or the height of the meteors shower radiant in the sky.
Imagine four (4) simultaneous meteoritic events, at the same universal time (UT), in opposite sides of the globe. Divided into two (2) entent groups, one couple on South America (X,Z) and another couple on the South Asian (X´, Z´). Although the group of events occurred at the same universal time (UT), they occurred in different local time (LT).
When planning the globe's surface, we find that the trajectories appear to have convergent angles, although we know that their trajectories are parallel.
This means that setting the orientation of the palaeolagoons, the elliptical ponds, they may be associated with local time of the cosmic event, if they are originated from the same meteoroid stream, albeit at different local times (LT).
A similar effect, but divergent, is observed in relation to meteor showers, they appear to originate from a small region of the sky, from the radiant. However please note that this is only an effect of observer's perspective.
A meteor shower duration could be short as 2 days long, like Ursids, to a 40 days Taurids or Aquarids, Ophiunchids is a 25 days long. On average, one week is the most common! Thus, the Earth as it approached a torus of meteoroids can traverse an orbit of meetings, lasting from 2 to 40 days. And travel from 5 to 100 million kilometers into the torus of meteoroids from defuncts comets.
The meteoroids of toroid orbit around the Sun in parallel orbits. Each meteoroid has its own orbit, and reach the Earth as parallel meteors.
The inner toroidal chaotic distribution of the meteoroid stream that reaches the ground can form multiple events and groups of palaeolagoons with quite different aspects, from a single elliptical pond or square lagoons in a range of impacts, still, to a more abstract groupings, amoeboid when they are modified by water in the last thousand years. The palaeolagoons can have a dozen or hundreds of meters, to a dozen kilometer size. Often they are very shallow.
Many astronomers believe that there is long-term fifteen or thirty million year cycle to impacts as the result of galactic tides affecting comets in the Oort cloud believed to surround the solar system like a halo. In 1982, two British astronomers, S. V. M (Victor) Clube and William Napier, published a book entitled The Cosmic Serpent. Clube and Napier suggested that the outer planets occasionally divert giant comets (more than 50 kilometers in diameter) into the inner solar system into short-period orbits. Debris from the resultant disintegration of these giant comets can adversely affect the environment of the Earth. Dusting can block sunlight, resulting in globally cooler conditions. Impact events in the super-Tunguska class may result in not only heavy localized destruction but also the occasional "impact winter" or dust veil with global climatological effects.
The astronomers believe the impact flux varies on an even shorter cycle. They suggest that a giant comet (over fifty kilometers in diameter) arrives in the inner solar system every hundred thousand years on average. As the giant comet disintegrates, its debris may threaten the Earth with a greatly enhanced impact flux for a few years or decades every millenium or two.
The theoretical and observational evidence that, on timescales relevant to mankind, the prime collision hazard is posed by temporally correlated impacts (coherent catastrophism, t ~ 10 2 10 4 yr) rather than random ones (stochastic catastrophism, t ~ 10 5 10 8 yr). The mechanism whereby coherent incursions into and through the terrestrial atmosphere occur is described as being the result of giant cometary bodies arriving in orbits with perihelia in the inner solar system. The relative importance of active and inactive comets in the cratering record, pointing out the potentially significant contribution by disintegrating large comets to the population of inactive Earth-crossers.
NEW - 2012
Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago
Impact events in the Super-Tunguska class may result in not only heavy localized destruction but also the occasional "impact winter" or dust veil with global climatological effects. Clube and Napier identify the progenitor of the Taurid complex as such a giant comet whose injection into a short-period (about 3.3 year) orbit occurred sometime in the last twenty thousand years. The effects of the disintegration of this object in an Earth-crossing orbit should appear in the geological and climatological record as well as in protohistorical and historical records.
The observed thousands of scars, craters, the Palaeolagoons should represent real marcs of these prehistorical cosmic events. The scars are found in Brazil and everywhere throughout the world. A cosmic massive global event may have last a few hours to some days long. Millions of meteoroids explosions and airblast fired forests and cause tsunami at seas and oceans, incinerating the lands and prehistoric villages, melting glaciers, and poisoning the waters with their hot CN rich plasma jets. The excess of warm in the atmosphere and oceans released large bodies of unfrozen water during the end of Pleistocene, changing all the ecosystems, initiating a new environmental order, the Holocene.
In 2004 during a scientific mission, Italian and Bazilian scientists investigated the Quarí palaeolagoon in São Raimundo Nonato, in Piauí, Brazil, and conducted a sediment lagoon profile. The group identified five (5) units of sediments (U.S.). The US-3: is a Silliceous clasts rocks layer, and it could be 12,900 BP old sedment.
The US-3 clasts layer are not vulcanic, and they are possible impactites.
The Quarí palaeolagoon is the result of range of low density meteoroid impacts around the year 12,900 BP. Many others ponds in the region could have a more recent (or older) origin, from a low millennial frequency events, but as well cosmic, from the fragments of a big comet (> 50 km diameter), or perhaps from a stray Kuiper planetoid.
Excavation (2011) on German small ponds structures gave evidence that high temperatures in the form of intense melting and glass formation: matrix-rich breccia - multicolored small rock fragments in a sandy, silty black matrix, can be found on small structures.
Some crateriform small structures from ten meters in diameters in young sediments in Southeast Germany have raised increased interest in the last decade, although they have been known since longtime. Its possible anthropogenic origin or simple sink holes origin were excluded, detailed rock-magnetic studies point to new ideas focusing on a formation of at least part of the craters are meteorite craters originating from the recently proposed large Holocene so-called Chiemgau impact event.
Most impactites found in impact craters is a type of "breccia".
The impactites are metamorphic rocks of the impact site formed during the cosmogenic process. Therefore, they have varied appearances, depending on the types of rocks from the impact site, temperature and pressure of the ionized gases of the shock wave on the target.
The impactite research
New publication on cosmogenic palaeolagoons
Agrupación Astronómica de La Safor
Boletin Huygens n. 94 - Enero/Febrero - 2012