Science fiction writers have proposed that mankind may some day engage in Terraforming planets in the solar system or universe. The concept envisions a massive technological undertaking to extract water and oxygen from the natural resources on the planet, creating a habitable troposphere and hydrosphere . We propose that the Earth’s environment was enhanced during a series of naturally occurring cometary impact events over the last 15,000 years, effectively terraforming the earth and fostering the growth of human civilization.

Circumstantial evidence exists suggesting the earth has been struck repeatedly in the recent era by extraterrestrial bodies. The Taurid Complex has been proposed as the source of these impacts . Anecdotal evidence in the form of legends, mythology and historical religious texts present human eyewitness accounts of the earth in global chaos during several periods. More recently, the period from 500 AD to 1000 AD, collectively known as the “Dark Ages”, has generated seemingly unjustifiable accounts of environmental disruption. (See The Anglo-Saxon Chronicles in the Enigma discussions). The specific year 536AD has been proposed by others as a date of a possible impact 1. However, the lack of physical evidence in the form of impact crater structures and debris fields has rendered the celestial impact theories moot and indefensible as mainstream science. Clube an Napier 2 suggest that substantial disruption could be created by Tunguska-type cometary airbursts and dust veil events, while Dallas Abbott and the Holocene Impact Working Group posit that deep-water ocean impacts and attendant tsunamis have left identifiable evidence in the past 10,000 years 3.

Among potential impactors crossing earth’s orbit are a class of cometary or cometary derivative objects exhibiting characteristics of low density and high water content. We propose that the generally-applied model for planetary impact crater formation associated with metallic or rocky impactor does not apply directly to impacts by these bodies. Specifically, we postulate that in the specialized case of shallow angle of incidence earth impacts by large hydrated comets, a fluid dynamics-based model would apply instead.

The Taurid Complex is a cometary debris stream revolving around the Sun in an earth-crossing orbit. Analysis suggests that during the recent past, a significant mass has been removed from the Taurid progenitor 4. We propose the earth captured this missing mass into earth orbit as large (~100+ km diameter.) cometary fragments, during several close Earth-Taurid orbit intersections over the past 15,000 years. The resulting earth satellite orbits would be highly elliptical, eventually decaying such that the captured comet bodies would make contact with the earth’s surface during a grazing interface at perigee. The concept is introduced as Perigee: Zero, or PZ. We propose that after one or more grazing events the cometary body, reduced in size and having lost momentum, would dissipate in a terminal impact.

The PZ cometary bodies are hydrated silica; effectively “dirty snowballs”. Due to the water content and shearing angle, crater structures are cleanly excised from sedimentary layers as a hydraulic action, resulting in geologic structures not traditionally identified with impact.

PZ-Grazing events manifest themselves as "bruises" in which the passing comet body removes all flora and fauna along with unconsolidated soils. PZ-Trenching is used to describe the “trenching” action as a comet body slashes across the terrain during an intersecting perigee, where the width is constrained by the diameter of the comet body. PZ-Terminal events are very low angle-of-incidence impacts materialized as fan-shaped distributions of ejecta as the body is fully disrupted. PZ-Airburst event, which would result in airbursts similar to the Tunguska event of 1918, are not identified or evaluated. Similarly, on orbits immediately prior to the actual PZ-Grazing events, “near-miss” atmospheric transit events would have occurred. We suggest this caused significant environmental damage, but have not attempted identification of them. Using remote sensing imaging, we examine approximately 50 landforms meeting the criteria.

We demonstrate that PZ Ejecta material is ballistically distributed over significant distances from the impact site in the form of tsunamite splash, lofted droplets and intact strata of varying masses and water/mineral ratios. PZ Tsunamite and PZ Splash ejecta is cleanly excised from sedimentary layers and consists of slurry of pulverized and hydrated minerals (sand, clay, mineral) and impactor elements. In several cases examined, ejecta are manifested as geographically repositioned intact or folded terrestrial stratum, from undercutting and lofting. We will refer to this as PZ Divot ejecta. Significantly, in each case, the resulting geologic landforms are not traditionally recognized as ejecta structures.

Visual evidence in the form of remote sensor imaging of PZ craters and of the correlated PZ-Ejecta landforms is presented. Further correlation is attempted using the location, composition and geomorphology of the anomalous ejecta emplacements and their immediate surroundings. Observed sequential accretion of ejecta layers is discussed.

This discussion is limited to the manifestations of damage to above-sea-level terrestrial surfaces and sea areas of less than 1 kilometer deep. An observed "terminal" cratering count of 25 is seen as representing the manifestations of perhaps 20 cometary bodies. The oceans represent much higher percentage of surface area. When adjusted upward to account for oceanic impacts, we propose that 30 cometary bodies may have accreted from the Taurid stream.

The advancement of human civilization is considered by some to have been fostered by the development of agriculture and the associated change from hunter-gatherer existence. This change may have been supported by the dramatic stabilization of the earth’s environment that provides the demarcation between the Pleistocene and the Holocene eras. An alternative could be that a significant percentage of the Earth’s hydrosphere was delivered during the PZ impact series. PZ ejecta emplacements are often manifested as water-retaining structures, and may represent a significant percentage of today’s natural fresh water lakes. Together these two are seen as changing the ratio of land-to-water surface area, enhancing the energy distribution of meteorological processes and providing the observed stabilization of the earth’s temperature during the Holocene.

The British historian Arnold Toynbee proposed his theory of challenge and response in A Study of History (1934-1961). Toynbee believed that civilizations arise only where the environment challenges the people, and only when the people are ready to respond to the challenge. For example, a hot, dry climate makes land unsuitable for farming and represents a challenge to people who live there. The people may respond to this challenge by building irrigation systems to improve the land. Toynbee suggested that civilizations collapse when the people lose their creativity. 5

Throughout the treatise, we attempt to provide correlation to evidence of human observation and comment, be it oral, written or artistic. We have identified several works of art which are interpreted being actual documentation of the Taurid Complex stream of cometary bodies as seen from the earth during transits through the stream. In each of these instances, what we interpret to be graphic representations of comets are documented, first at an initial count of bodies, then at a reduced count, with the "missing" members shown in a different context. These are discussed in the Comet Physics Observation Maps section.

Timing of the entire Perigee: Zero sequence is discussed in the companion Timeline section.

1 A comet impact in AD5 36?, E Rigby, Cardiff University, M Symonds and D Ward-Thompson, Astronomy and Geophysics, February 2004 Vol 45

2 The Cosmic Serpent by Victor Clube and Bill Napier ISBN 0-87663-379-3 299 pages. 1982 Review

3 Paper in development. Review by S. Blakeslee, Ancient Crash, Epic Wave, NY Times 11-14-2006

4 The structure and evolution of the Taurid complex (Royal Astronomical Society, Monthly Notices (ISSN 0035-8711), vol. 251, Aug. 15, 1991, p. 632-648.).

The British historian Arnold Toynbee. "////," The World Book Multimedia Encyclopedia, World Book, Inc., 2001.