Asteroids, Comets and Meteoroids are all relatively small objects that inhabit our Solar System. When any of them have orbits that intersect with that of the Earth they are known as Near Earth Objects or NEOs. Asteroids (a word coined by William Herschel [1738-1822]) used to be known as minor planets while meteoroids is the name applied to asteroids that are less than 50 metres in diameter, although some use 10 metres as the classification threshold.
Meteorites have had a history of being considered divine in origin, leading to different levels of veneration in various cultures(v). In the 2nd century, Clement of Alexandria is said to have concluded that “the worship of such stones to have been the first, and earliest idolatry, in the world.”
What is probably the first recorded death from a meteorite strike took place in India in February 2016(z).
Comets, until recently, were generally thought to be composed of just dust and ice, ‘dirty snowballs’, which have orbits that periodically bring them close to the sun at which stage the interaction of the comet’s dust trail with the solar wind produces a highly visible coma or tail. The nucleus can have a diameter of a couple of kilometres.
The chemical composition of comets is now known to be varied and much more complex than previously believed. In 2015, Comet Lovejoy was ejecting the equivalent of “500 bottles of wine every second” when it was closest to the sun, in the form of ethyl alcohol(w). A close encounter with the Earth would have been interesting!
In 1883 a large comet is estimated to have come within a few hundred miles of Earth. It was photographed and some years later the image was hailed as the first image of an UFO!
In recent years comets have come to been seen as potentially more dangerous than asteroids in the event of a collision. This view was graphically demonstrated when the Levy-Shoemaker comet crashed spectacularly into Jupiter in 1994, after breaking up into as many as 21 large pieces before impacting. This comet was originally about 20 km in diameter.
In 1752, the French astronomer, Pierre-Louis Moreau de Maupertuis, expressed the view that “However dangerous might be the shock of a comet, it might be so slight, that it would only do damage at the part of the Earth where it actually struck” and with coincidental foresight added “ Perhaps we should be very surprised to find that the debris of these masses that we despised were formed of gold and diamonds” considering how Richard Firestone and his associates more recently used the existence of nanodiamonds to confirm the cometary impact of 11,000 BC over North America.
Asteroids and comets have blamed for the demise of Atlantis since the end of the 18th century. It was the Italian polymath, Giovanni Rinaldo Carli, who in 1788 declared that part of a passing comet hit the Earth and was responsible for the destruction of Atlantis. A century later in his second book on Atlantis, Ignatius Donnelly similarly claimed that a comet’s collision was the cause of Atlantis’ destruction. Comets rather than asteroids were initially blamed because of their high visibility. However, as our technology advanced and we gradually became aware of the number of large asteroids that intersect with the Earth’s orbit they replaced comets as the more likely cause of historical impacts.
The early part of the 20th century saw the eccentric William Comyns Beaumontand the mysterious Hans Schlindler Bellamy both supporting the idea of Atlantis being destroyed by an encounter with an extraterrestrial object. The theory has been adopted by a growing number of popular modern writers such as Otto Muck, Egerton Sykes, Andrew Collins, Paul Dunbavin, Karl Jürgen Hepke(a), Frank Joseph explains[102.108] how a number of scholars encouraged by Muck, came forward to publicly state their belief that Atlantis had been destroyed by an extraterrestrial impact or impacts: “They included the world’s foremost authority on Halley’s Comet, Dr. M.M. Kamienski, a member of the Polish Academy of Sciences; Professor N. Bonev, one of the 20th century’s leading astronomers at the University of Sofia, in Bulgaria; and Jack Hills, of the prestigious Los Alamos National Laboratory”.
Emilio Spedicato of the University of Bergamo has written(b) and lectured widely on his hypothesis that the last Ice Age was started by an extraterrestrial impact over a continent and ended with a similar event over an ocean. This second impact was the cause of Atlantis’ destruction and Spedicato specifies Hispaniola as containing the location of its capital.
Spedicato is not alone in believing that impacts by large objects have been responsible for the triggering of past Ice Ages. As we have seen a large number of writers have suggested an impact with the Earth as the primary or at least the secondary cause of the destruction of Atlantis(d). These cosmic collisions have occurred throughout the history of our planet, continuing to this day. Most of the impact material is small and burns up in the atmosphere. Some low-density objects have penetrated the atmosphere, but disintegrated before actually impacting, generating powerful shock waves commensurate with their size. Such an event was the well know Tunguska(i)explosion over that area of Siberia in 1908. Two similar explosions occurred over South America in the 1930’s. However, some are large enough to survive the journey to the surface. Depending on the size, density, speed and angle of approach, the consequences of a large impact are difficult for the average person to appreciate. As Austen Atkinson wrote “A single impact by a rock the size of (London’s) Millennium Dome could devastate the surface of the globe with an explosive release of energy five times more powerful than the entire world’s nuclear arsenal. On 19 May 1996, just such an object came within 280,000 miles of Earth: six hours from collision. Humankind could have been eradicated.”
The most famous impact is probably that which in the Yucatan took place 66 million years ago and wiped out the dinosaurs. 11 million years later another impact in the Atlantic is credited with the expansion of the mammals according to a new study by co-author, Dennis Kent from Rutgers University.
An online calculator of impact effects was developed by scientists at Purdue University and Imperial College, London was first published in 2004 and recently updated(g).
By 2009 175 large impact craters have been discovered all over our planet, many more are undiscovered having been destroyed over time by wind and water erosion or hidden by vegetation. In 2006, a crater with a diameter of 30 km was discovered in the Southern Egyptian desert. This discovery may solve a mystery in the same region that has baffled science for over seventy years, namely, the Libyan desert glass that covers an area 60 x 100 km. However, the largest known impact crater is the Vredefort crater in South Africa with a diameter of 300 km (186 miles). But this may have to take second place to the 300 mile wide crater identified in Hudson Bay in North America.
The spectacular collision of Comet Shoemaker-Levy with Jupiter in July 1994 and the manner in which it disintegrated into a number of huge pieces before impacting over seven days, may offer one possible explanation for the mechanism that could produce the apparent clustering of 3rd millennium BC impacts on Earth.
The current estimate is that there are more than 2,000 asteroids exceeding a kilometre in size together with 10,000 over half a kilometre plus millions of smaller items in Earth-crossing orbits; collectively known as ‘Apollo objects‘. The meteor that exploded over central Russia in February 2013 belonged to this Apollo group. Add to this the risk from comets, normally larger than asteroids, and it is obvious that large-scale impacts are inevitable, however infrequent. The good news is that in 2011 it was reported that a NASA space telescope recorded a 40% reduction in their earlier calculation(j) which should be compared with the assessment referred to(f) at the end of the last paragraph of this entry. May 2012 saw further estimates being published(l).
Terminology, definitions and number estimates are constantly changing. Asteroids that are in excess of 100m across with orbits that that come within 7.5 million km of Earth are now referred to as PHAs (Potentially Hazardous Asteroids). As of June 2014 the IAU has listed 1,466 PHAs, while NASA estimates put the actual total in excess of 4,700(q).
As recently as 1953 an asteroid impact with the Moon was photographed as a flash and only in 2002 was the resulting 2Km- wide crater identified. The estimated energy released by this 300 metre wide object on impact would have been half a Megaton of TNT (35 times the Hiroshima bomb). A hit of this magnitude on Earth could have wiped out a large city.
It must be kept in mind that the immediate damage caused by actual impact itself is only the beginning of the story; tsunamis, volcanic eruptions, earthquakes together with worldwide long-term dust veils could trigger climate change leading to ongoing adverse effects on vegetation and animal life. For humans this meant death, destruction, floods, repeated crop failures and probably a breakdown in any existing civil order.
It was as recent as the 1930’s that geologists were being told that Meteor Crater in the Arizona desert was the only known evidence that an impact, with worldwide consequences, had ever taken place. It was also in the 1930’s that the first of the Apollo objects were identified. Since then, the number of large identifiable impact craters grew to hundreds and the number of Apollo objects, whose impact would have global implications, became thousands. It then became obvious that the Earth as we know it is at serious risk. World authorities are slowly realising that the probability of similar impacts in the future are simply inevitable.
Until recently, statistical analysis indicates a major impact every 10,000 years; with the last such event occurred 12,000 years ago possibly destroying Atlantis, directly or indirectly. However, in 2006, this estimate was revised downward to a major collision every 1,000 years with the last impact having taken place around 2800 BC, in the Indian Ocean, where an 18-mile diameter crater has been discovered at a depth of 12,500 feet.
However, a paper(x) published in October 2015 has suggested that a study of mass extinctions over the past 260 million year appear to have taken place every 26 million years coinciding with major asteroid/comet impacts.
So far 175 large impact craters(e) have been discovered all over our planet, many more are undiscovered having been destroyed over time by wind and water erosion or hidden by vegetation. In 2006, a crater with a diameter of 30km was discovered in the southern Egyptian desert. This discovery may solve a mystery in the same region that has baffled science for over seventy years, namely, the Libyan desert glass that covers an area 60 x 100 km. However, the largest known impact crater is the Vredefort crater n South Africa with a diameter of 300km (186 miles). But this may have to take second place to the 300 mile wide crater identified in Hudson Bay in North America. A 2015 report tells of two impact zones that total more than 400 kilometres across, which were identified in the Warburton Basin in Central Australia(t).
Although it appears that similar suggestions have been made since the 1950’s, the debate has now reached a new level. The Hudson Bay feature has generated even greater interest since Richard Firestone, a nuclear physicist together with Allen West and Simon Warwick-Smith published their claim that it was created around 11000 BC and had human witnesses who preserved their memory of it in their local folklore and that may have been responsible for the extermination of the Clovis people. Firestone’s tentative 11000 BC date for this event is earlier than Plato’s even more questionable 9600 BC date for the destruction of Atlantis might be connected since the event described by Firestone & Co. would have had global consequences and could have effected any suggested Atlantis location. In 2007, at a news conference during Joint Assembly of the American Geophysical Union, in Acapulco, Mexico, two archaeologists from the University of Oregon, Douglas J. Kennett and Jon M. Erlandson added geological evidence to support to Firestone’s thesis. In 2008 evidence of an exploding comet/asteroid over Canada during the same period was presented(c)by other academics from the University of Cincinnati. However, it must be noted that the Firestone hypothesis has encountered some criticism since the start of 2009 and must therefore be treated with due caution. This criticism appears to be gaining support according to a May 2011 report(h). In June 2012, James Kennett, son of Douglas Kennet mentioned above, was part of a team who announced further evidence of a major impact event 13,000 years ago extending from Pennsylvania and South Carolina as far as Syria(m).
Dr Reinoud de Jonge has written a number of articles(d) that drew on petroglyphs in Brittany to support his contention that the Earth had an encounter with a cometary body in 2345 BC. This would appear to complement the work of Mike Baillie and George Dodwell, who echoed William Whiston’s proposed date of 2346 BC, for an encounter with a comet that caused the biblical Deluge.
Since only 30% of our globe is exposed land, it is reasonable to conclude that 70% of impacts will have hit water, leaving little lasting evidence. However, at least ten of these identified impact craters occurred after the last Ice Age and at least seven of which date from around the third millennium BC, at period when there were widespread cultural collapses.
In a recent book the renowned dendrochronologist, Mike Baillie, has outlined compelling evidence from his own discipline combined with ancient mythologies to support the idea of extraterrestrial impacts in early historical times. May I suggest that the mythologies that possibly relate to multiple impacts are in fact recollections of a comet that had been visible for some time before breaking up under the gravitational influence of our planet prior to impact? This idea was developed by Baillie in a subsequent book written with Patrick McCafferty that focused on Celtic mythological figures. Comets rather than asteroids are more likely to have contributed to the development of myths since an asteroid would not have been visible long enough for it to develop an identity that would be remembered in legend. Graham Phillips has gone further and proposed that a close encounter with a comet in the middle of the 2nd millennium BC triggered the development of monotheism at that time. Furthermore, he contends that as the Earth passed through this comet’s tail, it introduced large quantities of an amino acid, vasopressin that heightened aggression in humans leading to large scale conflicts worldwide. This comet, 12P/Pons-Brooks is due for another close encounter with Earth in 2024.
A 2012 paper(o) by Fernando Coimbra investigates the influence of unusual astronomical events, in particular comets, on the subject matter of rock art. An earlier paper(p) by Coimbra looks at the swastika as a specific example of a reflection of such an event.
Mythologies, worldwide, offer evidence of these impacts and have been subsequently reinforced by classical writers who describe in non-scientific terms the effects of these extraterrestrial assaults. Pliny wrote in his Natural History (Book II, sec 91) of ‘A terrible comet was seen by the people of Ethiopia and Egypt, to which Typhon, the king of that period, gave his name; it had a fiery appearance and was twisted like a coil, and it was very grim to behold: it was not really a star so much as what might be called a ball of fire.’
Similarly the Greek myth of Phaëton has been interpreted as a record of an encounter with a comet. Edith and Alexander Tollmann also identified an 11,000 BC impact with the Köfels region of the Austrian Tyrol as one of the impact zones. The interpretation of ancient legends and myths is obviously a matter of subjective response, but the volume of such evidence is so great that the probability of a number of major impacts being within the memory of man, who relayed the experience down to us through the medium of tradition, is quite high.
The fact that our Earth is continually at risk of a cosmic collision, the physical evidence of recent and past collisions, the recording of impacts on the Moon and Jupiter compounded with stories in ancient mythologies offer strong grounds for accepting the possibility of Atlantis being destroyed as a result of a collision with an extraterrestrial object as a credible working hypothesis.
While an asteroid impact causing the destruction of Atlantis is relatively easy to accept, some authors have proposed even more dramatic scenarios where the impact was so great that it caused the Poles to change position and/or the Earth’s outer mantle to move relative to the inner core. There is little doubt that cosmic collisions of all the possible natural catastrophes pose the greatest possible threat to life on earth. There is an interesting website(c) that discusses both catastrophes and Atlantis. Another site(e) has a small collection of images of impact craters as seen from space. 2010 produced a frightening upward reassessment of the asteroid threat(f).
In 2001 NASA(k) identified 1,000 asteroids and comets orbiting close to Earth that are capable of causing catastrophic damage to our planet in the event of a collision. An interesting map was published(n) in February 2013 showing the locations of 34,513 impacts dating back to 2300 BC.
Recent deliberate encounters with comets and asteroids have produced images and data that have raised questions about the traditional description of comets being composed of ice and rock. The lines between asteroids and comets are becoming increasingly blurred and new definitions required(r). The trend now is to see asteroids and comets as part of a continuum. Evidence is emerging that the H20 previously associated with comets may have been OH radicals(s).
The 2014 landing on Comet 67P/Churyumov-Gerasimenko would appear to have destroyed the ‘dirty snowball’ description of comets, coined in 1950 by the noted astronomer, Fred Whipple, and should now be abandoned.
Although large asteroids or comets have caused and will again cause global catastrophes on a scale that we can only imagine, they are not the greatest potential threat to our existence. It is estimated that our galaxy, as in others, are also home to free-floating giant gas planets untethered to any star, which, if they wandered our way, could not only obliterate our planet but de-stabilise our solar system.(u)
Terry Westerman offers a fascinating overview of possible global impact sites on his fully illustrated website(y).
Fortunately, the death and destruction caused by comets is balanced by the probability that they are also the source of life on our planet. This idea is gaining greater acceptance with a further paper(aa) offering additional supportive evidence published in April 2016.
Nevertheless, improved vigilance is required if we are to believe Peter Brown of the University of Western Ontario, whose research in 2014 concluded(ab) that hazardous asteroids are 10 times more likely to hit Earth than previously thought!
(q) BBC Focus Magazine, July 2014, page 67.