International Asteroid Day:
The United Nations General Assembly declared June 30 as International Asteroid Day, in December 2016, in order to "observe each year at the international level the anniversary of the Tunguska impact over Siberia, Russian Federation, on 30 June 1908, and to raise public awareness about the asteroid impact hazard."
It is meant to "raise public awareness about the asteroid impact hazard" and "crisis communication actions to be taken at the global level in case of a credible near-Earth object threat".
Tunguska impact over Siberia: A continental danger evaded
On June 30, 1908, near the Stony Tunguska River, an unknown celestial object exploded in a sparsely populated region, the Central Siberian Plateau. It produced the energy force equal to 1000 times the force of the atom bomb that was dropped on Hiroshima.
It destroyed a massive stretch of a conifer forest of 2000 square kilometres, roughly the size of Britain. Around 80 million trees were flattened and burned.
If the whole of Greater London was a forest, the whole of it was destroyed by the blast and the resulting fire. A bolide brighter than the Sun would have been seen approaching from halfway across France.
In fact, so loud was the sound even 800 kilometres from blast epicentre. The gunfire-like bangs of the impact would have been heard across Britain and Ireland, over Europe as far as Switzerland.
A massive amount of dust was thrown up in the sky. The rising dust hovered over the European nations as well as Central Asia, reflecting enough light that caused bright luminescence.
Tungus clans wiped out
Although few claim that no lives were lost, descendants of eyewitnesses say that hundreds of people died because of the blast and the worst hit were the Tungus people.
Whole clans were simply wiped out of existence because of the explosion.
The sole eyewitness of the event reported seeing a blinding light high in the sky right above the forest.
A 111-year mystery - the Tunguska Event
The Eastern Siberian Taiga incident was classified as an impact event even though no impact crater has been found.
The unknown object is assumed to have disintegrated at an altitude of five to ten kilometres rather than hit the surface of the Earth.
The impact energy of the event remains uncertain.
After the impact of the event had settled, a debate on it began as to if it was a meteorite or an asteroid after all. It popped up since the event lasted an hour. This is completely against meteorite theory. Also, an object from outer space came in and exploded in the air, with not even minuscule amounts of material left behind.
Expeditions to unearth the unsolved
Leonid Alekseyevich Kulik, a Russian mineralogist, led the first Soviet research expedition to investigate the Tunguska event, in 1927.
Accompanied by the local Evenki hunters, Kulik found upright trees which were scorched and devoid of branches. Looking closer, he found holes that he mistakenly concluded to be meteor holes. Back then, he did not have the necessities to excavate the holes.
During further expeditions in the 1950s and 1960s, microscopic silicate and magnetite spheres in siftings of the soil were found. They were later discovered in tree resin as well.
They showed that high proportions of nickel relative to iron were also found in meteorites, leading to the conclusion they were of extraterrestrial origin.
"John's Stone" was found by John Anfinogenov - a specialist in aerial photography from Tomsk - in 1972 buried in permafrost close to the epicentre of the 1908 Tunguska blast.
Even in 2013, fragments of rock retrieved from a remote corner of Siberia to help settle the enduring mystery.
In 1930, the British meteorologist F J W Whipple suggested that the Tunguska body was a small comet, and this view has generally been supported by Russian astronomers.
D W Hughes, in his publication 'Nature' (1976), said that the object was probably a small comet.
An American astronomer Fred Whipple (1975) thought it more likely that the bolide was an inactive, low-density, friable body.
Ľubor Kresák, a Slovak astronomer in 1978 stated that the body was a fragment of a short-period comet 2P/Encke.
In 2007, a group in Bologna debated with the evidence of a Lake Cheko, in the Tunguska region as a possible impact crater from the event.
Astrophysicist Wolfgang Kundt proposed that the Tunguska event was caused by the release and subsequent explosion of 10 million tons of natural gas from Earth’s crust.
Multiple theories such an accident during one of the experiments of Nikola Tesla, a Serbian-American inventor or even the Thunder God – Agda descending have cropped up.
But the mystery of this "asteroid strike" still remains unsolved.
More than 45 literary features, 30 plus movie, cartoon and comic references, even in games and songs, Tunguska is embedded in pop culture.
Ghostbusters (1984), Indiana Jones and the Kingdom of the Crystal Skull (2008), Star Trek: The Original Series episode "That Which Survives", a two-episode story arc of The X-Files, Doctor Who episode "In the Forest of the Night", even a New Yorker short story 'Chicxulub' has featured this phenomenal event.
From notable science fiction writers like Isaac Asimov and Arthur C Clarke to Sherlock Holmes pastiche "The Adventure of the Russian Grave" by William Barton and Michael Capobianco, the event is creatively unravelled.
Even Marvel and DC comics and games such as Call of Duty and Assassin's Creed have mentioned it.
On June 22, a car-sized asteroid was discovered by scientists in Hawaii hours before it slammed into Earth and burned up in the atmosphere this past weekend, news sources report. The asteroid's impact was so powerful that even satellites in orbit spotted it.
According to the report: "This is only the fourth time in history that an impacting object is observed prior to atmospheric entry."
Lorien Wheeler - a researcher from Ames working on NASA's Asteroid Threat Assessment Project - told Phy.org: "Because there are so few observed cases, a lot of uncertainty remains about how large asteroids break up in the atmosphere and how much damage they could cause on the ground."
"However, recent advancements in computational models, along with analyses of the Chelyabinsk and other meteor events, are helping to improve our understanding of these factors so that we can better evaluate potential asteroid threats in the future."
The Tunguska impact, even after a century, is still a story of caution for people to know the disaster levels asteroids can become if they are left unrecognised. Having proper knowledge of the most vulnerable areas of impact is necessary, not just to save humanity, but the planet itself.