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The year is 1808. In the inner part of the Solar system, in a very eccentric orbit, a dark, fragmented, stony, 40 meter large body of irregular shape, covered by a multitude of craters, a member of the NEO group heads for it’s meeting with Earth.
June, 1908., just below the Arctic circle in the area between the Podkamenaya Tunguska and Nizyaya Tunguska rivers, flora and fauna are just awakening after a long, cold Siberian winter. The area is covered with thick woods, swamps, peat bog, termocarst circular structures of glacial origin. In the forest the trees fight for that little nutrients which can be found in 30 centimeters of defrosted soil.
Picture 1: Irregularly shaped, fragmented NEO object on it’s collision trajectory with Earth, a couple of minutes before entering the atmosphere. Because of the tidal forces, the body’s disintegration has already begun.
Picture 2: Through the beautiful green of short summer, bordered by the width of it’s sandy shores, curles the cold Tunguska river towards the rivers Jenisey.
Podkamenaya Tunguska river, together with Nizyaya Tunguska encircle the area known as “Tunguska-land at the end of the world”.
Picture 3: Kimchu river, at the border of the devastated area. Hundred years old trees grow by it’s banks, while the river flows it’s curly path through the Siberian forest.
Approaching our planet, the Earth’s gravitation overcame the gravitational interactions of the asteroid’s fragments. All of those, up till then, gravitationally linked particles started dissipating and creating an elongated cloud of material with the biggest piece in the middle. On the 30th of June, 0:14 UT, while colliding with the upper portions of the atmosphere every single particle entered it as a separate, independent, body. Smallest particles became destroyed through ablation, while the bigger pieces, though loosing a large part of their mass in the ablation process, succeed in reducing their velocity and fall as dark bodies along ballistic paths towards the Earth surface - towards an inhabited part of forest, some 70 km northeast of Vanavara.
Main body, weighing a couple of million tons, lost almost no speed at all. In it’s trajectory, it overcame all the other pieces. The process of ablation vaporized hundreds of tons of its mass, leaving a black trail across the sky, witnessed by observers. The glow was of such intensity that it was impossible to directly observe the fireball itself. As it approached the Earth surface, the aerodynamic pressure at the front side of the body grew and at the height of about 10 km, when the pressure became greater than the cohesive forces holding the body together, it shattered into small pieces.
In mere hundreds of a second, at the place of the solid body which entered, stood billions of smaller pieces which were stopped in the thick part of the atmosphere, turning all of their kinetical energy into heat : near 15 megatons. The Tunguska body existed no more. At the height of 8 km only plasma existed. Sphere of plasma half a kilometer wide and heated to 15,000 C. Down on the surface, in a radius of around 30 km around, tajga forest burst into flames because of the enormous amount of IR radiation radiated by the hot, rapidly ascending and expanding plasma cloud above. Large portion of the body’s mass was ejected back into the stratosphere along the same path the body took when penetrating the lower layers of atmosphere. Around the plasma toroid, atmospheric oxygen and nitrogen started to burn forming large amounts of nitrogen-oxides. A couple of smaller clouds survived long enough to protect a couple of pieces of the forest from the total holocaust the fireball was creating. In the mean time, shock waves created by the body’s penetration combined together with shock waves from the explosion itself traveled towards the surface. The trees directly under the rising plume were stripped of their burning branches, being left there as the pointers to the nemesis directly above. The cloud of fire above continued to ascend and widening. Underneath, in the area of reduced pressure caused by the rising plume, a giant mass of air was being pulled upward, creating (due to the fall of the pressure), a white bell-shaped form of condensed drops.
Under the bell, caused by vertical flow, a pile of burning wood, leaves and ashes started to rise. Discharges inside the toroid and in the direction of the surface gave a finishing touch to the scene of complete mass death and destruction of the area. A couple of miles away from the epicenter, shock wave hit the trees under an angle, shutting them down and shattering them into hundreds of bits and pieces. At larger distances, as the shock wave lost strength, it pulled the trees out of the earth, together with their roots, laying them circularly around the epicenter. Behind the shock wave, all that was left was 2150km2 of burning and leveled tajga. High into the stratosphere, large amounts of ashes, dust and nitrogen oxides were ejected. Days after the disaster, night sky of the northern hemisphere glowed. The dust ejected from the explosion site reflected the sunlight towards the night part of the Earth, helped by favorable position of the Sun near the summer solstice. The ozone hole created by the explosion grew wider and could be measured months later in California. Forest fire lasted for four days, and burning of the humid and resin rich leaves of larch raised great amounts of toxins into the atmosphere, joining the nitrogen oxides already there. The survivors had more sunlight and nutrients, resulting in faster growth of vegetation. After that, in the harsh conditions of subarctic climate, the nature needed a long time to recover from the catastrophe, and it’s traces can be witnessed today, 90 years later.
Picture 4: Plume of explosion debres ejected towards the stratosphere.
For those wanting to find out more about the event, we recommend the following literature.
