NASA draws the robot portrait of the asteroid of the Tunguska event

NASA scientists studied in detail the Chelyabinsk event, which took place in February 2013, to better understand the Tunguska explosion in 1908 and to determine the main features of the object at the origin of this event. event. They have also reevaluated several millennia, not centuries, the average interval between impacts of asteroids of this type with the Earth.

111 years ago, on June 30, 1908, at 12:14 UTC, was held in Central Siberia, in  the Tunguska region , one of the most  powerful recorded explosions in history. According to some sources, it would have been 1,000 times larger than that caused by the Hiroshima bomb 37 years later. The earth quaked to the Irkutsk Magnetic Observatory ( magnitude 5), more than 1,000 km from the site of the blast around which 60 million trees lay on an area of ​​2,000 km 2 . Only one death has been recorded as the region concerned is isolated.

The Toungouska event has it interesting that it is the greatest impact ever observed by modern humans. It is characteristic of the type of impact against ”  which we will probably have to protect ourselves in the future  “, says David Morrison, research scientist in planetary sciences at the Ames Center of NASA .

Since then, several studies have been started to find out what happened. The first took place with a scientific expedition sent on site in 1927, 19 years after the event. At that time, no trace of meteorite had been detected and many scientists had then favored the hypothesis of the impact of a comet , after discarding other assumptions such as volcanic events or mining. Since then, scientists have become almost certain that the bolide that struck the Earth was a meteorite and not a comet.

As cases of observations are fortunately rare, our understanding of the processes that determine how asteroids break up and explode when they enter the atmosphere is limited. Nevertheless, recent advances in modeling and analysis of events such as Chelyabinsk and other meteorological phenomena help to improve this knowledge in order to better assess the potential threats of asteroids in the future.

The Chelyabinsk event took place six years ago on February 15, 2013, east of the Urals, Russia. That day, a 19-meter asteroid exploded in the sky causing a shock wave that caused up to 1,500 wounded and extensive material damage. This ball of fire helpful enabled researchers to apply modern techniques of computer modeling to explain what was seen, heard and felt. It was thus possible to accurately determine the size of the car, its trajectory and its speedentry into the Earth’s atmosphere. The resulting interpretation is that Chelyabinsk was most likely a stony asteroid about the size of a five-storey building that broke down about fifteen kilometers from the ground. This generated a shock wave equivalent to an explosion of 550 kilotons. Unlike the explosion of the Tunguska, this explosion was not enough to tear down trees or knock down hard structures. According to the current knowledge of the asteroid population, an object such as the Chelyabinsk meteor can hit the Earth every 10 to 100 years on average.

Based on this method of work and the analysis technique used for the Chelyabinsk event, a study conducted by NASA’s Ames Center and sponsored by the Planetary Defense Coordination Office concluded that the explosion of Tunguska region originated from a massive object colliding with the Earth. The object was a telluric body and not iced, measuring between 50 and 80 meters in diameter. It entered the Earth’s atmosphere at around 55,000 km / h and disintegrated, releasing the equivalent of between 10 and 30 megatons of energy . Recall that the power of the Hiroshima explosion was estimated at 15 kilotons.

The risk of a similar impact postponed indefinitely
New research conducted by NASA indicates that asteroid collisions of this jig with the Earth are less frequent than previously thought. These studies were combined with the most recent estimates of the asteroid population and the researchers concluded that the mean interval between such impacts was in the order of millennia, not centuries, as previously assumed, based on previous estimates and smaller sizes.

That said, if the risk of a potentially devastating impact fades away, we must remain aware of this danger and prepare for it. Asteroids hit Earth and others will hit again.


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