(ORDO NEWS) — The fall of the Chelyabinsk meteorite was a loud signal for mankind about the danger emanating from space, writes Scientific American.
Over the past ten years, methods for detecting asteroids have become more advanced, and ways have appeared to change their trajectory.
An asteroid burst into the Earth‘s atmosphere, flying at a speed of almost 70 thousand kilometers per hour. This cosmic block, about the size of a tennis court, left behind a bright luminous trail in the sky – as if a second sun had appeared there, which rushed from the southeast to the northwest.
Entering the atmosphere at supersonic speed, the asteroid flared up, leaving behind a thick trail of evaporating rock. Due to the enormous pressure, this block began to change shape.
As a result, the pressure finally got the better of the asteroid about 40 kilometers above the Earth’s surface. It broke up into smaller pieces, each of which flew at a speed ten times greater than the speed of a bullet fired from a rifle.
These fragments also began to change shape, due to which a whole series of short but powerful flashes of light could be observed from Earth as they heated to the limit. In the end, the remaining pieces evaporated.
All this happened within a few seconds, and the last explosion happened when the asteroid was 30 kilometers above the Earth’s surface.
The energy of its residual movement instantly turned into heat. The resulting giant fireball briefly eclipsed the sun, radiating energy roughly equal to the explosion of half a million tons of TNT.
The powerful shock wave from this explosion reached the center of Chelyabinsk, located 40 kilometers to the north, in about a minute.
This industrial city of a million people was just beginning its day when a fireball swept across the sky. This stunning sight – and the long glowing trail of steam – made people go outside or look out of windows to see what was going on. And it was at that moment that the shock wave hit the ground.
The massive impact shattered windows throughout the city – the vast majority of those affected by the meteorite impact received glass cuts. Fortunately, no one was killed, and the damage to the infrastructure was relatively small.
If the asteroid had been larger, if it had been made of metal, or if it had crashed down at a sharper angle, this story could have turned out very differently, and the consequences would have been much more serious.
The fall of the Chelyabinsk meteorite became a wake-up call for the Earth. Very loud signal.
It also served as a valuable material for study – the largest event in the Earth’s atmosphere since the fall of the Tunguska meteorite in 1908. The smoking trail of the asteroid was observed by satellites, as well as by thousands of eyewitnesses and cameras.
The earth was strewn with small fragments of a meteorite, and one giant piece about one meter in diameter and weighing half a ton fell into the lake, from which it was then removed.
There are even footage from surveillance cameras, where you can see how this piece crashed into a frozen lake, leaving behind a very impressive splash of snow and water that shot up.
Pieces of the meteorite that scientists collected after the fall told them the difficult history of this asteroid. They were dotted with grooves and narrow slits.
Scientists have found that this 19-meter block was once part of a much more massive asteroid, which also suffered an impact, as a result of which a piece broke off from it, which crashed into the Earth and made a deep crack in it.
Isotope dating has shown that the first impact could have occurred as early as 4.4 billion years ago, when the solar system was less than 200 million years old.
Cracks in the Chelyabinsk block weakened it, which caused it to collapse high above the ground and managed to create a powerful shock wave.
It is not yet clear which asteroid is the “parent” of the Chelyabinsk meteorite. Scientists traced its trajectory back into space and found matches with asteroids 2007 BD7 and 2011 EO40. One of them may well be the “parent” of the Chelyabinsk meteorite, but so far there is no exact data.
Analysis of the fall of this block, along with smaller events, showed that similar “objects of collision” crash into the Earth much more often than previously thought. Chelyabinsk-sized asteroids crash into the atmosphere about every 25 years, but fortunately, most of them do so over the ocean or wilderness.
It is alarming that astronomers did not see this asteroid flying towards Earth until it crashed into the atmosphere. But asteroids are usually very dark celestial objects, and it is very difficult to notice small representatives of this class, even if they are close to Earth.
Just a few years earlier, the four-meter-wide asteroid 2008 TC3 became the first asteroid that people noticed before it crashed into the Earth’s atmosphere.
Since then, astronomers have been able to detect just six asteroids before they strike, including 2023 CX1, which lit up the Channel sky on February 13, 2023, as if to mark the decade of the Chelyabinsk meteorite fall. All of them were small and did not pose any danger to people.
Now that I’ve scared you enough with my stories about asteroid impacts, I have good news for you: people are rapidly improving their skills in detecting asteroids in space.
In the ten years that have passed since the fall of the Chelyabinsk meteorite, scientists have discovered about 20 thousand near-Earth asteroids – this is more than in the entire history of observations until 2013.
New survey telescopes such as Pan-STARRS and the Zwicky Transient Facility have come to our disposal, and better methods of data detection and analysis have been developed.
Very soon, the huge Vera Rubin Observatory and NASA‘s NEO Surveyor space mission will significantly expand the list of asteroids known to people that threaten the Earth.
But discovering them is only the first step. The next stage involves the adoption of certain measures. To this end, last September NASA launched the DART (Double Asteroid Redirection Test) mission, which hit the 170-meter asteroid Dimorph, a satellite of the larger asteroid Didymos, with a half-ton projectile.
The momentum from the collision changed the asteroid’s orbital period by more than half an hour. The results of that mission were even more impressive than scientists expected: a huge plume of rocks that separated from the surface of the asteroid gave it an additional impetus.
This proved that people could use such spacecraft to change the trajectory of asteroids.
More powerful explosions can significantly change the trajectory of a space block approaching the Earth. The explosion of a nuclear charge near a small asteroid will allow to evaporate a significant part of its surface.
The hot vapor will rapidly expand, acting like a rocket exhaust, and push the asteroid onto a new and, hopefully, safer trajectory.
Now there are some rather intractable problems with this method – for example, under the terms of the Outer Space Treaty, it is strictly forbidden to explode nuclear devices outside the Earth.
However, if a dangerous asteroid is flying in our direction at great speed, this may force people to make changes to existing laws and requirements.
After the fall of the Chelyabinsk meteorite, two spacecraft managed not only to approach small asteroids, but also to take samples from their surface (the Hayabusa-2 device has already delivered samples to Earth, and the OSIRIS-Rex device will do this a little later this year).
Both asteroids – “Ryugu” with a diameter of about a kilometer and “Bennu” with a diameter of about 500 meters – are piles of cobblestones, which are held together by their own rather weak force of gravity.
Probably all small asteroids are piles of boulders, and this property of them determines our confrontation tactics: their rather fragile structure will make it easier for us to strike at them. Imagine that you are trying to punch through a box of peanuts and you will see what I mean. But the DART mission also showed
The fall of the Chelyabinsk meteorite caught us by surprise, and although such small space objects can still slip past us without being noticed, we are confidently improving the technologies for detecting potential threats from space and developing a plan of action in case one of them decides to rush directly to Earth.
Large and dangerous asteroids are rare, but we just need to look at the Arizona meteorite crater to understand that we still need to take this threat seriously.
About 50,000 years ago, a 10 megaton explosion blew a hole in the desert over a kilometer in diameter, most likely destroying all the plants and animals that lived there at that time. This may have been one of the most recent direct meteorite impacts on Earth, but it certainly won’t be the last.
Of course, unless we take steps to prevent it.
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