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If you clean the gutters of your roof, take note that the dirt you throw may come from the space.
The new book "Cosmic Impact: Understanding the Threat of Asteroids and Comets for the Earth", by Andrew May (Icon Books), gives an overview of the potential dangers that we may face one day from near-Earth objects (NEO). On a smaller scale, objects falling from space on Earth are a daily reality.
"On average, about 100 tons of meteor dust fall on the planet," May writes. "One of the best places to find it is on non-porous surfaces such as city roofs and gutters. . . The mud in your gutter almost certainly contains some particles from the space. "
Dust particles from space do not put the planet and its inhabitants in danger of death. Asteroids like the one that made dinosaurs extinct are the most disturbing.
The Chicxulub Crater, of a length of 124 kilometers, located near the Yucatan Peninsula in Mexico, was forged 66 million years ago when an object located at a distance of 39 miles. about 69 kilometers struck the area from space. The resultant fire and dust – the latter covering the earth's atmosphere and virtually blocking the sun – eventually killed the dinosaurs.
If we find ourselves today with a similar object, the result would be similar.
"The devastation would be so much bigger than anything in the human experience, it's hard to imagine," writes May. "If the impact occurred in the sea, the water would boil. If it was on dry land, large areas would be ravaged by fire storms. The dust raised by an impact of Chicxulub's size would prevent sunlight from reaching the Earth's surface for months or even years to come. "
The good news, however, is that the probabilities that such an object hits the Earth in our lifetime are close to zero.
The Torino scale considers the size of the NEOs and the chances they will touch the Earth over the next hundred years to place the possible danger on a scale of 1 to 10.
At present, the coming century does not seem dangerous.
"There is currently no known object with a Torino rating as high as 1," writes May. "All we know is either too small to cause damage, or there is no chance that the vehicle will collide with Earth in the next hundred years."
However, this has not always been the case. Just as late as 2004, an object bearing Torino's ominous figure, consisting of 4, was spotted, indicating a decent chance of contact that could cause untold destruction.
When scientists spotted an asteroid 350 meters that year, they calculated more than 1% chance of colliding with the Earth in 2029. Given its size, this would have resulted in an explosion in the "Thousand-megaton class". By way of comparison, May writes that the nuclear bombs exploded above Hiroshima and Nagasaki were about 0.02 megatonnes each.)
Fortunately, later calculations "have refined the orbit and excluded a collision," writes May.
But while the risk of an asteroid breaking the planet is currently zero, outer space swirls with smaller objects that, without threatening humanity, can still cause real damage.
In fact, they already have.
On June 30, 1908, the "greatest cosmic impact of the history of history" was perceived when a "small rock asteroid, even a tiny comet," subsequently exploded between 30 and 70 meters, on the "valley of the sparsely populated Tunguska River in Siberia. "
The location was lucky because the explosion, a thousand times more powerful than the bombs used in Hiroshima and Nagasaki, did not kill anyone.
"When the object Tunguska entered the atmosphere of the Earth, [there] was an explosion of the order of 10 to 15 megatonnes – typical of a cold war nuclear weapon, "May writes. "Its most obvious effect has been to burn and flatten trees – 80 million of them – within a radius of 30 km around the" zero point "of Tunguska."
May quotes a scientist named Gerrit Verschuur, who wrote the following: "Estimate the number of victims of a Tunguska-like event in a populated area. . . suggest no less than 5 million deaths. "
That said, the possible effects of a smaller NEO that does not destroy the planet are not all negative, because comets can provide vital resources to our planet, and may have already done so.
May again quotes Verschuur, who wrote in 1996: "A dozen massive comets contain enough water and organic molecules to provide all the water and biomass of the Earth." This can also apply to some asteroids and meteorites.
May writes, indeed, that a "significant fraction" of the water and organic organisms of the Earth has arrived here exactly in this way.
He noted that a meteorite arriving in Australia in 1969 was found to contain "at least 15 different types of amino acids, as well as a significant amount of water – about 10% by weight".
"Impacts. . . were much more numerous in the beginnings of the Earth's history, "he writes. "It is therefore not unreasonable to imagine that they have brought much of the raw material necessary for the formation and development of life."
Since a NEO collision with the Earth would probably destroy life more than create it, the United States monitors the atmosphere as it prepares for possible intervention.
NASA constantly observes the sky with the help of large telescopes from Arizona and Hawaii. But even this defense carries risks.
In February 2013, astronomers identified an asteroid that they named 367943 Duende, which would pass close to the Earth without making contact.
Some skeptics have thought that the asteroid would hit us despite the assurance of scientists, which is not unusual. When "a huge meteor exploded in the heavens above Chelyabinsk [Russia] that day, "skeptics feel justified.
But scientists were not mistaken about Duende. It turned out that the meteor that had exploded was an entirely different phenomenon that they did not notice because it "was coming from the direction of the sun", which meant "qu & rt; It was only above the horizon in the light of day, when the telescopes could not see it. "
"This blind spot around the sun is a constant irritation for NEO fighters," writes May. "They just have to hope that all that is hiding out there before it hits us."
Although there is no way to defend against an object that we never see coming, if an NEO was to be spotted on a direct path to the Earth, there are options for the defense of the Earth. Again, they are all risky.
An asteroid can be destroyed by detonating a nuclear weapon on it, but the many resulting fragments would continue along the same orbit, making flashback as damaging as the miss.
For this reason, scientists would be much more likely to try to divert the object to throw it completely out of its orbit.
The NEO would need to be directly pushed out of its orbit or change its speed. Neither direction nor speed would be important. Anything that significantly changes the course of the object would prevent it from making contact.
The key word, however, is "significantly".
"A NEO big enough to worry us will be a lot more massive than anything we usually push," May writes.
"A rock of one kilometer represents more than a billion tons, or about 10,000 aircraft carriers. How are we going to push this into a new orbit, even if it is only a short time? "
An answer takes us back to the nuclear option.
The pioneer of the hydrogen bomb, Edward Teller, proposed, in this scenario, to place a nuclear explosive on the object itself, as the force of the detonation would propel it out of its orbit. Unfortunately, this would require "a spacecraft to match the gears with the asteroid and land on it."
It would take years and leave the project open to all kinds of complications.
Others have suggested that detonating the device near the object rather than on it could have the same effect. But given the risk – and that sending a nuclear device into space would break several international treaties -, the use of this method is unlikely.
But throwing the object out of its orbit would not need a nuclear device if we could design a spacecraft or other thruster to strike it directly.
When NASA sent a probe on a comet that passed in 2005, it was to inspect it, not to distract it. That's what speed has achieved, by changing the comet's orbit by 0.00005 millimeters per second and giving the tactics credibility if needed.
Fortunately for us, as we have already mentioned, it is most likely theoretical, since the probability that an NEO is large enough to cause significant damage to the Earth during our lifetime is practically nil.
Unless, of course, we lose it in the sun.
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