65 million years ago, an asteroid 10-15 kilometers long, moving at a speed of 57 to 115 thousand km / h, crashed into the Earth. As a result of the collision, in a matter of minutes, a crater with a diameter of 180 kilometers was formed, the earth's surface melted, and huge mountain ranges rose. The explosion provoked a devastating megatsunami, and solid debris fell to the surface of the earth in the form of a rain of fire. Dust rose into the atmosphere, and the planet was covered with darkness for weeks, maybe months. The fall of the asteroid led to the Cretaceous extinction. 75% of all plant and animal species, including dinosaurs, died on Earth.
Astronomical and geological findings indicate that the repetition of such events is only a matter of time. Perhaps not tomorrow or in the next two hundred years, but it will definitely happen. In this regard, some astronomers fear that humanity is not making sufficient efforts to avoid the impending catastrophe. Asteroid Day, celebrated on June 30, is an international awareness campaign aimed at highlighting the challenges and threats looming over the planet. Last year, the UN declared Asteroid Day international. On this day, 700 events are held in 190 countries of the world, meetings are held with the participation of experts and scientists, which can be watched live. Discovery Channel will show a series of thematic documentaries, as well as the premiere of the film "How to survive an asteroid fall"in the production of which the activists of the information campaign took part.
Here is an excerpt from one of the popularizers of asteroid day, NASA astronaut and former Apollo participant Rusty Schweickart on the Discovery Channel: “Thousands of impacts hit the planet tonight. 100 tons of asteroids fall to Earth every day. Most of them are about the size of a grain or pebble, and only two or three bodies are about the size of a soccer ball. The most dangerous thing is that a larger body can fall on us, and then huge destruction will occur on Earth. And it's just a matter of time."
In addition to the threat of falling huge asteroids capable of destroying humanity, the initiators of the company warn of the real danger posed by more modest objects. The diameter of these bodies is tens and hundreds of meters, and they rotate in large quantities in the orbits closest to the Earth. As a result of a collision with one of these objects, entire cities or even regions can be destroyed.
Here's a recent example. A meteorite with a diameter of 17 meters, which fell in Chelyabinsk on February 15, 2013, provoked an explosion in power 35 times larger than the bomb dropped on Hiroshima. This fragment, discovered by scientists only after entering the Earth's atmosphere, turned into a real fiery projectile. Fortunately, this object was not very dense, so the car exploded in the air and did not cause serious damage to the ground. However, the explosion damaged 7,200 buildings in six cities and injured 1,500 people. Most of the injuries were received by people who were standing at the time of the explosion at the window to get a better look at what was happening.
At the beginning of the last century, a larger object caused even greater destruction. This is the Tunguska meteorite. On June 30, 1908, the object, with a diameter of 30 to 50 meters according to various sources, destroyed a total of 2 thousand square kilometers of Siberian taiga, or 80 million trees. This date is now celebrated as Asteroid Day. An explosion with a yield of 1000 bombs dropped on Hiroshima occurred over a desert area. But what would be the consequences if an asteroid fell in a densely populated area?
There is an opportunity to prepare
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Fortunately, space agencies are able to develop technologies to alter the trajectory of objects of this size, and astronomers have the tools they need to detect threats in time. However, scientists need broad public support and adequate funding.
"Unlike earthquakes, tsunamis or hurricanes, an asteroid collision is a preventable disaster," says astrophysicist Hakeem Oluseyi, one of Asteroid Day promoters. "With proper preparation, future collisions can be predicted."
Unfortunately, the problem of collisions with asteroids is not included in the priority tasks of any serious organization. In December 2016, members of the European Space Agency (ESA) did not approve funding for the Asteroid Impact Mission (AIM), which involved the creation of a program to test asteroid trajectory technology in collaboration with NASA. The preference was given to the ExoMars Mars exploration mission. Astronomers discover new space debris near Earth every day, but the detection rate is very slow.
If there is clear evidence of the destructive power of asteroids and technologies are being developed to prevent future collisions, why is this problem not taken seriously?
Debbie Lewis, an emergency and threat expert and popularizer of Asteroid Day, believes the main reason is that these events usually do not have eyewitnesses. “We all know what tornadoes, floods, hurricanes or earthquakes are because these events happen in everyone’s life.” Schweikart also agrees with her, who believes that "not every person in his life can witness the fall of a large asteroid." If there are no witnesses, then the phenomenon itself does not seem to exist.
See to believe
Large telescopes convince us otherwise. With the naked eye, traces of asteroid impacts over the past 4 billion years can be seen on the lunar surface. On Earth, such traces are hidden as a result of the movement of tectonic plates. In 2009, astronomers witnessed a powerful collision of the comet "Shoemakers - Levi 9" with the planet Jupiter. As a result of the collision, a spot larger than Earth was formed on the turbulent surface of the planet for several weeks. And what about the Earth? Between 1994 and 2013, 556 fireballs were detected in the earth's atmosphere, as well as flares and fireballs formed as a result of falling asteroids ranging in size from one to 20 meters.
But what happens outside of the Earth? It is believed that scientists have discovered only a hundredth of all asteroids in the solar system (fortunately, this is 90 percent of the largest asteroids). In addition, most are located at great distances - in the Kuiper belt or beyond, as well as in the asteroid belt, a large accumulation of debris between the orbits of Mars and giant Jupiter. These debris do not pose a serious threat to our planet.
But the situation may change if these asteroids or comets under the influence of solar gravity approach by less than 1.3 astronomical units (AU) to the Earth (AU is the distance from the Sun to our planet). Such objects are included in the Near-Earth Objects (NEO) category. Bodies reaching 150 meters in length and approaching the Earth at a distance of less than 7.5 million kilometers (for comparison, the minimum distance from Earth to Mars is 53 million kilometers) are considered Potentially Hazardous Objects (POA). On average, only 4% of NEOs are potentially hazardous.
Watching the sky
Just in case, astronomers are constantly on the lookout for luminous objects in the sky, which may be astroids or comets heading towards Earth. Thanks to this work, carried out by numerous observatories on earth and in space, including De Cam Neo Survey, NEOWISE and Catalina Sky Survey, 1,500 NEOs were discovered in 2015 alone. But that may not be enough.
“Thousands of astronomers make observations every night,” Schweikart says. "But we need more equipment to predict a dangerous collision, and for that we need to locate about 10 million objects." How much is left to find? At the moment, scientists have localized about 16,300 NEOs.
In this regard, the organizers of the Day of Asteroid drew up the "Declaration 100X", which states the need to achieve a hundredfold increase in the number of localized asteroids. Astrophysicist Hakeem Oluseyi believes that there are currently three ways to achieve this: with optical telescopes, radio telescopes and space infrared telescopes.
In turn, the White House in 2016 announced its goal to bring the percentage of open asteroids over 140 meters in size to 90%. According to the report on the national strategy for preparing for the HZS strikes, 28% of the bodies are currently open. "The power of the explosion when these objects collide with the Earth is equivalent to 60 megatons, which exceeds the volume of the energy released when testing the most powerful atomic bomb ever tested on Earth (Tsar Bomba with a capacity of 50 megatons)." Such a collision can lead to localized destruction.
300 thousand objects over 40 meters long
According to the Jet Propulsion Laboratory (JPL), in addition to objects several hundred meters in size, about 10 million bodies with a diameter of more than 20 meters, as well as about 300,000 bodies with a length of more than 40 meters, have not yet been detected. Such objects are capable of destroying entire cities.
The degree of danger (may collide with the surface, may cause damage, may lead to destruction) is an important characteristic in assessing asteroids. Usually, when a new OZS is opened, almost nothing is known about this object, and only after several months or even years of observations, scientists begin to determine its characteristics. Only in this way can you find out its size, shape, mass, chemical composition, exact orbit and possible collision angle. All these factors are very important for predicting the trajectory of the object and possible threats.
From Rusty Schweikart's explanations and expert Don Yeomans, it follows: "To protect the planet from collisions with asteroids, you need only three things: quickly detect them, quickly detect them and quickly detect them."
As Michael Küppers, a researcher at the European Space Agency (ESA) and a member of the AIM project, told ABC, "it takes 10-15 years to change the trajectory of an asteroid, although this depends on many factors." Therefore, it is very important to detect these objects in advance in order to be able to send missions in the future to change their trajectories. Coopers also acknowledged that there is a danger of objects entering from outside the solar system. An asteroid can pass near the Sun and go unnoticed. It may take such an object only a few months to reach Earth, and it will be very difficult to avoid colliding with it.
Spaceships and atomic bombs to change the trajectory of asteroids
Now there are several theoretical technologies for changing the trajectory of asteroids. A gravitational attractor is a method in which a large spacecraft uses its engines and its own gravity to gradually change the course of an asteroid. Kinetic ram is a controlled collision at high speed of spacecraft with an asteroid, which leads to a displacement of the debris trajectory. Laser ablation - the use of pulses of light to affect the surface of an asteroid, resulting in the formation of jets of steam and particles that can change the orbit of the body. The possibility of using a nuclear charge is being considered as a last resort. This is the only way to destroy or deflect a large object, but as a result, many small fragments can form,and it will also not be possible to slow down large fragments.
Each year, one car-sized asteroid burns in the atmosphere, turning into a ball of fire. Once every 100-1000 years, an object the size of a football field falls to Earth, capable of destroying an entire city. With a frequency of several thousand years, an asteroid arrives capable of destroying the territory of an average state. It was such an asteroid that fell in Southeast Asia 700 thousand years ago. About once every 10 million years, a collision occurs with an object several kilometers long. If such an asteroid fell right now, it could destroy all of humanity or lead to millions of victims.
Such phenomena occur very rarely, therefore, at the moment, not a single death has been recorded in connection with the fall of a meteorite. Compared to this space debris, environmental pollution, harmful radiation or car traffic are more tangible threats. However, this is a real threat, the popularizers of Asteroid Day warn us.
“I think it's imperative that people understand how much this matters to each of us, not just politicians, scientists, engineers or the people involved in this project,” says filmmaker Greg Richter, one of the Asteroid Day Campaigners. "We have to do this for our planet and for our species." For this, in his opinion, it is necessary to draw wide public attention to this issue. The economic costs of this project will not exceed the amounts allocated for other research projects.
“It's like car insurance for me. Many people drive and admit that sooner or later they will get into an accident,”Schweikart concluded. “We don't want to worry about it, we want to pay for the insurance. (…) Now we need insurance to be able to find and change the trajectories of these objects. In the future, when that moment comes, we will be able to save human lives. That's all. We can involve the entire planet in this activity if people pay attention to this topic. I hope that thanks to Asteroid Day, people will be able to get enough information and help their political leaders make the right decisions.”
As with other global challenges, such as climate change or poverty, solving a large asteroid impact is perhaps another chance to prove that humankind can join forces for the welfare of future generations. Alternatively, you can cross your fingers and pray that this disaster will not happen as long as our civilization exists.
Gonzalo López Sánchez