Nikolai Zheleznov: if the fall of an asteroid is inevitable, then it is better to go to the ocean

Every month, potentially dangerous asteroids fly past the Earth, but do not cause any physical damage, but only cause information noise. Nikolai Zheleznov, a senior researcher at the Institute of Applied Astronomy (IPA) of the Russian Academy of Sciences, told in an interview about why they should not be afraid despite such a formidable name, how earthlings could defend themselves from such objects, and also in what case humanity will be able not to repeat the fate of dinosaurs. correspondent Denis Kayyran.
— Nikolai Borisovich, the media often scare readers with announcements of dangerous asteroid flybys close to the Earth. How seriously should such messages be taken?
“We shouldn’t take it very seriously, because if there really was some real threat, there would be much more noise. Let me explain how it happens. When a new object is discovered, in order to determine its orbit, you need at least three positions, three points in the sky. From them, we get coordinates that uniquely display the orbit. But nothing is perfect in nature. Due to optical defects and the trembling of the earth's atmosphere, instead of points, we see these positions in the form of spots, that is, with some error. When we start building an orbit into the future or into the past, we get not the point where the object will be, but some area, which is called the probability ellipsoid or the error ellipsoid. Often, when calculating the orbit for the future, it turns out that the Earth falls into this area. And now they begin to trumpet about it — with a probability of one hundred-thousandth in 100 years, the Earth can collide with this asteroid. Then, with an increase in the number of observations, the orbit is determined more precisely. The error will never go to zero, but will decrease, and it turns out that the Earth is leaving this zone.

– Are there any asteroids that have not ceased to be potentially dangerous after updating the data?

— It happens that at first the probability increases, but then it still goes to zero. For example, one of the most dangerous objects, the asteroid Apophis, was discovered in December 2004, and according to the first series of observations, the probability of a collision on April 13, 2029 increased and increased to almost 3%. Not one millionth or one thousandth, but 3%. Then it turned out that in 2029 it will still fly past the Earth, but very close — at a distance of 32 thousand kilometers, approximately like geostationary satellites fly. It is quite large — 300 meters, and will be visible as a star of the third magnitude, bright enough. It will fly so close that even an error in determining the orbit of a kilometer or two before the flyby can lead to an error of thousands or even millions of kilometers after the flyby. Therefore, it must be observed now, because there is a possibility, a weak one, of course, that it enters into resonance with the movement of the Earth and will return every seven years. It was previously thought that in 2036 it could collide with the Earth. But the latest data shows that it will fly much further, somewhere in a million kilometers.
— What will be the consequences if it does crash into the Earth?
— Very serious, but it will not lead to a global catastrophe. In order for a global catastrophe to happen, you need a body from one and a half kilometers in diameter. But 300-meter bodies are guaranteed to reach the surface of the Earth. The main threat is kinetic energy, which, upon collision, instantly turns into thermal energy and leads to an explosion. The Chelyabinsk body, which was 27-30 meters, exploded in the atmosphere before reaching it. The power of the explosion was somewhere around 200 kilotons. And here the asteroid is 10 times larger, which means it is a thousand times heavier, so the explosion will be measured in tens of megatons — enough to erase any state or region.
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– What if it hits the ocean?

– A giant tsunami will rise, which will wrap around the Earth several times. Waves will reach several hundred meters, maybe up to a kilometer. They will simply wash away the entire coastline.
— How are asteroids classified? Are there many of them as dangerous as Apophis?
– There is a concept of near-Earth asteroids (NEA). These are those whose perihelion distance, that is, the point of the orbit closest to the Sun, is less than 1.3 astronomical units (the distance from the Earth to the Sun). There are now about 32 thousand found. The orbits of the most dangerous objects such as Atira lie entirely inside the orbit of the Earth. There are 32 of them open. They move from the direction of the Sun, so they are very difficult to detect. Either only at sunset or at dawn. In addition, there is also such a class of objects as potentially dangerous objects. These include those that at least once either approached, or will approach the Earth's orbit at a distance of less than 7.5 million kilometers. About 10 thousand such asteroids have already been discovered.
Another class stands out — objects larger than one kilometer. This is an important psychological value, because a collision with a body more than one and a half kilometers leads to a global catastrophe.

To date, almost all kilometer-long bodies have been discovered. The speed of opening is not something that has dropped to zero, but even became negative. The fact is that we see the asteroid as a point object and only by its brightness can we estimate its size. And brilliance is proportional to the product of albedo (reflectivity) and the visible area of ​​​​the object. When the albedo turns out to be brighter than expected as the refinement progresses, the size of the asteroid «reduces». About 880 such kilometer-long bodies are now known. Potentially dangerous asteroids larger than a kilometer have been discovered to date 156. They all do not pose a threat to the Earth, they simply pass by the Earth. But this does not mean that we can live in peace. Firstly, there is still a discovery of asteroids larger than 140 meters. Why this particular number? Because they are guaranteed to reach the Earth, leave a crater. Now the task is to find these bodies, many of them have not been found yet.

– What percentage has not yet been discovered?
“That I cannot say. But I think that at best we have discovered half.

— Should we try to speed up their discovery, and how can this be done technically?
— The rate of detection of dangerous objects increased dramatically at the beginning of the 2000s, because programs for automatic monitoring of the sky appeared, telescopes were allocated for precisely one purpose: the search for dangerous objects. The program is set, which parts of the sky to scan. The telescope itself scans them, processes them, that is, the objects seen are identified, if some new one, then an orbit is built for two nights and it replenishes the preliminary catalog of asteroids. There are two active programs — Catalina Sky Survey and Pan-STARRS. Both are American. And a small percentage of discoveries are accounted for by all other programs. We do not have such a national program.
— How developed is the system of protection against such threats, and is it needed at all, given how low the probability of an asteroid hitting the Earth is?
— Although the most dangerous of the existing asteroids have been selected and discovered, the NEA group is replenished. New bodies arrive from the main asteroid belt between the orbits of Mars and Jupiter. At any moment, you can expect new guests who can go straight to Earth, so you need to watch. Modern technologies make it possible to develop an asteroid collision avoidance system. The most effective means is a deviation from a dangerous trajectory. Already even experiments were carried out such — they hit with a blank and watched how the orbit changes. If you push an asteroid just a tiny bit, it goes past the Earth. But to implement this method, the political will of the countries of the whole world is needed, because this is a very expensive and science-intensive procedure.

As for the national level. We have a bad astroclimate, a very rainy country. Therefore, either we need to build stations somewhere in other states, or create a constellation of telescopes in orbit so that we can cover most of the sectors of the sky.
If a dangerous object is detected, instantly in automatic mode, you can calculate its trajectory, determine the area where it can fall. If this happens on the territory of Russia, then the Ministry of Emergency Situations is automatically notified and it is possible to organize the evacuation of the population in time.
— When can we expect the next Chelyabinsk meteorite? How often do bodies arrive on Earth that were not known before?
— The Chelyabinsk body was not a meteorite. In space, in airless space, asteroids and meteoroids move, and experts are still arguing where their border is. I am a supporter of the border being 30 meters. In general, a meteoroid is just a small asteroid. When this body flies up to the earth's atmosphere and enters it at great speed, there is friction against air molecules, the temperature rises, the body begins to melt, glow, leaves a trace in the atmosphere, this phenomenon is called a fireball. What was seen over Chelyabinsk in 2013 was a fireball. But when something falls on the Earth, and then we go around collecting solid matter, these pebbles, then it is already called a meteorite. The Chelyabinsk fireball, of course, was impossible to detect, because it was coming from the side of the Sun. Such events occur two or three, maybe four times in a century. But that doesn't mean we have another 30 years left, it could be tomorrow, it could be 150 years from now.

– If a large object that threatens the Earth suddenly appears, will humanity have the opportunity to react?
— It's called the third stage — a terrible scenario when an asteroid is discovered at the stage of its entry into the atmosphere. It is unlikely that it will come to this, because after all, the observation of the sky is underway. But if he nevertheless suddenly “jumped out” and flies, then now, at this stage, we cannot do anything. We will not have time to reject such an object, and we will have to launch a missile with a nuclear warhead and destroy it. It's better to fall a swarm of small debris than one large body. Half of the small debris can burn up in the atmosphere, and the other half can slap craters, but the Earth's atmosphere will remain. Technology makes it possible to launch a rocket even in half an hour, if it were ready. But for this they need to be kept ready and trained to shoot at asteroids.
— What is the likelihood that humanity will suffer the same fate as dinosaurs?
— Sixty-five million years ago, the Earth collided into a 10-kilometer body. During such collisions, a huge amount of earthly matter will be thrown into the atmosphere — sulfur, dust, all this will rise into the stratosphere, the winds will disperse it throughout the Earth, and it will be covered with a dust blanket through which the sun's rays will not be able to penetrate. The Earth will receive much less solar energy and the temperature on the surface will drop, so-called nuclear winter will reign for several decades. This is how the dinosaurs died, because they could not adapt to climate change, but small animals could by hiding in holes.

There are no such large asteroids among NEAs. The mechanism of replenishment of a group of asteroids is designed in such a way that only bodies up to several kilometers can be pushed out of the main asteroid belt. Therefore, there will definitely not be such a collision that the Earth will split. Bodies about 10 kilometers in size arrive once every 100 million years on average. This does not mean that we have 35 million years ahead of us. It could happen in 10 years, or maybe in another 100 million.
So I think we'd rather destroy ourselves. But such a possibility exists. In addition to asteroids, there are also comets, they have an even more terrible effect, because they can go towards the Earth with a relative speed of not 10-15 kilometers per second, but 70.
The probability is negligible, literally millionths of a percent, but it is still non-zero. We see comets all the time. There are short-period comets, like Halley's comet, 232 of them are known. And there are long-period ones, they come from the Oort cloud, this is a cometary region somewhere on the periphery between the Sun and other stars. They have a period of tens of thousands of years.
— Does humanity have a chance to survive in a global catastrophe, as small mammals could survive before?

— If a collision is inevitable, then it is better, of course, if this body still falls into the ocean. Let a gigantic tsunami several kilometers high rise, let it wash away everything completely, wash the whole Earth, except, perhaps, the highest mountains. The main thing is that the atmosphere survives. Then, if at least some of the people survive in the caves, they will, in principle, be able to partially restore the landscape, with seeds, maybe they will save some of the animals, but still, to some extent, the biota will be preserved so that the population group that remains will be enough to live. But if the asteroid collides with land, and dust rises, then the atmosphere will be spoiled. It is not clear how to survive. It will be necessary to sit in caves for decades, until the generation of people changes, there will be practically no living creatures left on Earth, how can all this be restored later? Civilization will almost certainly be doomed.

– Have signs of extraterrestrial life ever been found in meteorites that have fallen to Earth?
— All these bodies are examined under a microscope, it seems that even somewhere some fossils of microorganisms were found. However, this can all be disputed. Moreover, on many fragments of meteorites, the «building blocks» of biological life — amino acids — were found. At the very least, complex molecular compounds are likely to exist. That is, even if not life itself, then the «bricks» of this life can be brought. One of the hypotheses of the origin of life on Earth just implies that water was brought to Earth by comets. And comets are, in fact, a big «snowball», they contain a lot of similar bricks. From these building blocks, the first prokaryotes began to form, that is, viruses and so on, coacervate drops, as they were also called.

— Is there a risk that meteorites will bring some form of life that Will it displace the earthly one?
– Of course, nothing can be denied. But so far, there is no 100% confirmation that at least some single-celled life was introduced using asteroids.
– So such life is still able to withstand high temperatures when entering the atmosphere?< /strong>
— They can be, for example, inside the body, which then, when it falls to the Earth, will split. The probability is negligible, but if there is a theoretical possibility, it cannot be denied.

– Do you take part in the creation of the Milky Way system?