Presently, mankind is aware of 60 thousand asteroids. A thousand of them are found dangerous to the Earth. They started tackling this problem seriously just a short while ago. First, science fiction writers nicknamed the threat from space the "hammer of the Gods", then scientists began to estimate the probability and consequences of the impact of this "hammer". The results of calculations have horrified not only astronomers, though the traces of previous impacts have always been before the eyes of the people. According to a version, it was a collision with an asteroid that caused global changes of the climate and, as a consequence, extinction of dinosaurs about 65 million years ago. The amassed scientific knowledge has brought to a conclusion that we are not guaranteed against the recurrence of a similar disaster. In 1994, in the Russian Federal Nuclear Centre (town of Snezhinsk) they held an international conference "Space Security of the Earth", at which they set up a scientific and technological foundation "Space Shield" (for further information please refer to www.spaceshield.ru or www.snezhinsk.ru/asteroids/index.htm). In the autumn of 2000 in Yevpatoria, the Third International Conference on Space Security of the Earth was held.
So, what will happen if an asteroid or a comet hits our planet? "... A comet with a diameter of less than 100 meters will explode in the upper layers of the atmosphere and, in all probability, cause no damage", — believes David Morrison of the NASA research centre. "If a comet is 10 or more kilometres in diameter (when the impact releases the energy roughly equal to that released in an explosion of 100 million megatons of TNT), the consequences of such impact will be fatal: living organisms will die out on a large scale and most of the forms of life will be lost".
Astrophysicist and radio astronomer from the Rodos College in Memphis Gerrit L.Vershuur, referring to the results of a computer simulation, draws an apocalyptic picture: "...Collision with an object of about one and more kilometres in diameter will apparently bring the civilisation to ruin. The impact of such space object will not wipe out humankind as a species. But if the diameter of an asteroid exceeds 5 kilometres, it is improbable that the Homo sapience species will survive on the Earth. At the moment of the impact, there will emerge a huge burning ball that will destroy everyone who happens to see it. Then the explosion products (melted and red-hot pieces of rock) thrown into space, will start falling on a vast area — half of the global surface — as blazing fragments. (We watched something similar when the Shoemaker-Levi comet hit the Jupiter in 1994). An innumerable number of meteorites will fill the skies, and a rain of particles, burning down in the air, will pour to the ground... The heat, released by such rain, will incinerate forests and cities. Dust and smoke will cover all the sky, thus plunging our planet into the so-called "post-impact winter "...
According to the simulation results, the impact of an object of 10 kilometres in diameter will plunge the Earth into darkness for almost a year. Photosynthesis will terminate, plants and animals will die. The few survived will be destroyed by acid rains (sulphur dust and nitric oxides are formed as a result of a comet explosion), the ozone layer will be destroyed by nitric oxides and red-hot rock particles thrown by the explosion into the stratosphere. Winter will set in everywhere, after which a new cycle of life will possibly develop, but without us.
For the readers not consider the above a New Year dread story, I will add the following: from 1991 through 2000, four asteroids passed by the Earth at a distance not exceeding 0.45 of the distance to the Moon, one of them passing at 0.28 of this distance. An asteroid is regarded as potentially dangerous when it is at a distance not exceeding 20 distances between the Earth and the Moon and has a diameter not less than 150 meters... By the way, if the Tungus meteorite (1908) had exploded not above a deserted taiga but, for example, above London, the city would have been destroyed within the diameter of the London М25 ring road (the conclusion arrived at by the British scientists from the Special Group created by the government to study the problem).
The UN, the Council of Europe, the NASA, the European Space Agency, the Federal Nuclear Centre of Russia and the governments of many countries have noticed this problem. Many research centres in the world are studying it intensively. At the conference in Yevpatoria, they debated an idea of influencing dangerous objects (certainly, after they are detected, which is a problem in itself, and a thorough examination is carried out) by a nuclear explosion, a kinetic impact or a laser beam. The technological potential is already available for humankind to create a reliable space shield: for example, the "Dnieper" missile (known in the West as "Satan") can be used to destroy dangerous objects or correct their trajectory. At the conference in Yevpatoria, representatives of the S.A.Lavochkin Scientific and Production Association (SPA) put forward a programme of conducting a research experiment code-named "Space Patrol". The Crimean Astrophysical Observatory, whose optical telescopes are powerful enough to see an object of 1 meter in diameter at a distance of 330 thousand kilometres, and representatives of the "Space Shield" foundation (Snezhinsk) will take part in the experiment. The Yevpatoria radio telescope is also planned to be used. The point of the experiment is to detect small (1-2 meters) space bodies, which are regularly approaching the Earth. Astrophysicists are to select an object and to perform targeting, whereas the Lavochkin SPA is to deliver a "space interceptor" to it. It is necessary to start practical activities as soon as possible to find out our real potential. But in the meantime, scientists state that the world community is not adequately aware of the scope of the global threat coming from space, which affects the finance of the relevant projects. "Today mankind is facing a dilemma: to incur inconsiderable expenses (to the tune of several hundreds of millions of US dollars a year) and to build a system of space security, or, relying on a chance, to postpone this decision till the nearest (probably the last in its history) catastrophic collision", — read the "Recommendations" adopted by the Yevpatoria conference. Scientists propose to develop and introduce a tracking system comprising two or more space-based telescopes, two-three land-based support telescopes, radar aerials. It would be proper to expand the programmes of exploring small space bodies, which are carried out by the Crimean Astrophysical Observatory and other observatories in Ukraine and Russia, with special attention paid to the tasks of tracking and studying the properties of asteroids and comets. They also suggest other actions which should not be delayed: already on December 16, 2001, asteroid 1998WT24 will be passing by the Earth at a minimum distance of 0.0104 astronomical units. Scientists recommend that it be paid a priority attention and a radar research be carried out. But it cannot be excluded that a certain object, unidentified so far, will meet with the Earth long before that and then any research will be the last thing the people will think about, as an effective system of tracking dangerous space bodies is not created yet.