Scientists from the Max Planck Institute for Astronomy have identified the frequency rise asteroid threat. According to them, the risk of a serious accident increases. While there is a slight but steady increase in the number of asteroid impact during the last 250 million years.
Powerful impacts of comets or asteroids have caused several mass extinctions of animals on Earth. Best known dinosaurs 65 million years ago. Today found about 200 craters, some of which are hundreds of kilometers in diameter, indicating that vast scale disasters. Understanding how the collision with the passage of time, is not only an academic question. It is vitally important knowledge that determines the risk of catastrophic collisions of large bodies with the Earth's surface.
Barringer Crater in Arizona, has a diameter of 1265 m and was formed by meteorite with a diameter of about 70 meters, however, even this, far from the size of a large asteroid, a heavenly body can destroy a big city
Since the mid-1980s, some scientists have argued that they were able to determine the periodic changes in the incidence of falls of asteroids and comets. In their view, the study of the craters, in particular of their age, provides a statistical pattern, such that the next disaster. Usually these periods range from 13 to 50 million years.
One explanation for this periodicity associated with the movement of our solar system relative to the main plane of the Milky Way galaxy. This can lead to gravitational perturbations caused by neighboring stars, which change the orbit of asteroids and comets in the cloud on the border Horta solar system.
But perhaps the most popular "mystical" explanation — is the existence of an unseen companion star of the Sun, called Nemesis. It moves in a highly eccentric orbit, periodically converging with cloud Horta and sending asteroids towards the Earth.
Scientists from MPIA not seeking undiscovered cosmic phenomena, and focus on statistical research, describes the rate of incidence of large celestial bodies on the Earth. That is why we use the alternative method of estimating the probability (Bayesian statistics), which avoids many of the pitfalls that hamper traditional analysis of meteorite craters. Scientists have discovered that simple periodic oscillations can be excluded with certainty. Instead, there is a general trend in the period from about 250 million years ago to the present, the number of strokes, judging by the number of craters of different ages, has been steadily growing.
There are two possible explanations for this trend. Thus, small craters are destroyed faster, while the large leaves traces on the surface of the Earth for millions of years. Thus the trend may simply reflect the fact that larger and younger craters it is easier to find than the small and old. In particular, if we look only at the craters greater than 35 km and less than 400 million years, are less affected by erosion, the tendency to increase the number of strokes was observed.
On the other hand, the trend can be very real: the analysis of impact craters on the Moon, where there is no natural geological processes leading to the erosion of craters, clearly point to the reality of growth trends asteroid threat.
Reason for the existence of this trend is unknown to scientists, but it is safe to delete the threat of the mysterious invisible nemesis, because there is no evidence of its impact on the periodic asteroid bombardment of the Earth.