American astrophysicists Rebecca Martin and Mario Livio proposed model of formation of habitable planets, according to which the possibility of their existence is determined by the radius of the orbits of the gas giants in the system and the density of the asteroid belt.

Their report they published in the journal Monthly Notices of the Royal Astronomical Society, and its summary can be found on the website NASA. The authors analyzed the mechanism of the origin of the planets on the basis of data about the Solar system. Scientists noticed that Jupiter is separated from Mars and Earth asteroid belt, while the majority of external systems of gas giants are much closer to their stars.

Astrophysics suggested that this relative position of the asteroid belt and gas giant in our system may not accidental and is connected with the origin of life. To test this hypothesis, the researchers conducted a simulation of how the education of the inner planets like Earth or Mars depend on the motion of the gas giants. It turned out that if a gas giant with time very close to its star, then in the direction it gives to form smaller rocky planets.

Protoplanetary material in such a case is "undefined". However, if the giant remains on the same orbit, where he formed, its gravitational influence creates very dense asteroid belt that constantly bombard the inner planets, which destroys them all alive. According to the authors, there exists an optimal radius of the orbit, which should fall gas giant that the inner planets could appear and persist for life. Thus, according to the theory of American scientists to look for life now is only the planets of those star systems, where confirmed the presence of the same gas giant.

Of course, provided that the likely inhabited planet itself has about the same location as the Earth. In 2008, the American scientists have established that complex life forms on Earth - plants, animals and man - originated with a single event occurring 1.9 billion years ago.