There may be several.
Astronomers decided to conduct a computer simulation to potentially the possible destruction of our Earth. It turned out that there may be more than a hundred.
Talk about how our planet will die and the Solar system, excite the minds of scientists for a very long time. The most popular theory is a model of nice. It lies in the fact that the expansion of the Sun and convert it into a red giant, the orbit of the planets will change, and it is in danger of collision objects. Also not excluded the option, when the Sun just will increase to such large sizes and will take along the terrestrial planets, and then other.
Unable to face Mars, Earth and mercury. Mercury is quite able to meet on its way to Venus, since the total displacement of Jupiter and the first planet in our system will cause variations in the trajectories of the spins. By ricochet may suffer and Earth.
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Before the collision of Earth and Mars, the second is quite able to be outside the Solar system. Whatever it was, but with a large number of repetitions of computer experiments a model of nice has become the most plausible.