Rare Earth Hypothesis

There may be more proof on the side of the "Rare Earth Hypothesis" - from the Oort Cloud:

The Oort Cloud is a spherical cloud of comets believed to lie roughly 50,000 AU, or nearly a light-year, from the Sun which places the cloud at nearly a quarter of the distance to Proxima Centauri, the nearest star to the Sun. The Kuiper belt and scattered disc, the other two known reservoirs of trans-Neptunian objects, are less than one thousandth the Oort cloud's distance. The outer extent of the Oort cloud defines the boundary of our Solar System.

Objects in the Oort cloud are largely composed of ices such as water, ammonia and methane. Astronomers believe that the matter comprising the Oort cloud formed closer to the Sun, and was scattered far out into space by the gravitational effects of the giant planets early in the Solar System's evolution.

The cometary membrane of the Oort Cloud and Kupier Belt actively feeds water to the interior planets, with some 20 to 40 ton water-ice comets hitting the earth's atmosphere 5 to 30 times per minute. Simulations show that Kuiper belt comets simply don't fall directly toward Earth's neighborhood but plod their way toward the inner solar system in stairstep fashion. It turns out that the massive outer planets are almost exactly spaced so that they "hand-off" comets from one to the other. At each step the powerful gravitational field of Neptune, Uranus, Saturn and Jupiter might either eject the comet from the solar system or pass it onto the next planet inside their orbit.