The Ridley Scott movie that has just been released, that is a prequel to the first Alien film is a movie that introduces the moviegoer to the Space Jockeys and the Engineers that supposedly created life on this planet. In the novelization of the Alien move the alien race that landed on the planet were killed by the Xenomorphs and they left a beacon warning other alien races to stay away from the planet, but this had the unfortunate effect of luring the humans to the planet to investigate the signal. The books of the Alien films are better than the movies, this is true of any movie. I am not sure what type of propulsion the alien race was using that crashed on the planet, they used that huge seemingly living spaceship. To travel interstellar distances you really need some kind of technology that can fold space, otherwise it would take millions of years to travel to another star. The nearest star to us is about 4.22 light years away, one light year is 9.4607×1012 kilometres and that multiplied by 4.22 is a huge number indeed.
The nearest and best candidate for a star with an extrasolar planet capable of harbouring life is Gliese 581 g, this is 20.5 light years away from Earth. This would take a formidable time to reach with current rocket technology, even the Voyager 1 probe is only travelling at about 33,0000 miles per hour and will encounter the boundary betwixt the solar wind & interstellar material in the year 40,000, and another star system after that in the year 299,000. But the shield of radiation around the solar system may impede reception of any signals sent after Voyager 1 leaves us for good. We have been sending signals into space for a long time from television and radio signals as well as radar signals, but signals like television and radio would be too spread out and weak to be picked up by interstellar intelligences. Unless they built a radio telescope that was the size of a solar system. But the fact is that the signals degrade after time and it is not likely that D,Gark and T,Murlk sitting in front of their television set tuning in signals from Earth 30 light years away would not see anything at all. Heaven help humanity if they saw modern television. What would interstellar intelligences think of Jersey Shore or Hogan Knows Best?
The Voyager probe only has power to last until 2025, this means that it will not be able to send back any details about space after the passage through the heliopause very soon. But it would still be carrying the golden record and the plaque with information that could lead an alien race to Earth. In the movie “2001”, this theory was put forward that showed an alien race that had ascended beyond skin and bone coming to Earth and helping the primitive ape inhabitants of the Earth learn how to use tools and kill animals for food. This also taught them warfare and violence, but this ascended the apes into more advanced forms of life. There are many legends amongst human cultures that speak of aliens that came to Earth and helped the people with advanced technology before leaving again. This could be true. Who knows how life truly originated on this planet, the theory that it was seeded with life by an alien race should not be discounted. The first life on Earth was in the oceans as the atmosphere at that time 600 million years ago was poisonous to life. But over time that atmosphere changed into the modern oxygen atmosphere that we breathe. If all life on the Earth is descended from something that aliens placed on the planet, it must have been seeded here about 2 billion years ago or more.
This is not impossible, the universe is so large and populated, that it must have very old and advanced races that are far ahead of us and had interstellar space travel before life on the Earth existed. Obviously they would have visited the Earth after the cataclysmic impact that created the Earth`s moon, this was an impact that involved an impactor that was the size of Mars and would have been so severe that the Earth`s crust was melted. Any life on the planet, although implausible back then would have been vaporised. This could be how the Earth`s iron core came to be. With all of the planets that we are discovering out in space and the many discoveries of extremophiles on Earth that can live in horrible conditions like the fish that live in sulphuric acid and life forms that live around black smokers on the bottom of the ocean in water hot enough to melt lead, it extends the range of planets that could have life. Even Jupiter could have life floating in the clouds perpetually floating with no land to walk on, only endless clouds. So the idea that the Space Jockeys could be out there somewhere is not implausible at all. Even a hot planet like Venus with a runaway greenhouse effect and a surface pressure equal to one kilometre deep in the oceans with a surface temperature of 480 degrees Celsius could have life in the clouds where it is cooler, even though they are concentrated sulphuric acid.
That is the definition of an extremophile, a lifeform that has adapted to a harsh environment. There could be planets like Tatooine that are all desert and they could have a climate that is not too hot or cold and could have lifeforms living underground. That is not impossible, but I do wonder what those huge Bison like creatures on the drifting Dune seas were supposed to be eating, but I guess there are other lifeforms on the drifting sands that they subsist on. Actually these are the Banthas, they are indigenous to Tatooine, and they eat grass and other plants. http://starwars.wikia.com/wiki/Bantha. Any space faring civilisation would have travelled a very long time if they have come to Earth. Speaking of strange alien life, what about the giant sphere that was feeding off the Sun before flying away at an impossible speed, fighting against 28 times Earth gravity. http://www.securitronlinux.com/bejiitaswrath/strange-sphere-feeding-off-the-sun/. This is a true mystery, Commander Data as Sherlock Holmes would have a good time solving this mystery. How could it survive the 6000 degree Celsius temperature of the Sun and fly away without any perceptible effort.
The fact that the Earth recovered after the impact that created our Moon, is outstanding; it goes to show that our planet and the life on it is very resilient, we survived the last ice-age and we can survive the next one if it comes. if we could build a base on the Moon and colonise Mars we could survive longer as a race, if we stay on this planet and never go anywhere else, then we will die out one day. Colonising Mars would take a lot of effort, but it would be worth it. Thickening the atmosphere by focusing the Suns rays onto the poles to vaporise the dry ice would create a thicker and warmer atmosphere. We could even colonise Saturn`s moon Titan, as described in the book 2312.