There is no generally-accepted evidence that this occurred. The "alien visitors" theories concerning UFOs and alleged abductions are scientifically unsubstantiated. It is possible that non-intelligent lifeforms may have reached Earth in the form of organic material thrown into space by collisions of other planets or stars.
Scientists say that life can be expected to have evolved on other planets, wherever the environment is not so hostile that life can not be supported. They say that in this vast universe there must be many such planets that can support life and that some are likely to support intelligent life forms even more advanced than humans. Whether we believe that our God created the life on other planets is a matter of human faith. No doubt any intelligent life on other planets will never have heard of Earth's gods.
earth is the only planet known to house liquid water and life
It is important in case there is life beyond Earth.
The biggest reason is water. Astronomers think maybe there really may be traces of water or ice on other planets, but Earth has an abundance, perfect for us. Also, many other planet's living conditions are not suitable. Some planets have EXTREMELY hot hot hot or coooollllddd ccccoollllddd weather that we could not live through. There is not fertile soil or animals to eat (we probably wouldn't be eating aliens :P ). And atmospheres aren't as nice, no substantial protection from the sun's rays and gravity not as strong. There are also some more detailed answers but these are mostly the main ideas why the Earth support life when other planets cant.
Because (as far as we currently know) Earth is the only planet in our solar system that supports life.
Earth's scientist have not found life on other planets to date.
Yes, only on the Earth. We don't know if the other planets have life
Astronomers have found Earth-sized planets in other solar systems.
There is life on other planets. Imagine, there are 1000 planets in the Universe for every grain of sand on the earth. That's how many planets there are, so scientifically, the chance that there must be life on other planets as well is much greater than the chance that there is no life.
Other planets do not have water nor life
Fortunately for the other planets, Earth is the only one.
Because Earth is the only place where we can murder the English language and ask questions like, "Why life is possible only in earth not in other planets?"
ALL OF THeM!! But seriously: We know of no planet except Earth with life on it in our solar system, and the conditions on other planets forbid advanced life. There are planets belonging to other suns, but they are very far away, and we have no information about life on them. It is extremely unlikely, but not impossible, that aliens from other solar systems have visited our solar system.
earth has air , water and life.
No, there is no oxygen on any other planet other than Earth because there is no planet life on the other planets.
We don't know about any other other place, besides Earth, that harbors life. But many scientists think that there is life on other planets.
Other than the Earth, no life has been found on any of the other planets. We are still searching.