No, but most believers don't need proof.
It is impossible to even speculate. There is no admitted proof that UFOs do exist and no hard information on propulsion.
There have been many people who claim to have witnessed both UFOs and aliens, however there is no proof available to the general public. If proof does indeed exist, it is held as confidential information by the government.
People have reported sightings of UFOs in France, but there is no proof of their existence.
The instant they are found they cease to exist. They are found and then they are identified. Once identified they cease to be UFOs.
Roswell Yes and Ufo's No
Extraterrestrial life forms-if they exist.
No accurate records exist.
No accurate records exist.
Yes.... People have seen UFOs.
There is proof of snow and Bacteria on Mars, but I'm not sure about the UFO's.
No accurate records exist.
I believe aliens might exist somewhere in the universe, but I don't believe any stories about UFOs or abductions or crop circles or anything like that. -------------------------------------------- A good answer. I don't *believe* in aliens because I have seen no proof of them, and belief without proof is faith (religion) not science.