Yes, there have been ET visitations. There have been crashed craft. There have been material and bodies recovered. There has been a certain amount of reverse engineering that has allowed some of these craft, or some components, to be duplicated. And there is some group of people that may or may not be associated with government at this point that have this knowledge. They have been attempting to conceal this knowledge. People in high level government have very little, if any, valid information about this. It has been the subject of disinformation in order to deflect attention and create confusion so the truth doesn’t come out. 
Edgar D. Mitchell, The Way of the Explorer: An Apollo Astronaut's Journey Through the Material and Mystical Worlds
aliens, astronaut, conspiracy, extraterrestrial, space