( CNN ) -- Earth Day may fall later this week , but as far as former NASA astronaut Edgar Mitchell and other UFO enthusiasts are concerned , the real story is happening elsewhere . Astronaut Edgar Mitchell , shown after his Apollo mission in 1971 , claims there `` is no doubt we are being visited . '' Mitchell , who was part of the 1971 Apollo 14 moon mission , asserted Monday that extraterrestrial life exists , and that the truth is being concealed by the U.S. and other governments . He delivered his remarks during an appearance at the National Press Club following the conclusion of the fifth annual X-Conference , a meeting of UFO activists and researchers studying the possibility of alien life forms . Mankind has long wondered if we 're `` alone in the universe . [ But ] only in our period do we really have evidence . No , we 're not alone , '' Mitchell said . `` Our destiny , in my opinion , and we might as well get started with it , is [ to ] become a part of the planetary community . ... We should be ready to reach out beyond our planet and beyond our solar system to find out what is really going on out there . '' Mitchell grew up in Roswell , New Mexico , which some UFO believers maintain was the site of a UFO crash in 1947 . He said residents of his hometown `` had been hushed and told not to talk about their experience by military authorities . '' They had been warned of `` dire consequences '' if they did so . But , he claimed , they `` did n't want to go to the grave with their story . They wanted to tell somebody reliable . And being a local boy and having been to the moon , they considered me reliable enough to whisper in my ear their particular story . '' Roughly 10 years ago , Mitchell claimed , he was finally given an appointment at Pentagon to discuss what he had been told . An unnamed admiral working for the Joint Chiefs of Staff promised to uncover the truth behind the Roswell story , Mitchell said . The stories of a UFO crash `` were confirmed , '' but the admiral was then denied access when he `` tried to get into the inner workings of that process . '' The same admiral , Mitchell claimed , now denies the story . `` I urge those who are doubtful : Read the books , read the lore , start to understand what has really been going on . Because there really is no doubt we are being visited , '' he said . `` The universe that we live in is much more wondrous , exciting , complex and far-reaching than we were ever able to know up to this point in time . '' A NASA spokesman denied any cover-up . `` NASA does not track UFOs . NASA is not involved in any sort of cover-up about alien life on this planet or anywhere else -- period , '' Michael Cabbage said Monday . Debates have continued about what happened at Roswell . The U.S. Air Force said in 1994 that wreckage recovered there in 1947 was most likely from a balloon-launched classified government project . Stephen Bassett , head of the Paradigm Research Group ( PRG ) , which hosted the X-Conference , said that the truth about extraterrestrial life is being suppressed because it is politically explosive . `` There is a third rail [ in American politics ] , and that is the UFO question . It is many magnitudes more radioactive than Social Security ever dreamed to be , '' Bassett said .
He believes governments are concealing evidence that extraterrestrials exist . The man is from Albuquerque , New Mexico , the site of an alleged plane crash . Mitchell : The residents ` ` ' not to talk about their past '' by military .