Extraterrestrial Highway, Nevada, USA
Extraterrestrial Highway, Nevada, USA is one of the most popular destinations for UFO tourism. stock.xchng

Former NASA astronaut Story Musgrave has been to space six times, so he has as good of a claim as anyone to being an expert on extraterrestrial matters. A large UFO gathering he is planning to address is eagerly awaiting his input, but they may be disappointed: while Musgrave believes firmly that aliens exist, he said that he has yet to encounter evidence they have ever visited Earth.

I'm going to tell them that, for me, and my interpretation of everything that's come my way, I cannot arrive at the idea that we have been visited -- either in the past or now, Musgrave told The Huffington Post as he outlined his plans for the 42nd annual Mutual UFO Network Symposium in Irvine, California.

Musgrave said that he has pored over the evidence, using his access to get as deep in the bowels of the military and the intelligence community as you can go, but found no evidence supporting contentions that aliens have been documented or that the government has covered up an encounter.

Some astronauts have been quoted as saying they think they're [aliens] out there -- I have seen their evidence, and for me, it's not evidence, Musgrave said. Other astronauts were not able to provide me with any empirical evidence, either.

The government has certainly looked into the possibility. The Federal Bureau of Investigation recently released a huge cache of documents detailing their dogged pursuit of purported UFO sightings, but what appeared to be flying saucers ended up being trash can lids.

The Mutual UFO Network meeting will feature nuclear physicist Stanton Friedman, former U.S. Air Force Intelligence Officer George Filer and other prominent UFO researchers speaking to the theme of ET Contact: The Implications for Science and Society. The organization's Web site describes it as a nonprofit devoted to resolving the scientific enigma known collectively as unidentified flying objects, dispatching investigators to look into alleged sightings.