Roswell UFO crash which shocked the whole world , Why did Milatry Hide it 

Nick Pope, who investigated the UFO phenomena for the UK MoD until 2009, says he and the Roswell Daily Record newspaper believe someone can come forward to confirm once
and for all whether an alien space craft did crash in the New Mexico desert in 1947, before the greatest cover up on Earth began.
Roswell has been at the heart of the UFO scene since in July 1947 the military sensationally announced in a press release it had found the remains of a crashed flying saucer in the
desert nearby.
Local paper, the Roswell Daily Record, wrote this up as the lead story, under the headline 'RAAF Captures Flying Saucer on Ranch in Roswell Region'. 
But the following day military officials retracted the statement, saying it was in fact a damaged US Air Force air balloon, prompting claims of a cover up.
"As we approach the 70th anniversary of this much-debated incident, the Roswell Daily Record is launching a campaign to resolve the mystery for once and for all. 
"To do so, we need your help.
"While people argue to this day about what happened at Roswell in the summer of 1947, nobody disputes that something crashed. That’s because far from denying this, the military
authorities actually helped get the story out — at least at first."
The original press statement said: "The many rumours surrounding the flying disk became a reality yesterday when the intelligence office of the 509th Bomb Group of the Eighth Air
Force, Roswell Army Air [auth] Field, was fortunate enough to gain possession of a disk.” 
Witnesses later came forward to say there had been alien bodies within the "crashed craft", which along with the wreckage were then taken away.
The newspaper's campaign is now calling on anyone who "hung onto" a part of the crashed object at the time to come forward with it for testing.
Mr Pope blogged: "As every citizen of Roswell knows, the city is at the centre of one of the greatest mysteries of all time.