The truth is out... 

via usmagazine.com When Mars was arrested in Las Vegas for possession of 2.6 grams of cocaine in September 2010, the "Grenade" singer told police it was his first time using drugs -- but as it turns out, that was a lie. 

"I don't know where that came from. I was really intoxicated. I was really drunk," he admits to GQ. "So a lot of that is a big blur, and I try every day to forget and keep pushing."

But when asked why he had a huge smile on his face in his mugshot, Mars gave a very honest response. "I have no idea . . . It was a picture," the artist explains.