Bill Gross has some bad news for investors. In his June investment outlook released Thursday, the widely followed bond fund manager contended that bond and stock returns realized in the last 40 years are "a grey if not black swan event that cannot be repeated." Investors should not expect 7 percent returns on bonds or returns in the high single digits or double digits on stocks, Gross told CNBC on Thursday. "The markets are entirely different and it would pay to travel to Mars as opposed to stay on Earth, because the returns here are very, very low," the manager of the Janus Capital Unconstrained Bond Fund, said on CNBC's "Power Lunch".

Bill Gross Reuters

Gross said easy central bank policy could hold down bond returns. Central banks in Europe and Japan have adopted negative interest rates, while the U.S. Federal Reserve's target rate is at 0.25 to 0.50 percent. German and Japanese 10-year bonds currently have negative yields, while their 30-year bonds yield less than 1 percent. The U.S. 10-year Treasury note yield sat around 1.8 percent Thursday.