Do you call it a secret when millions of people consider the evidence and believe and millions of other people refuse to consider the evidence fairly and/or refuse to believe regardless. It's a secret hidden in plain sight.
Water on the moon? Yes.
Water on Mars? Yes.
Signs of life on Mars? Probably.
Vast cities in plain sight on our side of the moon? No.
Too easy to see. One picture leaked, the whole thing unravels.
I haven't studied that sort of thing since it started coming out more publically. I had believed at one time in such on the dark side of the moon--so to speak--hidden from earth's normal view.