No. We don't have technology to send undetected spacecraft to Mars. Amateur astronomers track everything that we send into space. Even the US Boeing X-37
It does secret missions into space and nobody is quite sure what it is doing there. But it is tracked wherever it goes, so we do know exactly where it goes and when. And it is too small for astronauts.
We'd know every step of any attempt at a Mars mission. For that matter though, it would cost hugely more than the robot missions they've sent there already and involve massive rockets like the Saturn V with present day technology. And there's no point in keeping such a thing secret anyway.