However, as a side effect, a number of uncrewed probes – including the Viking program, Pioneer Venus project, "Mariner 10", "Pioneers 10" and "11", and the Voyager program – are cancelled so that their funding can be redirected to the crewed Mars mission, although another Mariner orbiter is sent to Mars to help prepare for the crewed landing. As a result, although humans walk on Mars, their knowledge of the Solar System, including Mars itself and especially the outer solar system planets which never get visited without the Pioneer/Voyager missions, is far less than in reality.