We need to invest money and go there to discover any life there might be there. Probes aren't going to cut it. If there is life its tenuous and holding on in sheltered locations not on the wide open flat plains our probes land on.

His explicit mission was a failure. Instead they discovered something beyond their wildest dreams that turned Spain into a world super power. The reasoning for going doesn't matter, its what you discover after you are there and how you make use of it that matters.

Columbus traveling to the America's was an expensive sink also. You cant judge the results of exploration and expansion before its happened. You have no idea what might come out of pushing to Mars.

> but its expensive to return that to earth

Who said anything about coming back? Colonization is gong to stay. Elon doesn't care about Earth orbit construction. He wants to live on Mars.