Arealguy69: Ok i'll play devils advocate and say it didnt happen for arguments sake...
Now if it did happen, why hasnt it happened again since? we have better technology, more money etc...
I think it boils down to:
What would be the purpose for the mission?
Who is willing to pay the huge amounts of money to do it?
Is the money better spent on something else?
Do you want your limited technical talent working on this mission rather than something else?