He is all for it; He jokes around about it and doesn't care for ladies; He teases him and jokes around with him; That Romeo doesn't care what Mercutio says. Hope this helped!
It would increase dramatically the risk of forward contamination of the Mars surface with our earthly microbes, which would ruin our unique chance to study a pristine Mars.
All the reasons advanced to vindicate the act of Humans traveling to Mars are either wrong or can be addressed in a way that spares Mars.