Radiation for one, but apart from that, in 2015 we don&#x27;t even go beyond low earth orbit and we&#x27;ll just have to wait and see but I&#x27;m guessing that no one will ever go to Mars.<p>No actual people have gone to Mars because its prohibitively expensive but also so incredibly unbelievably hard technically it will never happen.<p>Also undesirable. Why the heck would we want to colonise Mars? It&#x27;s a desert where we can&#x27;t live without life support.  It&#x27;s just sci fi to imagine we can or that it would be of value or sustainable. Earth is our home and will be forever.