Edgar Rice Burroughs sent John Carter to Mars several times, but due to time-skew John landed on a fictionalized planet where the women were strangely attractive...
Curiosity landed on the real Mars, or rather Curiosity landed on a Mars that is inhabited only by machines. This Mars will cease to exist the moment a human sets foot on it.
However, to this day, no human has ever set foot on Mars. There are good reasons for that. One is that that human would probably not be coming back, another is that even getting there alive is really hard [citation needed].
It would also be very expensive, and you might say we have better things to spend our money on... However, as long as we are limited only to Earth, we're vulnerable. One decent sized rock falling out of the the sky and it is all over.
We're not quite ready to colonise Mars yet.
We really should be working on it more.
The Red Planet Blues
Ziggy played guitar,
jammin' good with Weird and Gilly...
There are no spiders
on Mars, spinning
in bone-cold canyons
to trap unwary space cadets.
There are no great domed cities, shining
pale in the brave red sunset. There are no get
of Edgar Rice Burroughs;
no green, six-limbed warriors
riding thoats or laying eggs
in odd moments
out there in the rusty desert. No Martians for the chronicler
to document their steady decline
after the Earthmen came.
Earthmen must come.
It is necessary.
Pick up the pickaxe.
Start digging a canal.
