I remember an SG1 episode, they turned up on a planet which was a frozen wasteland for as far as the eye could see, no evidence of any life later than microbes.

Turns out the planet was earth - they were in Antarctica.

Clearly not comparable, but there's a big difference between salt flats in Namibia or the seater in Antarctica and landing in downtown manhattan or the Brazilian rainforest.

We've successfully sent half a dozen probes to mars, we've barely scratched the surface.