Honestly, I am opposed to sending humans to Mars, period. We shouldn't do it. It's unethical, a tremendous lapse of moral judgment just to stroke our collective egos.

There could be life on Mars NOW. There are bacteria that we know of on Earth, that if you transported them to certain locations deep under the Martian surface, would thrive. There are microbes that live in subterranean saline aquifers on Earth, and there are microbes that live in solid rock miles beneath the Earth's surface. There is no reason that these bacteria couldn't thrive equally well on Mars.

We know of Earth bacteria that could thrive under Mars's surface. Which means it is entirely reasonable to speculate that there may already be bacteria there filling that Martian ecological niche. But if we send people there...we risk contaminating it. We struggle to sterilize our rovers, but we do a pretty good job. But forget trying to sterilize a ship full of dozens of people. Our very gut bacteria are a contamination risk.

No, I think we should leave Mars the hell alone. And really, I think we have a very reasonable path forward for still producing very meaningful and important exploration of Mars. Look at how well robotics is advancing. Look at the recent Tesla event where they had all those robots wandering around, each remotely piloted by a human operator. THAT is the real future of Mars exploration.

I think we should simply wait on Mars until we've let remote presence robotic tech advance a few more decades. Then, you build such a robot that is durable enough to survive in an autoclave. You do send human to Mars, but they stay in orbit. The humans stay on a craft in orbit, and they remotely pilot humanoid robots on the surface to do the actual science work. This way, you can have exploration that has all the dexterity and flexibility of humans, as humans are able to pilot the robots in real time from orbit. And as an added bonus, your exploratory vehicles can be a lot simpler as you don't need to bring any crew or samples back from the Martian surface.

I think we could still exploit Mars as well. If we find that there is no surface life, well then setting up mining activities on the surface isn't a problem. If humans want to colonize Mars, we can build big orbital habitats from materials we mine on the surface. If, after a long period of study, we conclusively rule out the existence of Martian life? Well at that point we can start surface colonization by humans. Or, perhaps we discover a Martian deep-rock biosphere and fully catalogue it. Then maybe we discover that pretty much every terrestrial body has such a biosphere if conditions are appropriate. At that point, humans might decide that colonizing the surface with humans is worth the risk.

Anyway, I really do not support sending humans to Mars. We could potentially wipe out an entire biosphere, a biosphere that if it exists, could tell us remarkable things about how life arises and how common it is in the universe. We're only a few decades out from being able to do really good remote presence robotics. Let's just hold off on things until we can send humans that can get the full experience of being on the Mars surface, without actually being on the Mars surface.