I'd be very surprised. First, I don't think we are going to send humans to the Mars surface any time soon. The reason is that we are looking for life on Mars both past and present. All the higher latitudes of Mars - the regions with ice on or near the surface - are marked as special regions on the map (regions where present day life on Mars might be possible) as are some spots in equatorial regions:
All the regions above and below the dotted lines are marked as special regions needing Viking level sterilization or higher, and the new equatorial dark streaks are as well. Curiosity could not land in any of those places. So a human occupied spacecraft which can't be sterilized even to Curiosity standards, nowhere near, can't go anywhere near these regions.
For present day life we are probably looking for nothing more complex than a microbe, or perhaps a lichen. But extremophiles on Earth can survive in conditions similar to ones that may exist on Mars. There's increasing evidence for presence of liquid water on Mars in small quantities, just below the surface - very salty - but still with some potential that it could be habitable for some forms of Earth life. Also some Earth lifeforms can survive in Mars simulation chambers and even photosynthesize and grow even without any water, just using the 100% night time humidity in its cold thin atmosphere.
Any life on Mars, including microbes and lichens, would be a major discovery, and especially so if it is different in some fundamental way. That could include different biochemistry (e.g. RNA only, smaller more primitive cells, not yet evolved to DNA), different cell machinery, even similar to Earth life in all respects except a different way of supplying energy (something different from our mitochondria), or a new form of photosynthesis, or anything new in the complex workings of cells.
The very last thing we want to do is to introduce Earth life to Mars at this stage. Our experiments we could send to Mars are so sensitive that they could detect a single amino acid in a sample. Earth life could make present day Mars life extinct (especially if it is a simpler earlier form of life), and even if it didn't, it would make it very hard to study.
Generally agreed that the very last thing we want to happen is to go to Mars only to discover life we brought there ourself.
So, I can't see an international body of astrobiologists ever approving a human mission to the Mars surface at our current level of understanding. They would surely just say "more research needed" as they have said every time they've been asked to debate this so far. They'd be professionally responsible for affirming that it is safe to send humans to Mars for planetary protection, that would be the point in it - and how could they be sure of that?
And returning a sample from Mars with no life in it would prove nothing. Return samples from the core of the Atacama desert, and if you don't know exactly where to look, they probably won't have life in them either. And a lifeless Mars also would need to be protected if it has habitats for life, so we can study how a terrestrial world works when it hasn't got any life in it. Whatever we find on Mars, the nearest other planet resembling it is surely light years away around another star, so it's not a "throwaway planet" we can blindly drop Earth life onto to see what happens. And doing that anyway is not an experiment. An experiment needs a hypothesis to test, a control etc. Accidentally dropping life on Mars with no plan behind it, is just mucking about.
Some people have suggested that it might be possible to land humans in the equatorial region of Mars and then send sterilized automated rovers from the base to regions of special interest to find samples for them to study.
But Mars is a connected planet, with its global dust storms. And the dust storms cut out most of the sunlight and the iron oxides in the dust would protect any imbedded spores from UV light. So, with trillions of spores surely scattered around the human occupied base - escaped from airlocks, from spacesuits (designs leak constantly) vented air from the habitats, probably human wastes also - how can you guarantee not to contaminate Mars?
But the worst thing is, that there's going to be a reasonably high chance of a crash on Mars, bound to be. It would be a risky thing to send humans there. The seven minutes of terror landing is the most risky part, but there are risks earlier also, such as the insertion burn.
So how can Mars be protected in the event of a human occupied ship crashing there? Especially if it involves a failed insertion burn, maybe one that goes on for a little too long, resulting in them hitting anywhere in the equatorial regions of Mars? They could hit one of those special regions - especially since the aim would be to land the base close enough to a special region such as the warm seasonal flows, to study it remotely.
So, it seems obvious to me that the first human expeditions to go to Mars will be to Mars orbit, not to the surface, especially if it is done as soon as the 2030s. I think that this will turn out to be the only kind of expedition that could be approved internationally at current stage of knowledge. Far safer for the crew also, as you don't have the landing on Mars and can explore the surface telerobotically from orbit, or from its moons Phobos or Deimos. And you can get back to Earth far more easily.
I think it would also be a "ballistic transfer orbit". This is a special recently discovered type of orbit which gets you into orbit around Mars with possibly no insertion burn at all. If you launch it from Earth on the right trajectory, then it ends up just in front of Mars as Mars catches up, a long distance from Mars, and gently falls into a Mars orbit.
Eventually after a few whirls around Mars, it would fall out of that orbit just as easily as it fell into it - but you then start lowering its orbit with ion thrusters. Whether it saves any fuel is dubious. There is less fuel for a distant orbit as you save on the insertion burn, but not less fuel if you want to get close to Mars. But it does have the advantage there is no all or nothing insertion burn. Instead like the Dawn spacecraft, very gentle process, gradually go down to lower orbits.
This has huge advantages for planetary protection as there is almost no chance at all of your human occupied spacecraft hitting Mars by accident. And the lowering of orbit is done by the much more efficient ion thrusters. So there might be a saving of mass there, and at any rate, not going to be hugely more fuel than a more conventional Hohmann transfer orbit. It has other advantages too, as you can do this type of transfer at any time, no matter what the relative positions of Earth and Mars, not just once every two years as for Hohmann transfer.
And Mars from orbit looks homely, like Earth. I think that would help psychologically, very like orbiting Earth from the ISS.
And you'd get more science done that way. Depending on the orbit, one possibility is this one:
One Orbit Flyby, Time 100x: Mars Molniya Orbit Telerobotic Exploration in HERRO Mission Proposal
You come close to Mars twice a day on the sunny side every day as it is a sun synchronous precessing orbit. Result is that you see the entire surface of Mars in full sunlight every day. So can control robots anywhere on the surface of Mars in full sunlight with close up telepresence at least once a day.
I think that's one of the most likely first human missions to Mars, because it's also a fuel efficient orbit to get into, similar to Mars capture for the insertion burn. It would be equally easy to get into with ion thrusters and ballistic transfer. And has a good pace to it, every twelve hours you are close to Mars, can explore it with telepresence, do experiments with robot avatars on the surface with hand eye co-ordination, binocular vision and haptic feedback (you can feel the things you touch). Also with streaming HD video and telemetry of everything you do so people back on Earth also can look at everything you saw, and maybe spot things you didn't. It would be a very involving mission therefore as well, and good for citizen science.
Another likely first mission is Robert Zubrin's "double Athena"- the idea is you do a close flyby of Mars, which then puts you into an almost Mars like orbit, you shadow Mars for half its orbit, so about one Earth year, gradually getting further from it, then back to it, then another flyby sends you back to Earth. It's a good mission profile, total only 700 days. And it doesn't have an insertion burn, because you do a double flyby, not an insertion into Mars capture orbit. And is very safe, it's a "free return" mission. So long as you get on the right trajectory, when you leave Earth, you are already on the right trajectory to get back to Earth 700 days later. Only minor course corrections needed from then on. So that also seems pretty safe for planetary protection too, without the problematical insertion burn of Hohmann transfer.
Inspiration Mars is also a "free return" mission but with one flyby only, and leaves Mars quickly, so gives you only hours of close up telepresence for Marss, requires a flyby of Venus on the way back, which is a bonus, but again not much time in vicinity of Venus, and has a far faster return to Earth so it's more of a challenge to shed that speed when you get to Earth in the Earth's atmosphere or however it is done. But the advantage of only 500 days instead of 700 days. But if we are at the point where 500 days is thought to be far safer than 700 days I think we are sailing too close to the edge for human safety, taking too many risks. I think we should do either only once we are confident we can do multiyear missions sasfely. There is enough to go wrong anyway, it's dangerous enough anyway without doing missions that are stretching human survivability to the limit.
So - any of those missions are far easier than a mission to land on the surface of Mars, so could be done sooner. Still, I'd be astonished if we can do any of them by the 2030s, unless we can find a way to get to Mars in days or weeks rather than months. Because for decades we've been shuttling back and forth from LEO, with lifeboats always attached to the space stations that can take our astronauts back to Earth within hours.
I think it is enough of a big step forward to go to the Moon, where it would take two days to get back to Earth in an emergency. Two days is a long time in an environment where there is no air to breathe except in the spaceship. The Apollo astronauts may have made it seemed easy but it was extremely hazardous and only worked because they were well trained, and also experts able to be calm and collected in emergencies. The likes of you and me would probably have died in the Apollo 13 situation (unless you happen to be a trained astronaut or jet pilot or similasr) just panicking and not communicating clearly with Houston etc. Or indeed the lunar landing itself, the first one especially, you'd need to be very skilled and cool and collected also to do that.
If we go back to the Moon, as ESA plans to do and maybe USA will join in in the future (at present they are restricted in what they can do by Barrack Obama's declaration that USA will go straight to Mars and not go to the Moon first) - it's still a hazardous place for humans. We'd have to deal with the extremely cold lunar night, for 14 days. We'd have to learn to be able to rely less and less on supplies from Earth because of the expense of sending supplies to the Moon. And there is lots to find out there. We have reached the stage of the early Antarctic explorers so far, who had got as far as landing a few parties on the coasts of Antarctica, but not yet sent anyone to explore the interior. Our next expeditions to the Moon would be like the first missions to explore the mountains and interior of Antarctica. There's lots to discover there. We can't do it all from orbit around the Moon.
Once we have the ability to keep people on the Moon for a couple of years at a time with no resupply from Earth, and solved problems of reliable closed systems (which we don't have yet on the ISS) and growing their own food - then we may be ready for interplanetary missions. But I wouldn't be surprised at all if there are many surprises and things to fix before we are confident with lunar long term missions.
Right now, no astronaut has ever spent as much time in space as would be needed for a mission to Mars and back. And though one cosmonaut has spent fourteen months in space, and returned to Earth remarkably healthy, that's Valeri Polyakov, that's still way short of two and a half years - and he could be an outlier case. One person surviving in space for fourteen years doesn't prove that everyone will survive at the end of a two and a half year voyage. For more on this, see Robert Walker's answer to What is the longest time an astronaut can spend in space before it is too hard to re-acclimatize to Earth?
I'm sure that can be solved. Apart from anything else, we can use artificial gravity, with either a tether spin, or short arm centrifuges, depending on which works best, to deal with perhaps all the problems of zero g.
The other thing that could make it possible is if we find some very fast way to get to Mars. It would be much easier if we could get to Mars and back again within a month, for instance, instead of it taking getting on for two years, or more than two years if you spend any time in the vicinity of Mars.
A mission to a place that is one week of travel away from Earth would be a reasonable next step after a mission to the Moon. But a mission to a place that is in worst case two years travel away from Earth seems a step too far.
I think it is possible by the 2030s to go to Mars orbit, but I'd be astonished if we do get to that point by then. Pleasantly surprised. Could happen through either
- Developments in rocket technology permitting very short travel times
- Or, that we quickly discover how to keep humans alive and healthy in space conditions for years on end without resupply from Earth
- Or, that it gets really cheap to send hundreds of tons into orbit, so we can consider just throwing the mass at it - send hundreds or thousands of tons of supplies to Mars orbit to sustain our crew. Then we could have an ISS style mission in Mars orbit.
In the last case we do need to be especially careful as regards planetary protection that we are just as careful for every one of the perhaps dozens of supply missions to Mars orbit before we send the first human missions. You'd send the supplies in advance, just as for the surface. Make sure you have at lest two spaceships in Mars orbit fueled up and ready to return your astronauts to Earth before you send humans there. But even then it is a bit risky, as we've had some close shaves with the ISS that were saved because it was easy to resupply to it from Earth.
Even sending loads of supplies in advance, it's not guaranteed that you send the right things. If for instance the problem is some component that is not suited for purpose, then having three copies of it might just mean three things that don't work. Like the reaction wheels, the early reaction wheels that started to fail, and they had backups but those also failed. We don't want our Mars expedition to have to rely on unproven technology like that.
So, needs care, and to go one step at a time. That was the key to success for Apollo. If they had just sent a mission to the Moon right away without the Gemini and Apollo series of missions, it might have worked, but there would have been a good chance ofd it failing. Even Apollo 10 which went nearly all the way tothe surface of the Moon but then went back to Earth without ever landing, turned up an issue that would have probably killed the crew if they had landed.
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