I don't think it's a given that anyone will, to the Mars surface. We don't have to put a human on Mars, now, or ever. We could send humans to Mars orbit or to Phobos or Deimos for instance.
So many news stories and announcements treat it as a given that we have to send humans to Mars. But I don't think it is. We can explore the ideas sure. They are fun ideas that appeal especially to science fiction geeks and movie goers who have seen or read so many fictional stories about humans on Mars. But are they the best ideas to motivate our near future space explorations?
There's another side to all of this which doesn't get nearly as much publicity. And it is seldom covered in the science fiction about Mars.
The main reason why we might hold back from sending humans to the surface right now is to protect Mars from Earth life. Just as we hold back from sending humans or even automated subs into lake Vostock below the ice in Antarctica.
It depends what we find out about Mars. For instance if we find Mars has its own indigenous life, even microbes, we might decide not to send humans to the surface, quite yet or even never, if we determine that Earth life will make Mars life extinct.
There are many possibilities there which might lead us to conclude that:
For instance, if the Mars life is more primitive than Earth life, using RNA only and cells a tenth of the size of the smallest Earth cells, the more advanced Earth life could take over from it if introduced.
Or if the life has the same origin then Earth life could mix its genes with Mars life via gene transfer molecules, or could take over from Mars life in some niches etc. That would make it far harder to study Mars life. Right now, if we find even amino acids with a chiral imbalance that's consistent with life, especially in a potential habitat for life on Mars - it would be a strong indication of the presence of Mars life. Introduce Earth life and then a discovery like that would not necessarily mean Mars life, your first assumption would always be that it's the introduced Earth life.
And if Mars life say split off from Earth life in the early solar system, more than three billion years ago - well the gene transfer mechanisms are so ancient, it's well possible that it could still share genes with Earth life meaning you end up with hybrids that are neither Earth or Mars life - something that the archaea can do with surprising ease.
Or if Mars has no life at all, we may decide it is our only opportunity to study an Earth like planet without any life on it.
To send humans to the Mars surface, especially if there's a risk of a hard landing on a "special region" - regions thought to have a possibility of habitats for Mars life in them - this could close off many possibilities for all future time. We just don't know enough about Mars yet to do an irreversible decision like that.
And different areas of Mars are not completely separate from each other as they are for the Moon where if you drop some life into a lunar crater - first it's never going to reproduce there - but also - it's just going to stay where it was dropped. Even with the Moon - though there are no requirements yet to keep it clean of life for planetary protection - there could be issues if we want to study, say, traces of ancient organics in the ice in the polar regions. But it's not a big deal for the Moon because there is no atmosphere and apart from a bit of micrometeorite gardening - so long as you document where it is that you leave any organic wastes on the Moon or indeed document the location of any crashes with human occupied spacecraft - well the only part of the Moon that is affected is the crash site - or the waste tip itself.
But on Mars with its global dust storms then a crash on Mars or a waste tip there - potentially affects the entire planet. Would need very thorough study. Especially since the dust storm iron oxide particles are good at protection from UV light, so helping to protect microbial spores that are spread around the planet.
What we could do is to send humans to Mars orbit. I think that's what we should do first. It's lower cost, and safer for humans as well as for the planet.
And I'd advocate a particular way of sending humans there also. I think we should use ballistic transfer. That's a special type of transfer orbit recently discovered where you send the spaceship well ahead of Mars and it gently falls by itself into a very distant orbit around Mars when it gets there, without any need for an insertion burn or any extra propulsion at all.
It doesn't really save on fuel if you want to end up in a low Mars orbit. But it has the great advantage that you don't need an insertion burn. Instead you can gently circle down to lower orbits using much more controllable and gentle methods such as ion thrusters. This means almost no chance of an accidental impact into Mars through misfiring the rocket for the insertion burn - for instance longer than it should be fired for.
That's safer for the humans because it eliminates a possible chance of a crash on Mars, and safer for the planet. Because a crash as a result of a misfired insertion burn could end up with the human occupied spacecraft hitting almost anywhere on Mars, at least almost any longtitude and there are special regions known now even in equatorial regions. But as I said, I think because the planet is globally connected through dust storms and its atmosphere, that until we know a lot more about the planet, no humans should land or crash anywhere on the surface. Because we sadly can't be sterilized of Earth microbes and a human occupied spacecraft carries trillions of microbes in tens of thousands of species, many not yet known to science, the so called "microbial dark matter".
It would be a very exciting mission, like the ISS, orbiting above a planet, but not Earth, orbiting in a close orbit above another planet, Mars. And also controlling rovers on the surface in real time, close up telepresence. We'd learn so much and it would be very fulfilling for the astronauts. They could also visit Phobos and Deimos - after first sending robotic missions there to find out about what those tiny moons are like close up - and with prior experience on the Moon to see how much of an impact a human base has on an airless world, and how best to handle such situations.
So anyway - if you then ask the question about that - an orbital mission rather than a surface mission - I think it's possible but I think it would be likely to be a global undertaking involving just about all space faring nations, like the ISS. Probably more expensive than the ISS at least with present day technology. And not sure that it is possible to do it safely yet.
And I think it would probably involve private commercial companies also. And I think that's for at least a decade or two into the future, but could well be longer. We might find that sending humans as far as Mars, even to orbit, is more of a challenge than expected.
I think we should start off with missions closer to Earth such as the Moon, which has lots to learn about. That itself is a pretty huge challenge. The Apollo missions may have made it seem easy but that was a very risky undertaking, and they only spent a couple of days on the Moon each time, and only just scratched the surface of lunar exploration. And we don't have that capability any more, so first we need to rebuild that capability, and show that we can still send humans to the Moon.
It would be a major challenge to do sustained long term exploration of the Moon from a human base there, if that's what we do. Apollo just made a beginning there. It's like the difference between modern Antarctic bases, and the very first missions to Antarctica by Scott, Amundsen, Shackleton etc.
This shows Amundsen's party looking at the Norwegian flag at the South Pole on 14th December 1911. Roald Amundsen
This, and the other early explorations of Antarctica in the late nineteenth century and early twentieth century were just the start of Antarctic exploration, not the end of it.
In the same way the Apollo missions to the Moon surely are just the start of lunar exploration. And since the Moon is so much closer than Mars I think that in the future we will decide that it is the best place to begin our human explorations of the solar systems.
Robotic spacecraft can go into dormancy, and for them, a voyage of many years is not much different from a voyage of a few days. The main difference is the light speed delay when they communicate back to Earth and a weaker signal because they are so far away.
But humans can't do that, not yet anyway. For us, there's a huge difference between a place we can get to with two days of travel and a place that requires six months of travel to get there.
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