With a human visit to Mars planned for only a few decades away, I wonder what thought has been put into methods for keeping Mars free from contamination by earth organisms during a visit by astronauts?
There is plenty of work placed into decontaminating the existing robot spaceships when they visit Mars, but no-one seems to be looking ahead to how the same problems can be tackled for human explorations, or at least, if they are their work doesn't seem to get widely publicised, I haven't read anything about it, while there is plenty of material about human visits to Mars. So this is an attempt to help encourage discussion of these issues.
I can imagine the difficulties may be formidable. The astronauts would have to sterilise their space-suits whenever they leave the vessel, and would need to do so to standards similar to those used to sterilise the existing space-craft sent to Mars - and they would also have to evacuate the space lock completely to a perfect vacuum, and sterilise it every time they leave their base, as they need to make sure that none of the air in the space lock escapes to the surface. The tiniest leak of air from the space lock, or a suit or the space-ship, one that wouldn't be of any danger to the astronaut, would contaminate the surface with millions of organisms. Everything would also have to be recycled and all waste products removed or sterilised when they leave. This seems to suggest technology of a rather higher order than we have available to use now.
Also, if there were an unfortunate accident either on landing or during surface excursions, this would be likely to contaminate the surface with human remains and body fluids (immediately or eventually). Is there any way this can be prevented with existing techonlogy or even foreseeable future technology?
It really doesn't look as if sending new life forms to the surface of Mars is a very sensible way to search for existing life there! Terrestrial analogies even with Antartica aren't close enough because on Earth many microscopic life forms can easily spread to any continent born on the wind or via the oceans, while if there is any exchange of life forms with Mars at all, this is exceedingly rare.
I'm not trying to say that Mars should never be visited by humans, only to ask whether we are ready to do so yet. Perhaps this century isn't yet the right time, and perhaps it may not be for some long period to come. So very many questions would need to be considered, and probably we just don't know enough to be able to answer some of them yet.
Some think there may be water underground in places in Mars and that underground Mars may be one possible niche where microorganisms may still thrive there. If nothing is found on the surface, how long will it take to search the entire subsurface habitable areas of Mars remotely to check for any traces of lingering microorganisms from its wetter past?
For some thoughts by experts on terra forming mars, see Space Daily - Giving Mars Back its Heartbeat. Great Terraforming Debate: I, II, III, IV, V, VI, VII, VIII
Might introduced life forms mask signs of Mars life? Might they compete with martian lifeforms and drive them to extinction (as has so often happened on earth with the far smaller travel distance from just one continent to another)?
Then there is another question which applies whether or not there is life already on Mars in any form. I've not seen this discussed anywhere, but it seems a point that should be considered. Might introduced life forms evolve into diseases harmful to humans? Mars could turn into a laboratory breeding new life threatening organisms. Many of the seed life forms would be human parasites and symbiots, suddenly given an entire planet to colonise, so that sounds potentially rather dangerous! We have nothing like that on Earth to compare it with.
Or might introduced life forms be used deliberately as a way to terraform Mars. If so, I hope it would be after many years of research - probably more like centuries - to discover any existing life forms there first, and then to consider the effects of introducing the new life forms. If there is some tiny patch of remnant life existing in one tiny subsurface lake, maybe closed off by an ice covering, how long would it take one to find it? There needn't be any signature of its presence in the current atmosphere if we are talking about a remnant population that has just managed to stay on after all its cousins have gone extinct and has only limited contact with the current Mars atmosphere..
There has been a lot of study of ways of terraforming Mars, and as study it is interesting research. There is no need to halt the research - but do we want to actually carry it out right now, even if all the theoretical matters can be resolved.
One consideration is that Mars could easily lose its volatiles. It has a low gravity and a low temperature, but temperatures are not so low as Saturn's moon Titan (which has a thick atmosphere, but exceedingly low temperatures).. It can't hold onto the lighter gases for long. Water may dissasociate in the upper atmosphere of Mars and the hydrogen get lost to space. Unless some counter measure is used, a terraformed Mars with liquid water on its surface will probably lose all its water over geological time scales.
Maybe Mars will be needed by our future descendents, for instance as a temporary abode in the remote future when the Sun enters its red giant phase. By then our descendents may know far more about possible effects of terraforming than we do now. Mars may even become habitable briefly in the natural course of events as the sun becomes hotter. Again just for short times geologically speaking, but it could well be a time when there is no other habitat for life in our solar system, with the Earth made uninhabitable because of its proximity to the brighter and expanded sun. Mars could become the only abode for life at that stage. Perhaps we just need to be patient and wait (over geological time scales).
Maybe the answer is that astronauts will need to explore Mars by tele-presence from Mars orbit. In order to work well via tele-presence in the Mars conditions, they probably need to be living under Mars type gravity and this could be done in pairs of spacecraft tethered to each other with the tethered pair turning slowly about the tether mid-point. Of course that could be done from Earth orbit too - the point in voyaging to Mars would be to remove the time lag, which is possible if you are in low Mars orbit.
We need not be discouraged if the only exploration needs to be via tele-presence and semi-autonomous rovers. With future developments of technology this has potential to be an interesting and exciting way to explore the planet.
Robert Walker