Would you want to live on a "snowball planet", covered with ice sheets and glaciers all the way to the equator? Mars only looks warm because the photos are digitally adjusted to match brighter lighting on Earth, and because it lost most of its water long ago.

It's so cold at the equator (warmest places on Mars) that carbon dioxide could freeze to dry ice at night. On Earth this only happens in the coldest spots in the interior of Antarctica in the middle of winter.

This is just one of many reasons why Mars is less than ideal as a place to live. This is an update of my Ten Reasons not to Live on Mars, Great Place to Explore.

=A photograph of the snow surface at Dome C Station, Antarctica, it is representative of the majority of the continent's surface
Snow surface at Dome C station in the interior of Antarctica. If Mars was covered with ice like this, it would be a far better planet for colonists.
Record low temperatures in Antarctica
Record low temperatures recorded by satellite in the mountains in Antarctica in the middle of winter. This is the only place on Earth that gets as cold as the equatorial Mars nights.

2. Mars has a near vacuum for an atmosphere. After a major breach in your habitat or spacesuit, you die within seconds. You might as well be in space. The air is so thin, that moisture in your mouth and lungs would boil at blood temperature.  

 Charles Conrad Jr., Apollo 12 Commander, examines the unmanned Surveyor III spacecraft during the second extravehicular activity (EVA-2). The Lunar Module (LM) "Intrepid" is in the right backgroun
The Apollo 12 commander Conrad examining the unmanned Surveyor rover on the Moon.

You would die instantly on Mars if your spacesuit or your habitat fails, just as on the Moon. Mars does have a slight atmosphere, but it would count as a vacuum on Earth. The pressure is a tenth of the Armstrong limit, the point at which moisture on your tongue or in your lungs boils at blood temperature.

3. Anyone on the surface would be exposed to cosmic radiation, because the thin atmosphere gives hardly any protection, and Mars doesn't have enough of a magnetosphere to deflect the radiation. The NASA career limit for astronauts is based on a 3% risk of cancer in your lifetime. They also estimated that any astronauts who die of cosmic radiation induced cancer have their life expectancy reduced by 15 years approximately (this depends on your age, and whether you are a man or a woman, and the margins of error are large).

If you follow those guidelines, adults over 30 could spend an average of two hours a day in spacesuits, if they are willing to take a 3% chance of a fifteen year life expectancy reduction. This would include time spent in vehicles roving over the surface as these can't be shielded with meters thick layers of regolith.. It would also include time spent in greenhouses on the surface if illuminated with natural light - because the amount of air in a greenhouse wouldn't give any protection from cosmic radiation. Basically humans would need to be pretty much troglodytes, living under several meters of soil for most of their life, on Mars.

That is unless you deflect the sunlight into the greenhouses with giant mirrors - that's how they get around the issue with the space habitats such as the Stanford Torus - mirrors that reflect light in an angled path around into the habitat, but cosmic radiation just flies straight through the mirrors and is blocked by the shielding, so can't get around the angles into the habitat.

Cosmic radiation damage, credit NASA
This shows cosmic radiation damage of DNA. On the surface of Mars every cell will get hit many times by highly energetic cosmic rays, which on Earth are absorbed by our thick atmosphere and the magnetosphere. Mars has no thick atmosphere and almost no magnetic field.
Most colonists would spend as much time indoors as possible. If you limit yourself to a couple of hours out of doors (including in vehicles) a day, that leaves you with a 3% extra risk of a cancer, as best as we can estimate it at present. Of those who die from cancer, on average their life expectancy will be reduced by 15 years (these figures have large error margins).

Fetus's are especially vulnerable to radiation, based on data from Hiroshima (it's a different type of radiation but the best data we have) then effects could include for instance, severe mental retardation, so it wouldn't be safe for pregnant women to go outside a shielded habitat at all. Babies and young children would also be especially vulnerable.

Most colonists would surely spend nearly all their time inside the habitats for safety reasons. You would only go out if you had to.

4. It's not known if you can stay healthy at Martian levels of gravity a third of Earth's. The only evidence we have is for zero g, and that's not encouraging.

Astronauts in orbit in the ISS suffer from many issues including, bone loss, eye problems, thinner blood, more blood in the upper body, increased resting heart rate, greatly increased levels of adrenaline, reduced digestion, liver and kidney function, reduced thirst leading to dehydration, increased core temperatures, can only get rid of heat by sweating, not by convection so increased sweating leading to magnesium deficiency, can't take most medicines orally, only subcutaneously because of the stomach, liver and kidney issues, the list goes on and on.  It's not known if humans can live long term in zero g. The record is 437 days but the Russian cosmonaut who survived that long in space might just be extremely lucky.

In a recent space show a doctor William Rowe, a specialist in human physiology in space. gave as his opinion that because of all these complications, most people would die within two years of exposure to zero g. It's also likely to be unsafe to carry a fetus or give birth in zero g, though it is unethical to do the experiment to find out for sure. Pregnant women are not permitted to fly to the ISS for this reason. 

Bunny hopping on the Moon

It looks fun but nobody knows if humans can stand low gravity for long periods of time. Zero g is definitely bad for your health with many serious complications and humans probably can't live in zero g indefinitely. Zero g is also probably unsafe for a developing fetus or pregnant woman, but it is unethical to try the experiment so no pregnant woman is permitted to fly to the ISS.

Nobody knows if low g is safe, or has similar problems as zero g. The experiments haven't been done yet in space, and you can only simulate low g on the surface of Earth for a few seconds at a time.

Mars gravity may be fine, but nobody knows at present. If you need full g for health, you might need artificial g on Mars, with carousel type spinning habitats, as in space.

5.This is more of a minor point, but is one of the reasons that make Mars far more inhospitable than the Earth. Most of the equatorial regions have no ice at all, probably to depths of kilometers.

It does have ice mixed in the soil at higher latitudes, as well as ice patches and polar ice caps, and may have a few places with trapped subsurface ice in equatorial regions also. You could extract this as water. One recent suggestion for a way to do it is to microwave the soil.

Ice is reasonably common in the solar system. Mars' moons probably have ice in them for an orbital colony.

Other resources are also hard to extract, especially compared with Earth. Its atmosphere does have carbon dioxide gas for instance, but it is a near vacuum, so you have to pump the air out of a near vacuum to use it. It has no free oxygen (has to be split from water, mechanically or using algae and plants), and nitrogen is scarce, needed for plants and as a buffer gas to breath.

6. You are totally dependent on technology, with a long supply chain from Earth. If you get any damage to your spacesuit or habitat, or heating system, or life support, you have to repair it with whatever you have on the spot. If you haven't got what you need to repair it, you have a wait of over two years, in worst case, for supplies from Earth. The fastest they can get to you is about six months if you are really lucky. 

If you can't repair your spacesuit, you may be stuck inside your habitat for two years. If you can't repair your oxygen generators, air scrubbers, machines for melting ice to water, heating, or any other component of your habitat's immensely complex life support system, you die.

If some Apollo 13 type emergency arises, then you are much more on your own than the Apollo astronauts. Any conversations you have with Earth during the emergency will have delays of up to 40 minutes between anything you say, and the response from Earth. Try to imagine how the Apollo 13 disaster might have unfolded, if the astronauts had to wait 40 minutes for a reply from earth with each conversational interchange.

Apollo 13: Houston, We've Got a Problem (1968 film about the crisis)

If you have a crisis like this on Mars, (including Mars orbit) then there will be no easy dialog back and forth. It will take 40 minutes to get a reply from Earth to anything you say. And if you need new components from Earth, it can take over two years to get them to you.

7. There is no oxygen in the air and you can't terraform Mars  to make it like Earth in any reasonable timeframe. The most optimistic projection by Robert Zubrin, a Mars colonization enthusiast and founder of the Mars Society is 900 years. This assumes use of giant mirrors in space and such like advanced technologies.

This looks like it might be easy, but what you may not realize is that the most optimistic estimates make it 900 years, with the aid of giant mirrors in orbit around Mars and such like technology. Most think it would take tens of thousands of years to get a breathable atmosphere like Earth. And along the way there are many ways it can go wrong, and put Mars into a state where it might be hard to recover, for instance, situations with atmospheres poisonous to humans, or back into the current state but without some of the water and dry ice Mars now has (the failed attempt could lead to it getting bound up as rock).

You would also seed Mars with a mixed bag of microbes at an early stage, which might well get in the way of future attempts to terraform the planet.

In short, Mars won't be at all Earth like for at least several centuries, and possibly never.

Most experts on the subject come up with figures of 40,000 to 100,000 years to get an oxygen atmosphere like Earth, though an atmosphere suitable for plants only may be possible within a few centuries or millennia. That's assuming that everything works perfectly, and there are many things that could go wrong. For more see To Terraform Mars with Present Technology - Far into Realms of Magical Thinking - Opinion Piece and Trouble With Terraforming Mars.

8. .Humans are not needed on the surface of Mars for exploration. The most detailed study so far shows that a single mission to orbit with telerobotic avatars could achieve as much as three missions to the surface. (This is the paper and here is a powerpoint presentation which is worth reading as it goes into a detailed point for point comparison with a surface mission. )

This is an area that needs more research, and hasn't been studied in a huge amount of detail, but the research so far certainly favours a telerobotic mission over a surface mission. If this is true, similar considerations would also apply to the Moon and other destinations that require use of spacesuits on the ground.

The problem is that you are so clumsy inside a spacesuit, because of the near vacuum outside it, and the pressure difference between the inside and outside. It's like working with your fingers inside a pressure hose, stiff and tiring. For instance the Hubble repair mission could probably have been done with telerobots. Indeed, there was a plan to repair Hubble with telerobots at one point. 

This is an area of ongoing research, with a major Exploration Telerobotics Symposium in 2012 at the NASA Goddard Space Flight Center, and with experiments last year to control a rover on Earth remotely from the ISS, and development of telerobots in space to repair satellites by remote operation from Earth. (Some of this research is by the researchers at Goddard space centre who developed the tools for the Hubble repair astronauts to use).

This is a recent telerobotics test, simulating an astronaut in orbit controlling a robot on a planetary surface.

First, controlled by an operator in a separate control room on the Earth.

Then the next picture shows an astronaut in the ISS controlling the same robot on the Earth.
Controlling rover on surface of Earth.

In another recent test, researchers at the Goddard space centre on the ground successfully cut a thin wire on a mockup of a satellite on the exterior of the ISS, and removed fuel inlet covers, a complex procedure in space - and then successfully simulated refueling a satellite in orbit.

Here you can see it cut the wire at 1.51 mins (it may seem slow but then astronauts are also slow) - it is not totally teleoperated actually. Rather it follows pre-programmed instructions but the operators on Earth correct for small discrepancies in real time, to keep it on track, e.g. if it is not positioned quite right to cut the wire, they can change its position.

Dextre makes the cut

It is early days yet, but it seems likely that telerobotics will be used more and more for servicing satellites in Earth orbit and for explorations e.g. of the Moon. On the Earth, telerobotics are used for deep sea drilling, exploring ship wrecks, for work in radioactive surroundings, and doctors use them for remote surgery also, in a landmark case ten years ago a surgeon in the US operated on a patient in France via telerobotics. 

In the simulated rover mission, astronauts on the ISS could drive it at up to 1 mph just using keyboard methods. That's already far faster than our rovers on Mars such as Curiosity, which can only manage 100 meters a day at maximum speed. Curiosity drove a total distance of 1.6 km (just under a mile) in its first year on Mars.

The ESA is also actively exploring these ideas. Here is a prototype for an exoskeleton arm from their ambitious Metotron project.

Prototype of the exoskeleton arm the European Space Agency is building to control robots from space. ESA

This video gives an idea of how it works: Controlling Robonaut R2A in ROS with Exoskeleton

More ESA telerobotics lab videos

Lockheed Martin have proposed a mission to explore the far side of the Moon. You could position a space station at the L2 point, where astronauts could control various robots on the lunar far side - as a useful precursor to similar missions further afield such as to Mars. 

Lockheed Martin proposed mission to explore the far side of the Moon by telepresence with astronauts at the L2 position which is situated just beyond the Moon on the line joining Earth to the Moon, which is relatively stable (not an equilibrium position but space craft can stay in its vicinity easily with occasional adjustments)

Drilling on Mars does not require humans either, as is often said. Humans in spacesuits are clumsy at drilling also. It can be done with technology such as remote controlled "moles". These could drill to depths of kilometers and seem to be the best solutions in the unusual dry, near vacuum, and cold conditions of the Mars sub surface.

9. If the main motivation of the space mission is to land humans on Mars, then as soon as that is achieved, people on Earth are likely to lose all interest in future missions by humans to Mars. You might find that hard to believe, but I lived through the Apollo landings in the 1970s. 

The interest in the Apollo missions in the build up to Apollo 11 was far higher then than the interest in a Mars landing now. Yet within a surprisingly short time, a year or so later,  the public lost almost all interest in the activities of the astronauts on the Moon, and the program was soon cancelled. We have not been back since then. 

On this day, NYT
The Apollo 11 landing in 1969 was a huge news story, and filled the newspapers. As a child I made a scrap book which I filled with all the stories I could find about Apollo 11 and the other space missions at the time. There was great excitement and interest. It is hard to realize how much now, people looked up at the Moon and it was a matter of wonder to many, to think that there were humans walking up there. But by 1972, the world and politicians had lost interest.
Harrison Schmidt on the moon
In 1972, Harrison Schmidt was the first scientist to land on the Moon, a geologist (who trained the other astronauts in their geological field studies), who found he had all too little time for all the things he wanted to do on the surface, and who found a rock dubbed "the most interesting rock returned from the Moon". The public though had lost interest by now, politicians axed the program, just as it began to reach the point where it was possible to send scientists to the Moon. A similar thing could happen to a human mission to Mars.

Many of the "Mars One" colonization enthusiasts are not interested in going back to the Moon because "it has already been done". If that's your motivation, then as soon as colonists land on Mars, it will "be done" and just like the Moon is now, will be of no more interest to others like you in the future.

10. Every two years you get dust storms. Sometimes these last for weeks on end, even months, and may block out 99% of the sunlight. Here is a photo showing progression of a dust storm as seen by Opportunity.

Progression of Mars dust storm over three days, Opportunity Rover

11. There is dust everywhere, and (in a recent discovery in 2013) this dust has levels of perchlorates that would be toxic to humans (though some microbes like it fine and could use perchlorates as food).

12. Humans on Mars will greatly increase the risk of contaminating the planet with Earth microbes. It is so sad if they do. Of all the places in the solar system, Mars, and Europa are the two places currently thought to be of most interest for study of life and evolution. They are the two places we should keep free of Earth life at all costs, at least until we get a chance to study them.

If we introduce Earth microbes to Mars, it might well be like introducing black rats to Galapagos. Galapagos islands do have shared ancestry with other Earth life, same DNA and so on, and indeed birds can fly to the islands also. But they've never had black rats, and they are devastating the wildlife there which is used to ground nesting, for instance, without predators.

There may well be microbes on Mars, present day life, and if so, then it is unlikely that there has been much contact between the Mars and Earth for many millions of years, and quite possibly for billions of years, and nobody knows for sure if any life has been transferred between the planets.

There may be a few microbes that could make the transition after the largest meteorite impacts on Mars or on Earth, but not many could do it and it is possible that none ever made the transition. Though Earth life is not adapted to Mars especially, yet, it might be able to out compete native life because of some adaptation the Mars life has never encountered.

Mars especially is a near twin of Earth in the early solar system. It could give us priceless information about evolution. 

The simplest cell we know, and probably the simplest cell possible with modern machinery of life is 200 nm across. It is far too large and complex to arise by chance in one go. Indeed if you measure the way the complexity of DNA has evolved, then we have only half the story of the evolution of life. 

What we know about evolution is like a 20 chapter book with the first ten chapters ripped out. All we have on Earth of those ten chapters are some sub millimeter scale zircons, preserved in younger rocks in Australia. These can tell us a bit about the isotopic composition of the atmosphere of early Earth. That is about the only direct information we have about conditions on Earth during the entire period of evolution of DNA and the modern cell.

Study of early Mars in its pristine state can help us fill in those missing chapters. It is possible that Earth life actually originated on Mars. Or it could have seeded Mars. Or life evolved independently on Mars. Or indeed all three of those could have happened. Either way, we can learn a lot about evolution or about exobiology.


Well if you really really want to go to Mars no matter what;  if you've caught the Mars bug bad, then the first eleven reasons can all be addressed in one way or another. You would expect it to cost a lot more,  maybe an order of a magnitude more than a mission to Mars orbit, and with greater year on year expenses also to keep it going. Probably it is also more dangerous for the astronauts especially for the landing on Mars. You also have the additional risks of accidents during EVAs on the surface, which you don't have for a telerobotic mission (only the telerobot gets damaged). Then of course you also have the additional risk that you can't return from a Mars direct or Mars one type surface mission at all, while it is easy to return from an orbital mission.

But if you don't care about extra expense, and additional risks, and want to go to the surface at all costs, there are things you can do to deal with all the other eleven reasons.

You can build a habitat on Mars which is like a space habitat, on a planetary surface. You can cover it in regolith, to several meters of thickness, and go outside it rarely.

If low g is poor for your health, then you can have carousel type artificial habitats to increase the gravity. Though you can't terraform Mars in a reasonable timescale, you can paraterraform it, cover it with greenhouses. If you put enough money into the problem, maybe you could get to the point where the Mars colonists can build factories on Mars, in the vacuum conditions there, to make their own electronics and machines.

So all that could be solved if you really wanted to and were willing to pay enough to solve them. But no matter how wealthy you are and how much financial support you can get, number 12 is the biggy which you can't do anything about.


Galapagos has its programs to eliminate the black rat. But what can you do if you contaminate another planet like Mars with Earth microbes?

As far as I can see, there is no way, at present, to send humans to Mars without greatly increasing the risk of contaminating it with Earth life. Apart from any other consideration, the planetary protection scientists would need to look carefully at the effects of a hard landing by a human party. That would be an immediate and huge risk of contaminating the planet. And once a new species of microbe has been introduced to a planet, and started to reproduce widely there, we know of no way to turn back the clock to a biologically pristine Mars.

So, the last one is different. If you make a mistake with Mars, by introducing undesirable microbes to the planet, then, as far as I can see, no amount of money can fix it. 


If you want to colonize the Moon, Mercury, Venusian clouds, build space colonies from materials in the asteroids, or orbiting colonies around Mars, well I'd say, go for it - so long as you take reasonable care to make sure here is no life there before you build your colony, and take care to make sure you don't destroy things of great scientific interest.

This is a bit like the way developers work, that you let the archaeologists examine the site first before you begin construction. If it's done like that, I see no problems with anyone who wants to colonize these places. 

Venus may have life in its upper cloud decks. The ice at the poles of the Moon is far too cold for life, as we know it, but may have interesting records of the past solar system which needs to be studied first. Even Mercury just possibly could have life in its polar ice caps. So there may be other places where we need to proceed slowly also, and some of these may also be of extraordinary interest. We won't know until the scientists get their chances to explore them properly.

So, you shouldn't count on colonizing them either, until they are studied first and you get the green light. That's similar to the situation for archaeology again.

But Mars is of such great interest for biology, and it is hard to see how it could be colonized in a biologically reversible way. So, it is hard to see it opened for colonization in the very near future.

Mars, Europa and Earth to scale
Mars, Europa and Earth to scale. As far as we know, These  are the three places in our solar system most likely to have both present day life, and evidence of evolution of life.

Mars is of special interest because it had oceans, then rivers and lakes which were also probably habitable as best we can tell, in the early solar system, and has signs of present day habitability as well, especially the recently discovered equatorial warm seasonal flows.

Europa is especially interesting because it has a subsurface ocean, almost certainly and this is probably oxygen rich as a result of the ionizing effect of Jupiter's radiation on the ice above it.

This makes Europa and Mars the two places in our solar system of especial interest for the search for life. This also makes them the two places that are most vulnerable to contamination by Earth life.

The difference with Mars really is that the "archaeologists" - in this case the exobiologists, have an entire world to examine, not just a few square meters of builder's site. What's more, it's a world that has many different and varying terrains, including the deltas, ancient ocean margins, geysers, dry gulleys, warm seasonal flows, polar ice caps, subsurface deliquescing salts, ancient river beds, caves, with a total surface area the same as the land area of Earth... It probably has many sub surface habitats you can only examine by digging, and traces of ancient Mars likely to require digging ten meters below the surface to find pristine samples. It's going to take them some time to assess it. And I think myself that there is a high chance that, given time to find it, they will find much of biological interest there.


I'm no lawyer, but speaking as a lay person, it seems that basically we have a conflict of freedoms here. There is the freedom to colonize, and there's the freedom to enjoy Mars in its biologically pristine state and to benefit from the discoveries that would come from study of a pristine Mars.

If a human expedition lands on Mars at present state of knowledge of the planet then those two freedoms conflict. The Outer Space Treaty clause is about "harmful contamination" and this has been interpreted as meaning, preventing contamination that harms the scientific experiments of other nations.
So, in this case, if the human mission contaminates Mars in a way that is harmful to scientific experiments by other parties, the OST supports those who want to keep it free of contamination.

I suggest we should postpone colonization of Mars until we know what the effects of our actions will be, and be prepared for the possiblity that it might not be a suitable place to colonize in the near future. Instead we should proceed in an open ended mission of discovery and exploration, and leave the big decisions about whether to colonize Mars, terraform it, paraterraform it, return it to conditions resembling the early solar system, or whatever, to the future, when we know more about the planet.


This is based on my "Ten Reasons NOT To Live On Mars - Great Place To Explore", (and "Ten Reasons Not To Live On Mars, Great Place To Explore" - On The Space Show) - with some new material, and exploring a different way of organizing and presenting it.


Zubrin and others have given some counter arguments, which they believe show that it doesn't matter if we contaminate Mars with Earth life. So let's look at these.

1. Mars has exchanged life with Earth already. So if there is life there already it is no different from the life we would bring to the planet.

Answer: Yes is true that there are meteorites that impact on Mars and Earth and these sometimes send debris from one planet to the other. But this happens rarely. Yes we get many tons of material from Mars every year, estimated. But those come from just one or two impacts on Mars, the most recent 700,000 years ago. That's so long ago that any meteorites from Mars we receive now, unless it's many meters in diameter,has been thoroughly sterilized by cosmic radiation during the journey here. Also many of the habitats suggested on Mars are fragile and close to the surface such as the warm seasonal flows, or deliquescing salts - or deep underground. Also the surface habitats are probably only sparsely populated, and only found in particular regions of Mars. The chance that an impact on Mars will hit such a habitat and that it will survive the journey to Earth unscathed must be low. And only a tiny percentage of Earth microbes could survive the journey anyway' if there is life on Mars, the same may be true for it.

From Earth to Mars, then you need much larger impacts to eject the material out of our thick atmosphere and higher gravitational field, such as the one that ended the Dinosaur era. That one is unlikely to have sent viable life to Mars as it landed in the middle of a tropical sulfur rich sea, not the most likely place to find cold tolerant and ultra violet tolerant extremophiles also able to survive cosmic radiation in a journey through space.

And the bottom line is that we have no direct evidence of life transferred from one planet to another by meteorite. Experts think there is quite a good chance it did happen in the early solar system, when there were many more meteorite impacts than there are now, but that also is simply a hypothesis that will only be confirmed if we do find life on Mars that is genetically related to Earth life.

If it is true that life was exchanged between the planets in the early solar system, then either Earth life seeded the early Martian oceans in its Noachian period or Mars seeded Earth, or both.  But this might not have happened, and it also remains possible, on the data so far, that there is no life on Mars, or that there is life, but not related to Earth life. That last is the most interesting of all.

Mars could also have a mixture of some life related to Earth life and other life forms that are unrelated.

For more about this argument, see: Could Microbes Transferred On Spacecraft Harm Mars Or Earth - Zubrin's Argument Revisted

2. We have contaminated Mars already with Earth life with our spacecraft, so why bother protecting it any more?

Answer: This may be true but most think it is unlikely. It is true that there have been breaches of planetary protection such as the impact on Mars surface of the Mars Climate Observer spacecraft only sterilized for orbit, and the early Russian missions which were probably not so well sterilized - and arguably also Phoenx lander since the evidence it found suggested a possibility that its landing site might have sub soil habitats for life and it wasn't sterilized to the levels needed for such a site. Yes it is true that these could have contaminated Mars, but there is good reason for optimism here.

The surface of Mars is extremely hostile to life, except in a few areas such as the warm seasonal flows, and possible places where the sub surface mixtures of chlorides and sulfates are just right to get deliquescing salts at the right temperature and water activity ranges for life to survive. For the life to survive, you need the right kind of extremophile to hitch a ride on the spacecraft and then to be delivered to the right habitat on Mars for it to survive in.

Until we can send a spacecraft to Mars to examine the crash sites and lander sites for evidence of contamination by Earth life, we won't know for certain. But on the evidence so far, it seems reasonably likely that we haven't yet contaminated Mars irreversibly.

For sure, there is dormant life on the spacecraft on Mars. But this is reversible contamination. If it's necessary, then we can go back to Mars and remove all the spacecraft or decontaminate them, and the areas around them, and return Mars to its pristine state free of Earth life.

So it's true, we have sent microbes to Mars which have viable dormant life on them, almost certainly. But this contamination is probably reversible.  

If it turns out that we have contaminated Mars, then that is all the more reason to take care not to introduce new life to Mars. If you accidentally introduce black rats to an island with interesting species, and they eat the eggs and devastate the wildlife, then that is all the more reason not to introduce feral cats and dogs to that island, or cane toads. Instead, your next step would be to see if there is anything you can do about the rats, and do what you can to minimize their impact.

3. That it doesn't matter if we introduce life to Mars because it will be easy to distinguish it from native life through looking at its DNA sequence and adaptations.

Answer: First, many species on Earth have surprising adaptations and just because it is in a human habitat doesn't mean it is not adapted for Mars. For instance extremophiles have been isolated from human belly buttons and from the tongue. That's because lifeforms tend to retain their adaptations for extreme conditions.

Then, we don't have a database of all DNA on Earth. Hardly any microbes have been DNA sequenced. Indeed less than a third of the 100 main families of microbes have any described species at all, never mind fully DNA sequenced species. That's the problem of microbial dark matter.

Then again, microbes are so little understood that some scientists have hypothesized thatt there is a shadow biosphere of non DNA based life. Another hypothesis is that nanobes are alive. These are tiny structures smaller than the smallest known cells, which look like micro-organisms under an electron microscope.

Certainly nanobe sized microbes must have existed in the past before the evoluion of the more complex and larger ones we have today. Some scientists have postulated that the present day nanobes are alive, and are just not recognized as life because they are so small and hard to study. You can only see these structures clearly in the vacuum conditions of an electron microscope, when they are of course dead. Others say these are not forms of life but form inorganically. The question has not yet been settled conclusively either way.

So, we might find a form of life on Mars and then only later recognize it as a form of life we also have on Earth. This is a more remote possibility but can't be ruled out; that a human landing party could contaminate Mars with lifeforms that we don't yet recognize as life.

You can recognize well studied and sequences microbes easily, as in Robert Zubrin's example of anthrax. You could tell if it came from Earth, perhaps, if you could DNA sequence every microbe in the habitat before it lands on Mars. But that is impossible. Only 1% of microbial species in any habitat typically can be cultivated. A human habitat landing on Mars would be home to thousands of undescribed, unsequenced microbes not yet known to science. There is no practical way to DNA sequence them all before a landing. Any attempt to sample the species diversity would be bound to leave many of them out.

Then the threat is not just the confusion with Earth life, as Earth life could also make Martian microbes extinct. It's possible that Earth life with its longer and more complex history of evolution has evolved mechanisms that the Martian life has not yet found. If so, after a period of rapid evolution, radiation and adaptation, Earth life could render Martian life extinct.

Then, most of the proposed instruments don't look for life directly. Instead they look for amino acids, fragments of DNA, or a chirality signature; robust signatures of biological activity. These instruments are now so sensitive that they would be confused by a single amino acid or a single DNA fragment or protein fragment in the sample.

So a human landing on Mars would also contaminate the area around the habitat with amino acids, DNA, proteins and so on. This would totally confuse any searches with the senstiive instruments we want to send there. So for instance after a human mission to Gale crater, you would probably treat any detection of an amino acid in the crater as likely to be from the human mission.

Any amino acids from ancient Mars, near the surface would be reduced several thousand fold in quantities over billions of years, by the effects of cosmic radiation. Also it is clear that life was never very abundant on Mars in the first place, not enough to lay down rich thick deposits of organics as on Earth - because we would find those by now. So you need this exquisite sensitivity for the searches for life, especially for past life.

4. Mars is our only chance of a "lifeboat" to survive destruction of Earth. So we must colonize it, and as quickly as possible, before the Earth is destroyed. Compared with this threat, then the knowledge we could gain from studying a pristine Mars is of no significance as it will only benefit humanity in the longer term.

Answer: If you want to increase human chances of survival of adverse events on Earth then the best thing you can do is to help sort out problems here. Earth is by far the best "lifeboat" in our solar system and would remain so even after centuries of attempts to terraform Mars, building Stanford toruses in space, and immediately after an asteroid impact.

For the foreseeable future, it will be easier and cheaper to build seawater greenhouses and other type habitats on Earth than a totally self enclosed sustaining habitat in space or on Mars.

If you want a habitat that will survive the worst human induced apocalypse again the best place in the solar system to build it is here, on Earth, e.g. in a remote place or deep underground or under the sea. Even after a nuclear winter, the air on Earth would be breathable (if filtered first) and Earth would be far more habitable than anywhere else in the solar system. It is hard to think of a scenario where nobody on Earth would survive, and if there was no support from Earth, then a Mars or lunar habitat wouldn't last long with present day technology.

As for warfare, in an all out war, then a space habitat is more vulnerable than any place on Earth. A single missile, one with no explosives, just through momentum, would breach the exterior and destroy it. If there is a risk of all out war on Earth, then what about the risk of war between Earth and Mars due to some disagreement about space policy or some such? Or a missile sent to Mars because the colony is of a different ideology and perceived as "the enemy"? A Mars colony wouldn't survive in such a situation.

We are protected from such scenarios by the outer space treaty, which prohibits positioning of weapons of mass destruction in space and helps ensure peaceful use of space. All the space faring nations and most other nations have signed it, with the exception of N. Korea. Our only chance of survival in space is to continue to explore space peacefully. Warfare between space colonies, such as we have on Earth, with missiles, is simply impossible with present day technology, as it would destroy all the habitats in a short space of time.

This is the same treaty that protects other celestial bodies from harmful contamination such as by Earth microbes.


The answer is simple, that humans do have a role to play to explore Mars, and can massively speed up exploration compared with robots controlled from Earth. But we need to study Mars from orbit using telerobotic avatars, rather than from the surface.

In a telerobotic exploration, humans live in orbit around Mars, in shielded habitats. They control robots on the surface via telepresence and using virtual reality goggles to see the surface of Mars in real time as they explore it. They also use robotic hands with haptic feedback to pick up samples and examine them, and can control gliders and flying machines on the surface also, in real time. With telerobotics a single crew member could drive the entire distance for the Curiosity mission to date, probably in about a day, depending how fast it can drive. With three crew members, each controlling several avatars deployed to interesting locations on Mars, then you could do enormous amounts of exploration. Do in days, the equivalent of years of exploration from Earth, and in years, do the equivalent of centuries of exploration.

This is much more interesting for the explorers also. It is something we can do sooner, for less cost. Also, it seems from the studies so far that we would learn more about the planet for the same price, and in a shorter period of time than fpr any other mission to Mars. It is the most cost effective way to explore Mars, almost certainly.

Robert Zubrin has also suggested telerobotics, because of the low cost, as a first step towards a human mission to the surface.

However for various reasons, we are not yet ready to go as far from Earth as Mars orbit in my view. 


This is the title of the Lockheed Martin studies. They recommended a step by step approach. First, to send telerobotic expeditions to the far side of the Moon, operating rovers on the surface from a base station at the L2 position behind the Moon. This would have unique challenges an no rover or human surface mission has yet been sent to the far side of the Moon.

It's also a great place to work on telerobotics. The far side of the Moon is the most radio quiet place near to Earth because it is shielded from all radio transmissions from Earth by the thickness of the Moon itself. So one thing you could do there is to build radio telescopes.

This is an artist's impression of a telerobotic rover unrolling one leg of a radio antenna on the surface of Mars. (Joseph Lazio/JPL/Caltech)

Annother useful stepping stone would be to explore the craters of eternal night at the poles of the Moon by telepresence.

Then later missions would be sent to the Mars moons. They recommend Deimos as a first stop there (see their comparision study of Deimos and Phobos)

  • It is close enough to Mars for close to real time telepresence,
  • Has one side constantly facing Mars
  • Is in an almost stationary orbit over the surface of Mars. Any point on the surface of Mars would be within range of a party on the near side of Deimos for hours every day.
  • Has polar craters which are amongst the coldest places in the inner solar system, like some of the Moon's polar craters. This makes them a place to put things that need to be kept cool such as liquid hydrogen, and they are probably a good place to study (just as for the Moon's craters of eternal night), and also may be a source of ice for colonists.
  • Is in direct contact with Earth all day, no need for a relay station.
  • Surface materials can be used for resource utilization and to cover the habitat to protect from cosmic radiation.
  • It's an intersting place to study in its own right.

Another possibility is Phobos. Though each target is in range for a shorter period of time it does have some advantages over Deimos

  • The time delay is less
  • It has a crater, Stickney crater, on the Mars facing side. A party in Stickney crater would be protected from about 90% of cosmic radiation, possibly more, already by the crater walls, Phobos, and Mars itself.

Phobos also probably has a high percentage of material from Mars in its regolith.

Disadvantages of Deimos and Phobos is that it is probably harder to generate artificial gravity in a habitat on the Moons. But perhaps this can be done with either a carousel type approach or with centrifugal sleeping quarters for the crew.

The HERRO mission suggested a near sun synchronous Molniya orbit, which is elongated, similar to a Mars capture orbit. This is the easiest to get to in terms of delta v, needing a similar amount of rocket fuel to a mission to the Moon for the same payload. This has the advantages that

  • Less fuel to get there
  • Approaches the sunny side of Mars twice a day,each time visiting the opposite hemisphere,so the entire surface of Mars is available for telepresence control every day

Robert Zubrin suggested a double flyby mission called Athena. The first flyby takes the spacecraft into an orbit resembling that of Mars itself. It then shadows Mars for half its orbit, so one Earth year. A second fly by takes it back to Earth 700 days after the launch. Advantages of this are

  • Least delta v of all the proposals, so also the cheapest
  • Astronauts are close enough to Mars for direct telerpresence control for several hours for each fly by, still remain close for days after the first flyby and before the second fly by, and close enough to be a major asset over Earth based control for the entire year.

Robert Zubrin's plan has several advantages over Denis Tito's Inspiration Mars, that you can do it more often, roughly every two years,, and it doesn't have the high speed return of Inspiration Mars so less issues with aerobraking into the Earth atmosphere on return, and you have far more time for near to Mars telerobotics. But is a longer mission by 200 days.

Both of these have the disadvantage that you have to take all your shielding for the entire mission with you.

With HERRO, later missions could mine Deimos for materials. If there is ice in Deimos; you could use this as rocket fuel to export this extra shielding to the habitat,

Also with of HERRO, and indeed for the other missions also, you could send supplies to Mars in advance in separate duplicate spaceships before the human mission gets there. Most of the cost of an innovative mission is in the design, so it often adds little to the costs, percentage wise, to make several duplicates of the spaceship.

So, you have a habitat there already, in orbit around Mars,and with all the systems functioning including life support. Preferably, have two such ships filled with extra supplies, before you send the first humans there.

They would be fully fueled lifeboat ships able to get the crew back to Earth, or for them to survive in if systems in the main ship fail. You can also ouse them as extra living space during the mission at Mars, and long term assets in Mars orbit. They could be filled with extra supplies, fuel and spare parts instead of crew and provisions for the journey out. These supplies could be used as extra shielding for the main ship for the stay at Mars. In the worst case you can also canabalize the other ships themselves, for repairs, or transfer the mission to another ship.


Though there are many ideas like these about how to explore Mars, I think it's important to realise quite how little we know about interplanetary travel at present.

In particular, we have no experience at all of low g in space or of artificial gravity. This is a reasonably simple experiment, surely it would cost far less than a telerobotic mission to Mars or the Moon. Send two spaceships to orbit, which could be, two of the supply ships for the ISS. After supplying the ISS, astronatus get into the ships, tether them together and set them to spin around the mid point of the tether to generate artificial gravity. This is an experiment that was done before, but only once, in the Gemini program. They had to break it off after half an hour for technical reasons, and the spin was so slow tha tthe experiment only generated micro gravity which the astronauts couldn't feel.

This would test

  • How short can the tether be for humans to tolerate artificial gravity
  • Can humans adjust to the coriolis effects of fast spinning short tethers (much in the way that ice skaters learn to tolerate fast spins, and sailors to tolerate the motion of a ship at sea)
  • Are there any physiological effects of the Coriolis effects on a human long term
  • What are the physiological effects of low g, such as Lunar or Martian gravity? Are they as bad as zeo g, or as healthy as full g, or something between the two?

We can also send a centrifuge sleeping habitat to the ISS at a later stage. This could test to see if short term exposure to low g or full g, while asleep is enough to counteract the effects of zero g.

We also need to get experience of missions in closed system type habitats. The ISS is so far from a closed system, the astronauts can't wash their own clothes but need to get clean clothes sent to them from Earth and it relies on continuous supplies from earth of food, oxygen water and so on.

The Russians did pioneering work on Earth using algae to generate all the oxygen needed in a crewed habitat on Earth. But this is just one aspect of a system We have no experience at all of closed system habitats in space. This is complex technology and needs to be tested close to Earth first before we send closed system habitats to other places in the solar system.

Either that, or we send all the supplies for the entire mission,, as an open system as for the ISS. That's not as bad as it seems as the total weight of supplies is small compared with the weight of the fuel for the return to Earth.


I think there are many potential benefits from human exploration of space. But this is going to work best if humans and robots work together, each doing what they do best. 

  •  Humans are good at decision making, innovative solutions, and driving around and piloting through unknown terrain in real time.
  • Robots are cheaper to send, need no life support, can be sent to places that are dangerous to human life, and can be sterilized so that they do not contaminate the place or planet.

Telerobotics gives us a way to combine the best features of both. 

For an overview, there's a good article about telerobotic exploration on wired.com Almost Being There: Why the Future of Space Exploration Is Not What You Think

So now let's go back to the telerobotics and take a look at how the avatars on Mars can be operated. Here is an artist's impression created for the 2012 Telerobotics Symposium again:

You see the astronauts operating telerobots on the surface in a conventional way, operating them from a desk. 

Some of the telerobots on the surface may have human like hands with haptic feedback so you can pick things up and feel them. The telerobots can also be equipped with stereo vision, and the astronauts could have virtual reality style goggles, so that they can see the surface in 3D in real time as for a computer game.

However, as time goes on, the astronauts could have a much more immersive experience than that.

Here is how it works with some computer games:

Omni in Skyrim - with Kinect 2

The virtuix omni - a low cost omni-directional treadmill used for immersive experience by gamers.

It is light, just a few kg, easily light enough for a space mission. Perhaps this might be a good way to control avatars on the surface.

As in the video, then the player in the treadmill controls the speed by walking, there is no need to map your feet directly to the avatars feet. The avatar doesn't have to have legs actually.
Your Martian avatars would probably have wheels rather than legs, at least to start with - or they might have whegs.

Whegs 2, a wheel leg robot - this type of robot locomotion could be useful as a way to explore the Mars surface (the HERRO mission plan used whegs).

It could also use entomopters. This is a method of flight inspired by bumble bees, which doesn't work in the same way for such large robots on Earth but can be used on Mars because of its thin atmosphere.
Entomopter based aerial Mars Surveyor mission

You could also pilot gliders, and small planes, as in early NASA studies to use small lightweight planes to fly up and down the Valles Marineres. 

It is almost impossible to fly a human scale airplane from the Martian surface because the air is so thin. The take off speed would be too great. But small model plane scale vehicles can be flown and with increasing miniaturization of technology would be useful scouts for exploring Mars.

One of the NASA gliders for Mars, showing how it folds up
One of the NASA gliders for Mars, showing how it folds up

Perhaps in a decade or two we can have astronauts in orbit around Mars controlling avatars like these and others on the surface telerobotically. The avatars would be small and light weight and could be deployed at numerous locations over the surface of Mars. There would also be larger rovers like Curiosity with capabilities for delicate biological analysis. The smaller rovers might bring back samples to the larger ones for analysis, or might help the astronauts to guide them to interesting targets on the ground.


Each crew member would control several avatars on the surface, and "teleport" from one to another, whenever the attention of a human is needed, for driving, piloting, decision making, experiments that need continual supervision and so on.

As well as letting you "teleport", then as technology develops, the avatars can be stronger than humans, more dextrous, smaller to go into tiny caves, never get tired, and they let you fly also, which would be hard for a human to do on Mars. This is like having super human powers, a point that was made in the 2012 Telerobotics Symposium final report.

Everything that the avatars do on the surface is streamed to orbit, automatically with digitally enhanced vision. So you are not dependent on video shot by the astronauts when they feel like it. Everyone sees everything just as the astronauts saw it.

You might easily miss interesting things as you explore Mars. This gives opportunities for someone on Earth to spot it in the video feed back to Earth, right away, or later on. 

So this is another superhuman power. Perfect recall with the ability to re-examine anything you ever saw on the surface.

This would make the whole expedition more engaging for viewers back on Earth. I think a telerobotic mission to Mars would be an exciting way to explore the planet. Using leading edge technology also, and techniques that would interest youngsters who have grown up with such things as video games, omnidirectional treadmills, and avatars in games.

For more about this, see Telerobotic Avatars On Mars With Super-Powers ("Teleporting" from orbit) - Search For Life - And Long Term Exploitation

Yes, the humans never get to stand on the surface of Mars, at least during this exploration phase. But there is something interesting about a place you explore but can never land on in person


This still leaves the option open to colonize Mars. If we do decide to do it then we have all the infrastructure in place to do it, much more safely than today, and with greater knowledge of the planet.

Indeed the idea starts off in the same way as for the Mars Society proposals, as Robert Zubrin himself has looked into possibilities of telerobotic exploration of Mars as low cost early missions to explore the planet and as technology demos.

What we do next can be left for the future to decide.


Meanwhile we can mine resources from the Mars surface and send them to orbit, or use them on the surface to construct factories, industrial plants or whatever. None of this irreversibly contaminates Mars with life.

That's likely to be no problem, so long as we preserve areas of great scientific interest, such as the warm seasonal flows.

We can also grow plants on Mars without contaminating it. The trick here is to use microbe free versions of hydroponics.

You can sterilize the seeds, and so grow plants on Mars with no risk of contamination, so long as you do it with great care. The only thing  that will grow on Mars as a result of this experiment are these plants themselves. So you could grow tomatoes, trees, any kind of large plant you like so long as it can be sterilized and can only grow inside the greenhouses.

Sadly, animals, including humans, can't be sterilized in this same way, or there would be no problem sending humans to the surface of Mars either. If only we grew from steriilizable seeds and could be raised quickly in a microbe free environment, like plants!

Little Prince rover,
"Little Prince" rover designed to support a single plant on Mars. Book cover of "The little Prince" by Antoine de Saint-ExupérySince seeds can be sterilized (unlike humans or animals), these could be grown without any risk of contaminating Mars with Earth micro-organisms.

Named after the "Little Prince" who looked after a single rose on his asteroid in the fictional book by Antoine de Saint-Exupéry

It's possible that plants may be the first living Earth colonists of another planet.

Video of the Little Prince rover


This is a decision we could make, if so then all the infra structure is in place to colonize Mars. We also understand the planet far better than we do now, and understand what the effects of our actions will be. 

This may well save many centuries or decades and prevent many mistakes we would make if we rushed ahead to terraform the planet without studying it in detail first. Especially, it could help us to avoid biological mistakes.

As far as the treaties are concerned, then the Outer Space Treaty prohibits harmful contamination of other celestial bodies. So those who want to colonize Mars would need to establish that the life they want to introduce to the planet doesn't count as harmful contamination. Here harmful is generally understood so far to mean, harmful to the scientific experiments of other sovereign states party to the treaty.

Right now, with so much to be discovered about Mars, it is hard to see how a biological contamination of Mars could be harmless. How could the biological instruments able to detect a single amino acid or DNA molecule work as well in a contaminated Mars as they would do with a biologically pristine Mars?

But later on once we understand Mars thoroughly the situation could well be different.


What if we find independently originated life on Mars, or amazingly interesting evidence of early stages that almost reached life but not quite? Should we leave the planet pristine to avoid contaminating it?

I would say why not? Let's go all the way to Mars, and set up colonies in orbit around the planet, but never set foot on it at all, to avoid contaminating it.

It is a bit like mountains that are left unclimbed out of respect for the mountain or local beliefs. Not too many of those but the mountains in Bhutan over 6000m are unclimbed.

 shea-tang-la), Bhutan
This is possibly the highest unclimbed mountain in the world Gangkhar Puensum with an elevation of 7,570 m. All mountaineering is prohibited in Bhutan since 2004 out of respect for local religious beliefs.

See How Valuable is Pristine Mars for Humanity - Opinion Piece?


Please join the discussion in the comments section below, thanks! Any comments welcome, I only delete obvious spam. It's also okay to go off on a conversational tangent as well, no need to keep strictly on topic in everything you say, as you can see from some of the interesting comment threads on the other pages here. Your comments are treaed with respect so please don't hesitate to comment, whatever your views are on these subjects.