Mars is a fascinating planet, the most like Earth of all the planets in the solar system, and may help us to understand much about the origins of life on Earth. Undoubtedly, it's a wonderful place to explore, especially with augmented reality vision. But though it was quite Earth-like in its first few hundred million years, it is not at all Earth like now. Earth remains by far the most habitable place in our solar system. The most inhospitable places on Earth, such as Antarctica, even in the depths of winter, and at the centre of the continent, are far more habitable than anywhere else in our solar system. Space colonies and the poles of the Moon, are both more easily habitable than Mars, and more easy to make self sufficient. Why is that? Read on to find out more.

You see so many news stories about the possibility of humans colonizing Mars, and many readers may get really excited by the idea. But few of these stories mention the many drawbacks and downsides of human colonization. I thought it might help redress the balance to talk about this.

1. Cold

You would agree that the center of Antarctica in winter is cold, not the best of places to set up home? Well Mars is far colder. At the Curiosity site, which is close to the equator, typical night time temperatures are -70 °C. Occasionally it drops to below -100 °C. It is often cold enough for the CO2 in the atmosphere to freeze out as dry ice. A human couldn't survive those temperatures without technology.

Antarctica from space (NASA) - this is far more hospitable than Mars. Mars would also be covered in ice, the only reason it isn't is because it is so dry that there is only enough water to create the polar ice caps, and the air is so thin that water ice sublimes directly to water vapour whenever temperatures rise briefly above 0C.

It gets warm at midday, briefly, can go over 0 °C. So is not cold all the time, but has these huge temperature swings of 70 °C between day and night, just about every day. You can check the current Mars weather for Curiosity. Dry ice for comparison melts at -78.5 °C.

It might not look as cold as Antarctica because it has ice only at the poles. But that's because of the thin atmosphere. Over most of the surface, ice sublimes directly to water vapour without ever turning liquid. There is also not much water vapour. As a result it is extremely dry near the equator, cold enough so that it would have a permanent ice cover, like Antarctica, except that it is too dry, and the atmosphere is too thin to support it.

If you are just looking for new land which can be made habitable for humans to live in, it makes much more sense to colonize Canada, or Siberia, or the Inner Hebrides of Scotland (where I live) or indeed the sea bed, than Mars. BTW this is a rhetorical question, I'm of course not actually proposing that any of these places are colonized, as they are already sovereign territory - except possibly the sea bed in international waters. For undersea colonies, see The Long, Ongoing Dream of Undersea Colonies, and Atlantica Undersea Colony

If you are keen to set up a space colony, then a colony close to Earth, closer to the sun, and without the night time shielding effect of a planet would be like the tropics compared to Mars. Why colonize Antarctica first, when you can colonize the tropics?

2. Vacuum

Yes Mars does have an atmosphere, it's true. But it is so thin, it would count as a laboratory vacuum on Earth. For most purposes, you might as well be in space or on the Moon.

A human would need to put on a spacesuit to survive the low pressure, never mind the lack of oxygen. The pressure is so low, your saliva and the moisture coating the interior of your lungs would boil. The average Mars surface pressure is well below the 6% Armstrong limit which absolutely is the limit for human survival. Average surface pressure is about 0.6% of Earth sea level. A leak in your spacesuit would kill you quickly. No oxygen to speak of either.

The atmosphere does have some benefits, as a source of CO2, but even then, is low pressure so has to be pressurized to be useful. In a space colony, then you could make CO2 from the carbonaceous near Earth asteroids; it's not that hard to find ways to make it in space if you expand your habitat e.g. with greenhouses and need more atmosphere. So again that's not a major benefit over space or the Moon.

3. The "it's been done" syndrome

Okay I know that Mars hasn't "been done" yet. But many explorers who want to colonize Mars have as their main motivation that it is new. They aren't interested in colonizing the Moon, because it has already "been done". They just want to be the first people on a new planet. If that's your motivation, then remember, as soon as the first colonists arrive on Mars then it will already "be done". For a colony to survive it would need massive support from Earth, billions of dollars every few years.

Those of us who lived through the Apollo landings will remember how much excitement there was about the first landings - and then within just two or three years, it became boring to the public, to see astronauts on the Moon, because "it has been done already". Apart from occasional moments of human interest such as the first time a golf ball was hit on the Moon, the general public lost interest totally and the news dropped to the back pages of the papers.

Apollo mission to the Moon, victim of the "it's been done" syndrome. Is this not still an exciting place to explore, does it matter that it has already been visited by humans?

The same would surely happen with colonists on Mars. Just as the Moon may seem boring to you now, well same would be true of Mars after a few years.

4. Dust and Dust storms

Every Martian summer, roughly every two Earth years, you get a higher chance of global dust storms. These can last for weeks, and the light from the sun drops by over 99%. Here is a photo showing progression of a dust storm as seen by Opportunity.

Progression of Mars dust storm over three days, Opportunity Rover

During the dust storms, then artificial light is needed in middle of the day to grow crops, and you won't be able to see anything. Solar power won't work.

As a minor point, the dust itself may be hazardous to humans. Some studies showed that moon dust may be somewhat hazardous - not as much so as asbestos, but enough to be of concern. Mars dust may be similar (we don't know its constitution well yet).

This last issue may be addressable however. The surface of Mars is covered in dust. However, the suitport should help prevent explorers from bringing it into the habitat.

Not much you can do about the dust storms though except artificial lighting and just sit them out.

5. Contamination

It is almost inevitable that a colony on Mars will eventually contaminate the planet with Earth micro-organisms. At current levels of technology, I don't see how that can be avoided. A human is host to about 100 trillion micro-organisms in 10,000 different species. A habitat would have many other micro-organisms too, in the food, in the soil, other supplies, and floating in the air.

Some of those may be able to reproduce on the surface, particularly lichens, and some hardy micro-organisms, polyextremophiles that may be able to survive in marginal habitats of cold salty brine that may form around deliquescing salts in the morning and evening. See my Might there be Microbes on the surface of Mars?. Some of these can do just fine in human habitats but have surprising hidden capabilities to survive in extreme conditions. The rovers are sterilized to prevent contamination - humans can't be.

Now if you aren't a scientist that mightn't bother you much. But back on Earth you would be known as the people who irreversibly contaminated Mars. You would probably get a fair bit of negative press for doing that, and through all the future of human history would probably be known as much as the humans who contaminated Mars as the first to colonize the planet. For some idea of the potential value of a pristine Mars see How Valuable is Pristine Mars for Humanity - Opinion Piece?

This would make it hard or impossible to tell whether or not any of the life forms you find on the planet are introduced Earth life or native (many micro-organisms on Earth are poorly characterized). It would also complicate experiments to look for trace biosignatures in the deposits on Mars, some of these sensitive enough to detect a single amino acid in a gram of soil.

The contamination could also affect your water supplies. There's also the possibility that it could evolve on the surface through adaptive radiation into new forms hazardous to humans, because the conditions are so different (strong UV, cosmic radiation etc). These then could return to the habitats some years later, still retaining their abilities to survive in a human habitat, but with extra capabilities from their evolution on the surface of Mars.

Some sources for contamination include

  • Habitat not completely self contained - e.g. maybe you need to dispose of human wastes outside the habitat - or some chemical builds up which needs to be vented to the exterior.
  • Spacesuits leak. The problem is - that the more flexible the spacesuit, then the more joints it has, and these continuously leak air. Could you contain micro-organisms within the spacesuit without them leaking out of the joints?
  • Suitport. Astronaut climbs into the spacsuit through the hatch. It does leak a small amount of air still, about a cubic foot. The spacsuit itself would also leak air constantly, all present day suits do, e.g. through flexible areas such as the joints.Airlock. It may be possible to do something about this, but no-one has yet designed an airlock that vents no air at all out of the spaceship. The suitport gets close to this, but is designed more to prevent dust getting into the cabin than to prevent air getting out. Some air would still escape, about a cubic foot in the current design of the suitport.
  • Accidents. E.g. spacesuit breached in an accident on the surface. Or one of the spaceships crashes during landing. Even if crew survive, the hull may be breached and contaminate Mars with the micro-organisms inside the habitat. If anyone dies, then that is a major contamination right away.

What it amounts to is that to contain contamination we would need to land a biohazard laboratory on Mars, with the crew and all its contents as the biohazard to be contained and kept away from the surface of Mars. We don't have the technology to do that yet at a reasonable cost. Indeed I'm not sure it is possible at all with present day technology when you take account of possibilities of accidents and hard landings.

There is also the possibility of life already on the planet. Some scientists think there may be life on the surface even now in the harsh conditions there. If so, there is a remote possibility that it might be hazardous to humans. Could be a pathogen like Legionaire's disease which we are not immune to. Could be that it infects other micro-organisms so infects micro-organisms within the habitat. Or could be an allergen for humans, e.g. when you breath in the micro-organisms into your lungs. This chance is probably very low, but not impossible. It's been reviewed many times by biologists, and so far, no-one can really say for sure, they can't go so far as to say that it is impossible based on the scientific knowledge of Mars so far.

6. Unproven technology for self contained habitats

This also applies to space colonies too, but I suggest that it is best to work on this in space colonies close to Earth first, where you can deal with emergencies more easily.

  • The ISS is not at all self contained. They can't even wash their clothes, but get new clothes sent up when they need clean ones. All the dirty ones are disposed of in the supply vessels which burn up in the atmosphere.
  • Overview of the ISS environment control system, which requires complex technology, and has many inputs and outputs and is not a closed systemHuman waste products can be problematic in a small habitat. Though urine can be recycled, without too much trouble, excrement is much harder to deal with and in the ISS is again disposed of in the supply vessels.
  • Atmosphere regulation is hard in an enclosed habitat. In the ISS there is a complex environmental regulation system which filters out many different harmful gases that can build up in an enclosed human system (that includes ammonia, hydrogen cyanide, acetone, hydrogen chloride, nitric oxide, carbon monoxide as well as carbon dioxide and many others) and keeps the oxygen levels right. If this goes wrong in the ISS (as has happened several times) you can send replacement components or emergency oxygen from Earth but on Mars you would be in trouble.
  • Micro-organisms are problematical in an enclosed habitat. This is something the Russians found out with Soyuz. In the ISS many measures are taken to keep the numbers of micro-organisms low, including keeping the atmosphere very dry and filtering them out. Still they have occasional build ups of biofilms. (For an overview of this issue see Microbial Colonization of Space Stations)

All of this is solvable but requires complex machinery to keep it going. There are ideas for self contained habitats using natural methods, such as Biosphere 2, the ESA's Mellisa and the Russian BIOS-3 but these are larger than the first habitats, and again is not 100% proven technology for space yet.

Biosphere 2, first large scale attempt at a self enclosed biosphere type habitat
Biosphere 2, first large scale attempt at a self enclosed biosphere type habitat. The experiment was a failure but much was learnt and in future it may be possible to set up totally self contained habitats in space. The technology is not mature yet however.

7. Hard to make self sufficient - need for parts and supplies from Earth

Yes there are lots of resources available on Mars. But they are available in space too, mining the NEOs. Mining on Mars will be hard to do, as hard as in space. You still need to use space suits because of the vacuum conditions. And however much you can make from native Mars materials, at least at present levels of technology, then many components and replacement parts will have to come from Earth.

Opportunity, in Endurance crater, the longest lived rover sent to Mars, has lasted since 2004, well beyond its original design lifetimeNone of our rovers on Mars have lasted for very long, except for Opportunity which has been active since 2004 (it's sister rover Spirit stopped working in 2010).

Human habitats presumably would be rated to last longer than that. Yet, the habitats would be extremely complex technologically. Things would go wrong eventually, and you would need parts from Earth.

It seems unlikely that you could really supply all the food by plants grown on Mars, and if you were able to do that, yet sometimes crop failures would surely occur, especially early on. Again this needs food to be supplied from Earth.

Medicine would be needed too, and other supplies that need high levels of technology.

The habitat would have many complex machines to maintain the temperature and the atmospheric conditions. Spacesuits are also complex mechanisms that could fail, and that the colony would be surely unable to make, and only able to do some repairs for them.

Especially, you are totally reliant on the heating units, and the atmosphere regulation units in your habitat, without them you die.

There is no way a Mars colony could be totally self sufficient in the near future - except with some game changing technology such as nanoscale 3D printing or self replicating nano-technology.

8. Boring landscape to unassisted human eyes

The landscape on Mars may seem quite stunning in some of the photos. But these have been digitally enhanced with the white balance changed, to help geologists to recognize rock types. To human eyes it is a dull reddish gray or brown. The sky is the same colour too. It will be hard to distinguish different colours and everything looks much the same.

Shows effect of natural colour (centre) and processed to resemble Earth lighting conditions (right)

You probably wouldn't get much chance to explore it directly for safety reasons and because it takes so long to put on your spacesuit. Mainly you would just see the view from your window whatever that is. You would soon get tired of the dull gray landscape and skies.

9. Accidents

Okay so accidents happen. On Mars they may well be fatal if they result in damage of your spacesuit or habitat.

10. Mars is too small to be worth colonizing

Yes I know the surface area of Mars is large, comparable to that of Earth. But there are several other consequences of such a small planet.

  • Cosmic Radiation - high levels, would need to limit the amount of time you spend on or near the surface without protection from the cosmic radiation - otherwise you have an elevated chance of getting cancer.
  • Low gravity - so far it's not known whether humans can remain healthy long term in a Mars gravity. Same is true for the Moon but is easier to return sick astronauts from the Moon to Earth, e.g. if it is found that bone loss is as bad in low gravity as in zero g. There have been many biologically surprising results for zero g, and there may be surprises for low g as well.

    "Inevitable Descent" by Pat Rawlings - astronaut landing on Mars. It's not yet known if an astronaut can remain healthy long term in a low gravitational fieldIssues astronauts encounter in zero g include, bone loss (in zero g is about 1% per month), muscle atrophy (about 5% per week to start with), blood loss (about 22% within a few days, could be a contributing factor for heart atrophy). Many of these clear up on return to Earth; as a rule of thumb it takes one day to recover for every day in orbit. But the evidence so far suggests you might not recover from bone loss completely. You can easily lose 20% of your bone mass in a long duration space flight. Long term you can get serious vision problems too, one third of astronauts returning from space have impaired vision and in one case the impairment was permanent.

    We have no way to truly simulate less than 1 g for long time periods on Earth. It might be completely safe for humans but again it might cause long term problems like zero g.
  • UV radiation - has hazardous levels of UV radiation, again have to be careful about exposure.
  • Atmosphere not recycled through continental drift. This is mainly relevant for long term prospects. On Earth CO2 which gets captured in the seas eventually recycles to the surface through continental drift and volcanoes. If we were somehow to find a way to introduce an atmosphere to Mars it probably wouldn't last long in geological timescales - unless some alternative cycle can be set up.
  • Surface area is far less than for space colonies - if you thought the surface of Mars was large, well space habitats potentially have much more space available. See my post Asteroid Resources Could Create Space Habs For Trillions; Land Area Of A Thousand Earths. So we shouldn't get too hung up on the large surface area of Mars, as it's not the only place we could colonize.

Okay all of those can be addressed, protection from cosmic radiation, centrifuge sleeping quarters and indeed the whole habitat could be set spinning to increase the gravity felt inside, and UV radiation easy enough to protect against. The area for colonization is comparable to Earth so only seems small in comparison to space colony potential.

But it all contributes to make Mars not quite as enticing as it would seem at first.

Colonizing closer to Earth first

I'll not go into this in any detail here, as it rather strays from the main topic of this post, and I've covered it in Asteroid Resources Could Create Space Habs For Trillions; Land Area Of A Thousand Earths. But in short the amounts of resources available to build space colonies just from the Near Earth Objects (NEOs) is surprising. There is easily enough material in NEOs to build habitats with many square kilometers of living area, and with just about all the materials we need to make them.

Longer term, space colonies have more potential for human habitation than planetary surfaces - and that is iincluding the Earth itself. There is enough material in the asteroid belt to build colonies with the land area of a thousand Earths.

Nerius is a likely target for materials for a space colony, as it is one of the larger NEOs to get to, and easier to get to than the Moon. Though only 300 meters across, it has enough material for cosmic radiation shielding for three square kilometers. of space habitats following the design of the Stanford Torus. Mars's small moon Deimos has enough to shield an area more than twice the size of Switzerland (e.g. as lots of Stanford tori). Then, when you get to the asteroid belt, there is enough material there for cosmic radiation shielding for a thousand times the surface area of Earth. This is a different idea from the idea of hollowing out the asteroids which creates much less living space, Nerius could only make a 300 meters diameter habitat if you hollow it out.

In the nearer term the most habitable surface areas of any celestial body in the solar system outside of Earth are probably the poles of the Moon, where there are the "peaks of (almost) eternal light" that get constant year round light. This would give near constant solar power and light for greenhouses except during eclipses. They are also right next to the craters of eternal night which are thought to have deposits of ice and are the coldest places in the inner solar system. So a fascinating place to explore and live, and with just about all the materials you need to build a small near to self sufficient colony.

The peaks of (almost) eternal light might need to be explored scientifically using rovers first to minimize contamination, for instance maybe there are layered deposits of ice preserving a record of the history of the early solar system and the solar winds. That exploration could be done by humans too, however, by telepresence. The moon is far enough away from Earth for telepresence exploration from L1 or L2 to be worth doing.

NASA artwork from the 1970s for the Stanford Torus design
Stanford Torus Interior (NASA), population 10,000, NASA space colony art from the 1970s

This was something we could build already with 1970s technology and would be far easier to build today. Also, we would have sufficient resources to build this using materials from just one small NEO such as Nereus (perhaps the most accessible of them all, 300 meters across and easier to get to than the Moon in terms of delta v). It has enough material to provide cosmic ray shielding for about 3 square kilometers of habitat living area. There are many other NEOs comparable in size or larger.

One would of course start smaller, but eventually colonies of this size and larger could be constructed, mainly with use of resources available in space within easy access from Earth.

Other colonies could be in the other Lagrange locations, or orbit the Earth or co-orbit the sun with the Earth. Long term, a location close to the Earth makes for faster trade both ways, and permits space tourist visits. Shorter term it also makes for easy assistance and backup in case of emergencies, and astronauts can if necessary be returned to Earth within a day or two.

Also, technical assistance for near Earth colonies can be given by experts on Earth in close to real time without the light speed delays of Mars. In the near term, just because of unavoidable communication delays from Earth during emergencies, I think that explorers who travel as far as Mars would probably have the best chance of success if they are experts who have "written the manual" on the spaceship systems, together with scientific experts able to make fast real time decisions about experiments on the surface.

For more about all this see my Asteroid Resources Could Create Space Habs For Trillions; Land Area Of A Thousand Earths.

Solution to all of this for Mars - telepresence

So, I'm not "against mars colonization". Would be great if these problems could be solved and maybe with some future technology they could be. Perhaps self healing spacesuits and spaceships, able to hold in contamination even in a hard landing or accident? Perhaps some successor to the suitport that is self cleaning and lets no air escape at all? Or we might find out things about Mars that lead us to decide that it is okay to introduce Earth micro-organisms to it.

But in the meantime, space colonies would seem to make much more sense than a Mars surface colony. But Mars is such an interesting place to explore especially for scientists. With enhanced vision, the boring landscape would become interesting to look at and explore. And our mechanical rovers on Mars are so slow, experiments take months to complete, and they do in a month what a human could do probably in an hour.

So, what can we do? Well the answer is telepresence. The technology is developing rapidly, both through the games industry, and through various applications such as remote telepresence surgery (surgeons in the USA operating on patients in France for instance), and field geology especially deep wells.

With humans in orbit around Mars, then they could explore the surface with telepresence. You get super human abilities too, as you can build telerobots able to fly (hard for a heavy human to do in the thin Mars atmosphere), or smaller or stronger than humans.

Video of Robert Michelson's entomopter.

On Mars it might be easier for machines to fly with insect type flight with rapidly beating wings, using the bumble bee wings vortex effect for lift. On Mars that can work scaled up to wings a meter across because of the thin atmosphere also assisted by the low gravity. That's the idea of the entomopter. One way you could build telerobots able to fly on Mars.

With several rovers spread out on the surface of Mars you can "hop" from one to the other in virtual reality, set up experiments, set them going to return to them later, or drive around on the surface of Mars in real time. The robots would be semi-autonomous, not just sit around doing nothing, but a bit like the game of civilization, you set them going doing various tasks then pop over to another place on Mars to take over another robot, and so on.


Image from the Telerobotics Symposium held in 2012, one of the recommendations was that telepresence be used to explore Mars during the early orbital missions.

Eventually we might have a sizeable colony in orbit around Mars and a sizeable "colony" of telerobots on the surface which might make materials for export to the orbital colony or indeed to Earth.

Telerobots could do mining, and all the things envisioned for a human surface colony, with almost no risk of contamination, either of Mars, or back to Earth of any micro-organisms on Mars.

As an astronaut, you could explore the surface within your spaceship in a shirt sleeves environment, no need to put on your spacesuit. The orbital spaceship would spin for gravity, probably using a tether system in early versions of the colony. With an onmidirectional platform and telerobots on the surface, you could walk and run over the surface too, as if you were there but with enhanced vision and capabilities.

We could actually grow plants on the surface of Mars too by telepresence, since seeds can be sterilized. There are two types of hydroponics, and sterile hydroponics doesn't use micro-organisms, instead supplies all the nutrients the plants need in the water. Aeroponics is a version of hydroponics especially useful for space missions which uses minimal water as the roots grow in moist air.

We could have greenhouses on the surface, and export the food to orbit using fuel also created on the surface of Mars.

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

Later on, if the decision is made to send humans to the surface, you already have the telerobots there and whatever technology is associated with them, for the humans to use for their habitats.

See also

Then, on same subject as this article but a more leisurely treatment: