If Elon Musk and Robert Zubrin have their way, we may get migrations of hopefuls setting off from Earth to Mars to colonize what they believe to be a "New World". If so, what they find there will be far more like the nineteenth century Antarctica than the seventeenth century "New World". Indeed, even the climbers who tackled Mount Everest in the twentieth century explored a far more hospitable place than Mars. You could breathe the air on the summit with only the need for an oxygen mask. It's also bitterly cold on Mars - a night in the Martian tropics is colder than the coldest night on Everest in the middle of winter. It's so cold that the air often starts to freeze out as dry ice at night. By comparison, the New World was warm, easily habitable; it was almost a paradise for humans. It had plants, trees, fruit, grew there, animals, soil you could just dig and grow things in. Not only was it inhabitable, it had inhabitants; the North American Indians, Mayans, Aztecs, Inuit etc. It had many new food stuffs as well. Wikipedia has a useful article with a list of New World crops that were native there before 1492 and didn’t occur anywhere else in the world at that time:

Grains: Little barleymaize (corn)maygrasswild rice

Pseudograins: Amaranthknotweedgoosefoot (quinoa)sunflower

Beans: Common beanlima beanpeanutscarlet runner beantepary bean

Fiber: Agaveyucca, long-staple and upland cotton

Roots and Tubers: ArracachaarrowrootjicamaCamas roothopnisslerenmanioc (yuca, cassava)mashua or cubioocapotatosweet potatoullucoyacon

Fruits: Avocadoblueberrycherimoyacranberrycurubafeijoagranadilla or luloguava (guayaba)huckleberrypapayapawpawpassionfruitpepperspineappleprickly pear (tuna)soursop, commercial strawberriestomatotomatillo

Melons: Chayotesquashes (including pumpkins)

Nuts: American chestnutBlack walnutBrazil nutcashewhickorypecanshagbark hickory

Other: Achiote (annatto)cannachicle (key ingredient in chewing gum and rubber), cocacocoacochineal (red dye)logwoodmaple syruppoinsettiarubbertobaccovanilla

Mars not only has no crops or animals, it also has no seas, streams, rivers or lakes, no rain - just ice. It looks Earth-like because it is so dry. The equatorial regions are completely dry almost everywhere too, to hundreds of meters depth. If the planet was covered in an ice sheet meters or kilometers deep, like Antarctica, it would be far more habitable than it is now. It gets so cold at night that the air begins to freeze out as dry ice to form the water ice / dry ice frosts photographed by Viking, for about 100 days of its two Earth years long year.

It also, more fundamentally, has no air either, only 0.6% of Earth’s. The air is a the same pressure as the top of a mountain four times the height of Mount Everest. It has only trace amounts of oxygen. Even with an oxygen mask you would not survive. The moisture lining your lungs would boil making it impossible to take up any of the oxygen and leading to death quickly. You need a full body spacesuit to survive on the Mars surface. And of course any gardening has to be done inside a pressurized greenhouse or habitat holding in tons per square meter of outwards pressure.

Also as a side effect of that, any human occupied habitat  has to be built like the ISS, of tubes and spheres able to hold in the atmosphere against an outwards pressure of many tons per square meter. It also has high levels of radiation. It's not enough to kill you, not nearly. But enough to increase the cancer risk, risk of dying young from cancer too, not late death as for cigarette smoking. It’s like living on Earth after a nuclear war, in levels of radiation.

Saying “let’s colonize Mars!” in my view is like Shackleton saying “Let’s colonize Antarctica!” after his ship sank and he overwintered huddling under boats and killing seals for food.

Dump camp for Shackleton’s party after his boat sunk. Ernest Shackleton and the Endurance expedition, into the pack ice

Antarctica in the nineteenth century was far far more habitable than Mars is for us. Shackleton’s party did survive the winter, hunting seals and huddling under boats. But they didn’t return to England after that experience saying “Great we over wintered on Antarctica - let’s colonize the continent”. Indeed nobody showed any interest at all in colonizing it and eventually they signed the The Antarctic Treaty in 1959 to set it aside for scientific research and such like.

But there are no seals on Mars to eat. Or anything else for that matter. If you can survive on Mars, you can use the same technology to survive in the middle of the driest coldest deserts on Earth or in a floating sea city - using nothing except sea water and air.

I think this analogy with the New World causes unrealistic expectations. Such as the idea that you could be more or less self sufficient on Mars. You could in the New World. Once they knew how to survive there, which crops to grow, how to cultivate the soil, then you could do everything in situ including making your own tools. The American Indians, Inuit, Aztecs, Mayans and the rest of the inhabitants of the New World had been doing these things already for thousands of years. They didn't even need any advances in  technology to survive there. But there is no chance of that on Mars, not with present day technology.

Now whether in the future we will have the technology to be self sufficient in space I don't know. But if it ever happens, we could feed the entire Earth from 2.5% of the Sahara desert using the technology suggested for growing food on Mars or the Moon, or we could feed four times our population from 0.5% of the Pacific in floating self contained environmentally friendly sea cities. That would cost far far less than to feed the same people in space. In a floating sea city, you can leave out much of the complex technology they would need in space, if we do it on Earth instead. You don’t need to wear spacesuits to go outside your habitat to repair it, just open the windows to get air in and let toxic gases escape from your habitat, no need to hold in tons of atmosphere per square meter - hard to beat all that.


Mars is of great value potentially, right away, right now, but not as a place to colonize. It is of great interest for the search for life there. But that means also that we have to take great care not to introduce Earth microbes. Spacecraft on Mars risk crashing, it’s the hardest place to land in the inner solar system. For the reasons see my Why Spacecraft Crash on Mars. A crash of a spacecraft with humans on board on Mars would put an end to any planetary protection of the planet and potentially destroy a lot of the science interest for the search for life there.

That's because, unlike the Moon, global dust storms make Mars into an interconnected system. Microbes anywhere on Mars can transfer microbes to anywhere else, and the dust protects from UV light for a microbe imbedded in a crack and the dust storms themselves reduce the UV levels hugely also. Iron in the dust is good at blocking out UV. That's an observation originally made by Carl Sagan in his discussions of planetary protection of Mars.

The policy so far has been to protect Mars from Earth life. Ideally we'd sterilize our spacecraft 100% and that would make it impossible to introduce Earth life. But because that's too difficult in practice, and because the surface of Mars is so inhospitable so thought not to be easy to contaminate with just a few microbes, instead they reduce the numbers as much as they can before launch, then the travel to Mars reduces the numbers further. As a result they have to use probabilities but they think that it is very unlikely that our microbes on Mars have contaminated it irreversibly. The microbes are just dormant. There is a big difference between a rover that got there in the vacuum and cold of space and pre-sterilized before launch, and a crash of a human occupied spacecraft with trillions of microbes on Mars.

This is not just some obscure academic interest either, some microbe that would only interest specialists. We don’t know what is there so have no idea what we would lose, but it could be the next revolution in biology. To discover a biology based on different principles from DNA life could be the next big discovery in biology after discovery of evolution, and the spiral structure of DNA.

It's not the microbes that need to be protected. It's the discovery of life based on completely different principles potentially. Could be the next big discovery after the double helix. Find out what came before DNA life. Or life that evolved in a different direction. Not Earth microbes. Extra terrestrial microbes. Or early life microbes that no longer survive on Earth.

This life could also be very vulnerable. For instance, one possibility, early forms of life that have been made extinct on Earth. For a while the idea of a shadow biosphere was popular here, that Earth may have remnants of an earlier RNA world still living amongst us. So far nothing like that has been found here. But maybe it has not yet been made extinct on Mars? If so, those lifeforms would be vulnerable to whatever made them extinct here. There are many other ways that potential habitats on Mars could be vulnerable to introduced Earth life.

"Elon Musk and Robert Zubrin just don’t have the right to make a decision like that for the whole of humanity - and not just us, but all future generations and even all future civilizations on Earth. Earth microbes introduced to Mars could never be removed, if there are habitats there for them to colonize. This might rob us and all future generations of major discoveries such as, for example, early precursors to DNA based life.

There are plenty of other places to go, the three top priorities to keep protected from Earth life are Mars, Europa and Enceladus, Ceres also possibly. Let’s not rush our microbes to any of those places as quickly as possible, but find out what is there first.

Let's make our long term objective for Mars, to send humans to Mars orbit and its two moons to explore the surface via telepresence. Let's leave future decisions until we know more about Mars.


I do think we are going to have outposts in space like the ones we have in Antarctica. And we may have larger populations also, tourists, explorers. Maybe eventually self sustaining habitats of thousands, even cities of millions. But it's not like the new world where you just need transport to go to the Moon or wherever and you can make your tools there, grow crops, dig the ground etc. You would need a lot of support from Earth before there is any chance of it being self sustaining.

I think the most likely to be self sustaining are large habitats like lunar caves, which in the low gravity could be as large as kilometers in diameter and over 100 kilometers long - or city domes. Even then the equivalent in habitat volume on Earth would cost much less to build probably (see What about Earth deserts? for examples) - and have less maintenance. But it might be that in the future there's enough reason to be in space to have large numbers there. If so, large enclosed spaces like the lunar caves or city domes would be lowest maintenance. If they can become so low maintenance that the cost per inhabitant per year is only hundreds of dollars, it might even score over habitats on Earth due to the stable conditions, no earthquakes, storms, flooding etc. See my section on Maintenance costs for more on this.

If we want to live in space, the Moon is far closer and easier as a place to start, and it is in many ways more habitable than Mars.

Surprisingly, the Moon is also rather good for gardening. It is no “New World”, but the lunar night is much leses of an issue than you'd think. There's light 24/7 at the poles, and as for the lunar caves, it turns out that many crop plants do just fine with fourteen days of darkness every month provided they are cooled down to a few degrees above zero. While ultra efficient modern LED lightning means the power requirements for the plants that need light during the lunar night are far les sthan you'd think. See my

The Moon also has some commercial potential many think, with possibly hundreds of millions, or billions of tons of ice at the poles, and many millions of tons of CO2, CO, methane, and ammonia. It also has many metals and some think it has platinum and gold from impacts by iron meteorites with some evidence to back them up. Also the Hoyt cislunar tether system (see exporting materials from the Moon) could give a way to return those materials to LEO or to Earth indeed at very little cost / delta v. This involves a couple of orbiting spinning tethers, and is a much lighter and simpler construction than the lunar elevator, though both can be made with existing materials, the Hoyt system is the easiest to build and most practical in the near term.

If so, the Moon could possibly be profitable and if they can turn a profit at all, it might be very profitable, for metals like platinum, supply of ice and fuel to LEO etc, and if so it might lead to people living there permanently (though it might also mean lots of robots on the Moon and a few humans to supervise them). I think it could also be profitable for a tourist industry. There is no guarantee of any of this, but it may be possible.  The New World analogy fails for habitability but in terms of profit, it might well be similar.


The Moon has many resources. As one example, the dust is riddled with nanophase iron. This makes it possible to create glass with about the same amount of energy it takes to boil water, using a microwave. Mars is not like that. The Moon also has high grade vacuum, making in situ manufacture of solar panels very easy, easier than on Earth as you can use techniques that would be prohibitively expensive on Earth. It has many metals and other resources available.

It also has some volatiles at its poles. Probably they got there as a result of cometary impacts, and the polar craters of eternal darkness are the coldest places in the inner solar system, so they have just stayed there ever since. Ice needs to be very cold to not sublimate in a vacuum, but these craters are that cold. As well as water, there's a lot of CO2, CO, and NH3 too, typical compositions for a comet, based on what we know so far at least. The findings are inconsistent about the actual distribution with different ways of measuring it getting different distributions which don't match, which is puzzling. But there is no doubt at all that there are some volatiles there. The main question is about how it is distributed. Estimates so far suggest that there may be a billion tons or more of ice there, and many millions of tons of the other volatiles.

For more on this see these sections of my MOON FIRST Why Humans on Mars Right Now Are Bad for Science

There is almost no commercial potential for Mars in the near future as far as we know. ?The problem is its gravity well, double the gravity of the Moon but by the rocket equation, because fuel is needed to lift extra fuel, it needs far more than double the amount of fuel to get to orbit. And there is no immediate likelihood of a Mars tether to orbit (and Phobos and Deimos orbiting close to Mars would make it a tricky build anyway).

Books advocating Moon exploration and eventual colonization have many chapters about the commercial value. 

Robert Zubrin’s book Case for Mars has one short not very convincing chapter suggesting that intellectual ideas and deuterium could pay for Mars as well as suggesting a colony there could have a role later on supplying materials to asteroid miners in the asteroid belt. I cover those ideas, as well as other suggestions from Mars colonization enthusiasts in my 

 in my "MOON FIRST Why Humans on Mars Right Now Are Bad for Science

I think part of this is unfamiliarity. We are used to the videos of astronauts bounding around on the Moon in their spacesuits. It's obviously a place where you can't just set up home as you can on Earth. In the case of Mars then if you are knowledgeable about science and astronomy, you know that it is just the same. A spacesuit that can protect you on Mars would be the same design as one that can protect you on the Moon. NASA Ames is developing a dual purpose spacesuit that will do for both cases, the suitport which also protects from dust, a problem in both places.

But we don't have actual experience of humans on Mars. It's easy to imagine people just strolling around without spacesuits as in the Barsoom stories, or using light weight spacesuits that are not much more than clothes you put on and off as in so many science fiction stories. The reality is that Mars would be just as tricky a place to live as the Moon. And the Moon has many advantages as it is closer to Earth and its vast lunar caves and the peaks of eternal light at the poles are both unique resources we don't have on Mars. There are caves on Mars too, but in the low gravity of the Moon, the lunar caves may be as large as several kilometers in diameter and over a hundred kilometers long, in theory and the Grail data seems to bear this out so far. See lunar caves.

Yes, let's explore space, send humans throughout the solar system. But as for colonization for its own sake, as for the New World, I just don't see it. At any rate, the Moon is as good a place as any to try out the first attempts.

So, I think we should start with the Moon as the logical next step. It is far too soon to think in terms of colonization. That's like the Antarctic explorers in the nineteenth century thinking they are ready to colonize Antarctica. We should think in terms of exploring like the early Antarctic explorers. In my view, colonizing Mars is unrealistically hard at present as well as having major planetary protection issues. Also the Moon scores over Mars in just about every habitability comparison I've tried, for the peaks of sunlight and the lunar caves. We can experiment with closed systems on the Moon. No need to go to Mars for that. And as explorers humans can explore Mars from orbit via telepresence controlling avatar robots on the surface, go to the Venus clouds, Mercury, the asteroid belt, Callisto and further afield once we have the capability. But until we know more, we need to take especial care with Mars, Europa, Enceladus and possibly Ceres and a few other places because they are vulnerable to Earth microbes, or may well be. And take it from there.

In the process, we may well grow tomatoes and other crops in all those places. For growing tomatoes on the Moon see my An Astronaut Gardener On The Moon - Summits Of Sunlight And Vast Lunar Caves In Low Gravity. It is no "New World" but growing our own food in space is likely to be an important part of space exploration. The ISS mechanical life system works up to about two years but if you are in space for a longer time than that, it makes more sense to grow your own food - and through a rather neat balancing of the equations of photosynthesis and respiration / digestion, if you grow all your own food, you automatically produce all your own oxygen to breathe too.

I'm the author of Case For Moon First and MOON FIRST which explains all this in detail.

See also my science20 articles:

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