I just watched this evening a program on TV about Mars colonization, featuring a class of hyper enthusiastic teenagers, Bill Nye the not science guy, and Carl Sagan's protege, Neil DeGrasse-Tyson.
Everybody was just so certain that we absolutely had to go to Mars, primarily because it would be so cool!! Eleventy!!!
One "expert" claimed it was just essential that thousands and perhaps millions of humans would one day live on the Red Planet. He seemed to believe it was simply inevitable.
However, there are actual real world and serious reasons that will never happen. Here are some of the most compelling.
1. The Martian atmosphere is super thin. So thin that in an Earth laboratory, it would be considered a vacuum. Step out of a space ship on Mars without a sturdy spacesuit, and in seconds every liquid in your body would boil and you'd drop down dead.
Suffer a hole in your suit, and the same thing happens very quickly. Not human friendly by any means.
2. It's cold. Really cold. Check out the weather station on the rover Curiosity, which is near the equator, and you can see just how bad it is. Over a hundred degrees Fahrenheit below zero at night, and maybe 75 during a warm day. That's also a huge temperature swing. That is not a friendly environment for humans or basically any Earth life form except for maybe some weird bacteria, not to mention the wear and tear on mechanical devices.
3. The soil is toxic. It has high levels of percolates and gypsum, and would need to be decontaminated to grow food. Further, the dust is the consistency of flour, and would be exceptionally hard to keep out of the living and working quarters of any Mars base. It's effect on humans after being breathed or swallowed is unknown.
4. Radiation exposure. On the trip out, which would take a couple of months, the greatest threat to astronauts would be galactic cosmic rays--or "GCRs" for short. These are particles accelerated to almost light speed by distant supernova explosions. The most dangerous GCRs are heavy ionized nuclei. They're much more energetic (millions of MeV) than typical protons accelerated by solar flares (tens to hundreds of MeV). GCRs barrel through the skin of spaceships and people like tiny cannon balls, breaking the strands of DNA molecules, damaging genes and killing cells.
How much of this can a human body take? Nobody knows.
Further, Mars has no magnetic field and little atmosphere to protect from the UV rays of the sun. Without it, the storms and flares sent out by the sun nail the planet hard, and protection would need to be supplied. How much radiation from a strong solar flare could make it to Mars is unknown so far, but on Jan. 20, 2005, the International Space Station was struck by a proton storm from a flare so powerful that its crew had to take shelter in the bulkier Russian side of the station, in a section designed with such storms in mind.
5. Low gravity. In zero G's, it is well known that bone and muscle loss occurs quickly. There are also some negative impacts on vision. Gravity on Mars is about 40% that of Earth, and it will be zero G's on the way there and back. How much effect this would have on colonists longer term is unknown, but certainly negative.
6. Distance makes resupply and availability of spare parts very difficult. If there is an emergency breakdown - and everything would have to be very complex to make a colony work - then spare parts and tools would need to be there, as resupply from Earth is months away. Medical emergency? Months away from help, at best. Major problem, like the machinery to heat the colony breaks (remember, nights get down to 100 degrees below zero), and help is months away.
Our rovers, with a couple of exceptions, have had a short life on Mars due to the hostile environment. Imagine the problems and risks of trying to plant a whole colony, even a small one, on the surface and make it stick.
To make all this even remotely possible, backups with backups with backups would need to be planned for and constructed, and then transported from Earth to Mars. That would be astronomically expensive (pun intended). Getting the money would be a huge problem.
7. Crushing boredom once there. 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 color as the ground. It will be hard to distinguish different colors and everything would look much the same.
Further, because of the dust problem and risk issues, trips outside would necessarily be minimized. You'd tend to be stuck inside a small living and working environment, with the only view a bland, monochromatic landscape devoid of any living thing from a small porthole like window.
8. Contamination of Mars. It is almost inevitable that a colony on Mars will contaminate the planet with Earth micro-organisms. 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. Anything could and likely would release some of those, through air leaks from the habitat or a space suit, waste, accidents, or from simply unknown means.
Some of those Earth life forms might be able to reproduce on the surface, particularly lichens, and some hardy micro-organisms, or 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.
Contamination would make it hard or impossible to tell whether or not any of the life forms found on the planet were 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, since some of these tests are sensitive enough to detect a single amino acid in a gram of soil.
If contamination is shown to have occurred, back on Earth you would be known as the people who irreversibly contaminated Mars. You would probably get negative press for doing that, and through all the future of human history would probably be known as the humans who contaminated Mars rather than the first to colonize the planet.
Finally, there's also the possibility that escaped Earth life forms 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 could return to the habitats, still retaining their abilities to survive in a human habitat, but with extra capabilities from their evolution on the surface of Mars. A small, but not impossible risk, and one that must be considered.All in all, it's clear that contrary to those who enthusiastically root for Mars colonization, like hucksters Bill Nye and Neil DeGrasse-Tyson, it will be nearly impossible to finance the trip and the engineering of a safe and predictable colony construction, and the physical and psychiatric risks to the astronauts, no matter how happy they are to go, will be unpredictable and unacceptable. Finally, there is the risk to Mars itself from the nearly inevitable contamination from the astronauts themselves.
It's a no go, no matter what you hear on TV.