For a change of pace, I want to address another common misperception on Quora. These days there's a lot of hype about "going to Mars". A large fortune is being spent on this project. A certain prominent technologist-plutocrat is committing a good deal of his extraordinary hoard of wealth to "making humanity multiplanetary". Many people seem to imagine that colonizing Mars will be relatively easy.
We need to be clear that Mars is an extremely hostile environment; far less hospitable to life than Antarctica in winter. I think it's likely that a human will walk on mars in the medium term (say ~25 years), though I'm no longer sure I'll live to see this. It's very unlikely that humans will successfully colonise Mars and I'm sure no human will ever be born on Mars.
There are three questions to consider when thinking about the project to "colonise Mars":
- Was there ever life on Mars?
- Is there life on Mars now?
- Is there any prospect of Mars sustaining life in the future?
The answers (with come caveats) are probably no, no, and no. Let's look at why.
Past Life.
Mars’ geological (Areological?) history is divided into three main periods:
- Noachian (~4.1–3.7 billion years ago): Heavy bombardment, abundant surface water, widespread clay-rich sediments.
- Hesperian (~3.7–3.0 billion years ago): Declining water activity, formation of extensive volcanic plains, some outflow channels.
- Amazonian (~3.0 billion years ago–present): Cold, dry, low erosion rates, mostly wind-driven surface processes.
While we don't know exactly how life began on Earth, the highest likelihood is Michael Russell's theory that it got started around warm alkaline hydrothermal vents on the ocean floor (see The Rocky Origins of Life 15 April 2016). This process relies on plate tectonics and oceans.
Mars has no plate tectonics and probably never had any. The crust is not made up of mobile plates that converge and diverge creating volcanic and earthquake zones. The crust of Mars is all one big slab of rock although it still has some local deformations and fractures.
Furthermore, Mars hasn't had liquid surface water for at least 3 billion years. So the processes that most likely drove the emergence of life on Earth are absent from Mars. While we cannot definitively rule out past life on Mars, we can confidently say that it is extremely unlikely.
This also means that fossils on the surface will be extremely rare. Fossils are formed in layers of sediment. Mars is known to have some very old sedimentary rocks (generally older than 3 billion years). For reference, the chalk bedrock under Cambridge where I live is only around 100 million years old. On earth, evidence for life in 3 billion year old rocks is rare and often ambiguous, partly because at that time life was bacterial and left few physical traces.
There is some limited geological activity on Mars that creates some localised faulting. Craters and erosion can expose lower layers of rock. The Curiosity rover, for example, has been exploring Hesperian-era sedimentary rocks in the Gale Crater (~3.8 to 3.0 billion years old).
However, once exposed, fossils on Mars would be subject to a variety of powerful degrading processes: including solar and cosmic radiation, chemical oxidation, temperature extremes, and erosion (by dust storms). Microbial fossils are extremely delicate. A fossil on the surface might survive for millions of years, but not billions.
The surface of Mars has been dry, frozen, irradiated, and dusty since the end of the Hesperian, around 3 billion years ago. If life ever existed on Mars, it must have died out at that time. And it will have left few if any traces on the surface.
Present Life
The prospects for present life are considerably less optimistic. Life, as least as we know it, requires favourable conditions. And conditions on Mars have been decidedly unfavourable for at least 3 billion years.
The state of the mantle and core mean that Mars lost its magnetic field about 4 billion years ago (ya). This means that the surface of Mars has been subject to unfiltered cosmic and solar radiation for 4 billion years. Radiation levels on Mars today are ~200 times greater than those on Earth.
This might not be immediately fatal to life, but for Earth-based living things it would cause very high levels of mutations, most of which would be deleterious.
Mars has almost no atmosphere and, thus, no greenhouse effect to speak of. The average surface pressure is 0.006 atmospheres (i.e. 0.6% of Earth standard). Mars' atmosphere is composed of 95% CO₂ and contains less than 1% oxygen, and less than 0.1% water vapour. All life that we know of requires liquid water to survive. While it is true that some tardigrades have survived brief exposure to vacuum, they cannot remain active in those circumstances, they cannot move around, feed, or reproduce in space or on Mars. Surviving is not thriving.
The absence of greenhouse effect and distance from Sol means the average surface temp of Mars is around -65 °C, compared to the Earth average of +15 °C. No life as we know it can survive at -65 °C or below.
There is no liquid water anywhere on Mars and has not been for billions of years. The minimal amounts of water that exist on Mars are solid and have been for billions of years.
What kind of life can survive 3 billion years of extreme radiation and extreme cold, without air or water, and under harsh chemical conditions? None that we know of. None that I can conceive of. And even NASA do not expect to find life anymore. They are looking for fossils.
These are non-trivial barriers to the existence of life on Mars in the present. No one should expect to find life—or fossils of past life—on Mars. Not after 3 billion years of the present conditions. The fact is that the surface of Mars is inimical to life. Which already raises doubts about trying to live on Mars.
Future Life
Despite the very dim prospects of finding life or even past signs of life, technologists and plutocrats seem enamoured of the idea that humans can "colonise" Mars or even can "terraform" it. Indeed, this is presented as an imperative (since capitalists are apparently not planning to stop destroying the Earth's biosphere before it ceases to be able to sustain human life).
The European practice of colonising, privatising, and exploiting resources has given rise to a history of brutality and extreme avarice. I grew up in a British colony and my strongest association with "colonisation" is genocide. Invoking the trope of colonisation ought to ring alarm bells. No good ever came from the urge to colonise.
The problem for human colonisation of Mars ought to be obvious by now: the surface of Mars is totally inimical to life as we know it. A human exposed to the surface conditions on Mars would die more or less instantly. So the main task on Mars would be to prevent any such exposure. This would mean permanently living inside, probably underground.
Being exposed to the high levels of ionising radiation on Mars would cause very high rates of DNA damage, leading to many deleterious mutations. As much as anything it is radiation that would force humans underground on Mars.
The low gravity would prevent normal development of fetuses and infants. Problems like muscle atrophy, bone demineralisation, reduced blood volume, and impaired balance (low g syndrome) would affect everyone. And if your bones never mineralise properly they cannot support your mass. This raises another problem.
A trip to Mars is going to take 6-9 months and 99.9% of that time will be spent in free-fall (microgravity). Which means astronauts travelling to Mars will suffer moderate-to-severe low g syndrome. By the time they get to Mars and 0.38 g, they’ll be seriously ill. Even with an ISS-style exercise regime (+2 hours of exercise daily) they will be severely impaired and liable to broken bones and other health problems. What's more it is not clear that 0.38 g would enough to halt this problem, let alone reverse it. We have zero data on humans living in 0.38 g. And at present, we have no way to get any data short of actually going to Mars.
Nothing we can actually do by way of "terraforming" will address any of these problems.
Terraforming is a science-fiction idea. For example, we see colonisation enthusiasts saying that all we need to do is "drop some comets on Mars" to replace the air and water lost billions of years ago. The obvious problem with this is that the impact of comet-sized objects would throw vast amounts of Martian dust into the thin atmosphere and the low gravity would mean that it took a long time to settle. We have no idea what it would do the Martian crust.
It's all very well casually talking about "dropping comets" but it's another thing being able to accelerate trillions of kgs of ice so that it impacts on Mars. We can just about lob 100,000 kgs into orbit. How are we going to handle a load that's at least a billion times more massive?
The fact is that we have no way to alter the trajectory of a comet such that it would precisely impact on Mars. It's not just that it's too expensive (which it would be). It's not that we fall just short of the technology required. Even if we could spare the trillions of dollars it would cost, there's no way we can change the trajectory of any comet. As a rule of thumb, the rocket fuel required to substantially change the orbit of a comet would have the same order of magnitude of mass as the comet.
If we tried to use nukes, the water we delivered would be highly radioactive.
In practice, there's no way to do it; and even if there was, we couldn't afford it.
People talk about seeding Mars with genetically engineered superbugs that will somehow flood the atmosphere with Oxygen. But even if Frankenstein's algae could convert all the Martian CO₂, it would take a very long time because of the cold, and it would still only amount to a partial pressure of ~0.0000013 atmospheres of oxygen. Which is effectively zero and still instant death for a human trying to breath on the surface.
Worse, there's nothing on Mars that would make the expenditure of trillions of dollars worthwhile. There is nothing on Mars that we could not obtain on Earth for a fraction of the cost. Or from robotic mining of asteroids. Those trillions of dollars would go a long way to solving the existential threats we face on Earth that plutocrats are currently in denial about.
Conclusion
The conditions on the surface of Mars—low g, high radiation, near-zero air and water—are inimical to life and have been for around 3 billion years. Dating back to the time of the last universal common ancestor of life on earth.
The geological processes that gave rise to life on Earth are conspicuously absent from Mars. Because of the lack of plate tectonics, the surface we see on Mars is billions of years old.
There's little or no reason to believe that Mars ever supported life. And even if we stipulate that it might have existed, there's little or no reason to believe we will find fossils of past microbial life since these are either deeply buried or severely degraded.
The idea of terraforming is quite entertaining in speculative fiction and, at a stretch we might allow that it is possible. In practice, terraforming is not remotely technologically or economically feasible.
I can imagine visitors to Mars. I'd love to live to see this. But I cannot imagine colonies on Mars ever being viable. The problems involved are fatal and practically insurmountable.
Earth is unique in being the only planet we know of that supports life. There is no planet B.
Capitalists appear to think that they can shit where they eat with impunity. They appear to believe that destroying the Earth is a fair price to pay so that a few men can be pampered as though they were gods. They seem to believe that they can simply go and live in space once the earth is destroyed. But these fantasies are not remotely realistic. Without Earth, we are all dead.
Here's a radical idea:
Let's not destroy the only planet that we know can sustain life.
~~Φ~~
