Mars Vs. Venus
How we make decisions about technological development
How much do we really know about the other planets in our solar system? Even just our two closest neighbors, Mars and Venus?
Venus typically conjures harsh images of the inhospitable outcome of millennia of runaway greenhouse effect. The surface temperature is 872 degrees Fahrenheit (467 degrees Celsius). That's hot enough to melt lead instantly. The atmosphere is so thick, the pressure on the surface is 90 times higher than sea level on Earth. That's the equivalent to being one kilometer deep in the ocean. The atmosphere of 96% carbon dioxide is unbreathable. Clouds of sulfuric acid cover the entire planet which routinely unleash acidic rain onto the surface in violent storms. The surface of Venus may be even more inhospitable to humans than the surface of Mercury, despite being almost twice as far from the sun.
Given this, who would ever consider a human mission there? The Soviets sent several missions to Venus, the Venera missions. The longest one of these landers was able to maintain operation was Venera 13 at 127 minutes. So when the likes of Elon Musk, Richard Branson, Robert Zubrin, or Buzz Aldrin suggest that humans should create settlements on Mars, it seems almost common sense. Not only is it our planetary neighbor but, of the rocky planets, it seems the only one even remotely suitable for human life.
But that isn’t necessarily true. NASA’s High Altitude Venus Operational Concept (HAVOC) outlines a possible architecture for human missions to our nearest neighbor. While the concept is mostly used as a training tool for out of the box analytical thinking rather than a serious proposal, it nevertheless demonstrates that such a mission could be technically feasible if the same level of investment and effort were put into it as has been put into Mars.
The foundational basis of HAVOC is that, while the surface of Venus is one of the harshest environments in the solar system, the atmosphere 50 km above it is more suitable. A lighter-than-air hibatate sitting at that altitude, just above the sulphuric acid clouds, would exist in relatively mild conditions. The average temperature at this altitude is 167 degrees Fahrenheit (75 degrees Celsius). While this is hotter than the hottest temperature ever recorded on Earth, it is well within the capacity of human engineering to build suits and habitats for. Certainly it is no more of a challenge than -81 degrees Fahrenheit (-63 degrees Celsius), which is the average temperature on the surface of Mars.
Further advantages abound. Atmospheric pressure at that altitude is about the same as sea level on Earth. Mars has only 1/100 Earth’s atmospheric pressure. We’ve discussed the structural challenges of withstanding internal pressure before. We’ve also discussed the problems of power generation on Mars. Solar panels on Mars would, on average, generate half as much energy as on Earth. It is likely that any major attempts at settlement there would require nuclear power. But at an altitude of 50 km on Venus, solar panels would generate about 1.5 times as much energy as on Earth.
A mission to Venus poses fewer challenges to astronaut health as well. Because Venus is similar in size to Earth, it also has a similar gravity. On the other hand, Mars’s ⅓ gravity poses risks of circulatory and musculoskeletal degeneration. Though it does not have a magnetosphere, Venus’s ionosphere provides substantial protection for solar radiation. It would be similar to living near the north pole of the Earth. Mars, on the other hand, would subject an astronaut to 40 times the daily radiation exposure of the average American. This is dangerous in the long term, and would require mitigation for extended stays on the planet.
At this point you might be thinking that I’ve skipped over an important detail. Sure, conditions may be better, but how the heck is habitat supposed to suspend itself 50 km into the air on Venus? In fact, this is possibly easier than landing on Mars!
In addition to being the most habitable altitude on Venus, 50 km also happens to be the altitude at which the atmospheric composition of Earth at 1 atm (the pressure at sea level) is buoyant. In other words: a light enough module filled with regular old air would float there on its own. Landing on Mars has also historically been a very fraught endeavour. The success rate is currently about 50%. Gravity on Mars is still enough to make crash landings catastrophic. But the atmosphere is too thin to slow down approaching landers. Engineers have had to come up with elegant but extremely complicated solutions to the Mars landing problem. The Mars Science Lab was lowered to the ground by a hovering sky-crane, which had to launch itself away upon touchdown so that when it crashed it didn’t destroy the lander! The Spirit and Opportunity rovers inflated into giant balloons when they crashed into the ground so that they would survive, bouncing up to 12 meters into the air and flying as far as 200 meters per bounce during the landing! A testament to human ingenuity, to be sure, but probably not what future Martian astronauts want to experience! Designing a habitat that floats when filled with regular air is not likely to be any more of an engineering challenge.
So if sending astronauts to Venus could be just as feasible as sending them to Mars, why has there seemingly been no serious consideration of doing so? There isn’t just one answer. It is mostly a combination of two factors: economic and historical. From an economic perspective, the greatest risk to extraterrestrial human settlement, aside from engineering failures, is the reliance on Earth. A settlement that must get supplies from Earth to survive is always at risk if those supplies don’t arrive. This could be an error that destroys or delays the supplies in transit, or it could be the loss of political will to continue to spend the money to send those supplies. Escaping Earth’s gravity is no easy feat, and doing so is expensive. Therefore, a settlement that can mine, refine, and grow its own supplies is less likely to simply be canceled due to the cost of supplying it. Surface settlements simply mitigate this risk more. Not to mention those same resources offer a greater chance that the owner of the settlement **cough Elon Musk cough** could make a lot of money.
The simple explanation of the historical perspective is: we’ve just kinda always thought about Mars as being inhabited. In 1894 the astronomer Percival Lowell explained the observed markings on the surface of Mars as a global irrigation system built by an intelligent civilization. While his claim lacked scientific credibility, it ignited public imagination. HG Wells published “War of the Worlds” only 3 years later. Martians have been a cultural staple ever since. Burroughs’ “Princess of Mars,” Welles’ radio adaptation of “War of the Worlds,” Flash Gordon, Henlein, Bradbury, and even Looney Toons all include Martians.
Scientific priorities reflect the place Mars has in the popular imagination. For scientists, study of the red planet offers potential insights into habitability and the development of life in the universe. Despite the fact that no life has yet been found there, some scientists believe that Mars is the origin of life on Earth. Literally dozens of missions have gone to Mars, many with the intent to search for signs of life or at least the potential that it once existed there.
None of these missions have found life on Mars, either living or long extinct. Mission after mission launches to the red planet with this goal, and again and again fails to find what they are looking for. None of this, however, seems to deter continued investment into further study of Mars. Mars Sample Return (MSR) represents the pinnacle of this seeming obsession. Complexity, budgets, and timelines ballooned. The project went $5B to $11B, and from a 2026 launch date to as late as 2040. Things got so bad that congress stepped in to reduce NASA’s planetary science budget, and the mission threatened to consume nearly all other planetary science supported by NASA. I don’t recommend bringing up MSR at planetary science conferences unless you want to be in the middle of an argument.
That isn’t to say that all of these missions and Mars science has been worthless. Quite the contrary, we know more about Mars than we do about our Moon, the closest celestial body the our Earth! These missions have given us invaluable insight into the formation of Mars, its history, and its geology! But that's just the point. Mars seems so promising, in part, because we’ve sunk so many resources into learning about it. Would Venus actually be the obvious choice for human missions if we had invested resources more evenly?
The situation is much like that which I described between metal and wooden airplanes. When metal airplanes were first developed, they did not, in fact, outperform wooden airplanes even along those metrics which their proponents argued were superior. But due to ideas about metal being more futuristic, engineers continued to pour time and money into solving the material and mechanical problems of metal airplanes until it became true that they were superior. Skip forward to today, and metal has itself been largely replaced by composite materials, which are very similar to the wooden composite used in the last great wooden airplane: the de Havilland Mosquito. If engineers had pursued the two technologies in more equal measure, perhaps we would have learned about the benefits of composites sooner, and perhaps discovered something even better. Who knows where we might be in terms of material and aviation technology today!
Or consider nuclear power. Initially, the Atomic Energy Commission (AEC) explored a variety of different nuclear power technologies. But Admiral Rickover eventually selected light water reactors because they could be developed quickly, and the US had a large quantity of enriched uranium from the weapons program. The companies that developed and manufactured reactors for submarines didn’t want to pioneer a whole new technology for civilian reactors. They already knew a lot about light water reactors due to the time and resources put into their development by Rickover. So they developed light water reactors for civilian use as well, without fully understanding whether that was the best or even most economical nuclear technology for that use.
The situation for human missions to other planets shows much the same phenomenon. Mars seems like the best candidate because we understand it the most because we’ve put the most time and effort into it because it seems the most habitable. And on and on.
Philosopher of technology Langdon Winner describes what he calls “technological somnambulism.” He argues that our ability to evaluate technology lags behind our ability to innovate new technology. Scientists, engineers, and capitalists are very good at thinking of, creating, and applying new technologies or existing technologies in novel ways. But we are quite bad at understanding the kinds of consequences those new technologies are likely to have. We don’t yet have a good way of understanding where those technological pathways will lead us. And so, when we get to a fork in the road of technological development, rather than deliberate the best path, we simply wander onward in whatever direction seems easiest. We might as well be sleepwalking.
This concept should sound familiar, as we’ve discussed its consequences before. Both Taylor and I have recently written about the consequences of LLMs for higher education. While Taylor’s outlook was worse than my own, we both agree that no one took adequate time to think about how LLMs would impact teachers. We have sleepwalked into this problem.
Thus, we often allow past decisions to dictate future choices. Just like how we continue to study Mars, to get samples from Mars, and to send humans to Mars even as potential alternatives go unexplored. We do not know enough about places like Venus to say whether or not they could be better. Nor did we know enough about alternatives to light water reactors to make an adequate comparison. When we sleepwalk through the process of deliberation about the development or adoption of new technologies, through the process of selecting which pathways we should take, we allow ourselves to live in a dictatorship of the past over the present.
 | A guest post by
|
Good article. I especially liked the call-backs to nuclear power and plane construction. In reading the end, I was reminded of this: https://en.wikipedia.org/wiki/Asilomar_Conference_on_Recombinant_DNA