A few months ago, I found myself deep in a conversation about Mars colonization timelines. The other person — a software engineer, genuinely enthusiastic, not naive about the engineering — was walking me through radiation shielding approaches, the habitability of lava tubes, the logistical case for SpaceX’s Starship architecture. It was fascinating. He clearly knew far more than I did about the technical specifics. But somewhere in the middle of it, a question started forming that I couldn’t quite place, until eventually I did: we hadn’t once asked whether any of this was a good idea.
We had been talking about how for an hour, and neither of us had said the word why.
That conversation has been sitting with me since. Not because the technical questions aren’t important — they’re genuinely hard, and the people working on them are doing serious work. But there is a gap between “this is technically possible” and “this is what we should do,” and that gap tends to close faster in the Mars discourse than it does almost anywhere else. The survival problem gets all the oxygen. The ethical one gets treated as settled — as if the answer to “should we go?” is obviously yes, and the only thing left to figure out is the radiation shielding.
I’m not a space scientist and I don’t have a strong stake in any particular answer here. What I do have is a persistent discomfort with how questions get framed — with the way the tractable problem has a tendency to absorb all the attention that the harder one deserves.
The question we’re not asking
The survival discourse is, in its way, extraordinary. Cosmic radiation at the Martian surface running at roughly six to seven chest X-rays per day under normal conditions — and significantly higher during transit and solar storm events. An atmosphere that amounts to about one percent of Earth’s. Temperatures swinging 70 degrees Celsius or more between day and night. The progressive bone density loss from low gravity that compounds across months into something that isn’t easily reversed. These are real problems, and the engineers working on them deserve the coverage they get. None of that is what I’m questioning.
What I’m questioning is the habit of treating “can we survive there?” as a proxy for “should we go?” — as though answering the first settles the second. It doesn’t. They are different questions that require different kinds of thinking, and we have, for the better part of a decade, let the excitement and tractability of the first crowd out serious engagement with the second.
The life question nobody wants to stop for
One of the more uncomfortable things I’ve come across in reading about this is the planetary protection question — specifically, the possibility that Mars might not be as empty as the colonization narrative tends to assume. The debate about whether Mars currently harbors microbial life, perhaps in briny subsurface water or in the recurring slope lineae that have been periodically interpreted as evidence of seasonal liquid water, remains genuinely open. No confirmed biology has been found. But “not yet confirmed” is not “not there,” and the question of what we would do if we found it — before or after we arrived — seems to get less serious treatment than it warrants.
NASA’s planetary protection guidelines exist precisely because this uncertainty is real. They were built around the concern that Earth microbes carried on spacecraft could contaminate Mars and compromise any future ability to find or study native life there — or vice versa. The protocols apply most strictly to robotic missions, which can be sterilized. They apply far less cleanly to humans, who exhale, shed skin cells, and carry an internal ecosystem of trillions of organisms that are not optional passengers. A crewed mission, by design, cannot be managed the same way a probe can.
What this means, if taken seriously, is that any crewed mission to Mars before we have higher confidence about the biological status of the planet carries a non-trivial risk of introducing an extinction event for whatever might be living there. Carl Sagan, who spent his career both advocating for space exploration and urging caution about it, made this point repeatedly — that introducing Earth organisms into a low-diversity Martian ecosystem, if one exists, could eliminate it entirely before we ever knew it was there. The argument has not aged out. If anything, growing scientific interest in Martian subsurface habitability has made it more pressing, not less.
We have spent years asking whether humans can survive on Mars. We have spent much less time asking what Mars might be surviving from, if we arrived.
The backup civilization argument and its hidden premises
The most common justification offered for Mars colonization at the level of civilizational stakes is the backup argument: a multi-planetary species is an insurance policy, and the cost of not going is existential risk to the entire human project. Stephen Hawking made this argument in his final years. Elon Musk has built it into the explicit ideological foundation of SpaceX’s long-term mission — a self-sustaining city on Mars as a hedge against collapse on Earth.
I find this argument more worth taking seriously than most critics give it credit for. The underlying concern about existential risk is real. The logic that a species concentrated on one planet is more vulnerable than one distributed across two is coherent. But the argument is doing more work than it usually admits, and some of its hidden premises deserve more scrutiny.
The most obvious one is timing. The existential threats most likely to end civilization on Earth in the foreseeable future — climate change, engineered pandemics, nuclear conflict, biodiversity collapse — are immediate relative to any realistic projection of a self-sustaining Martian colony. A genuinely self-sustaining Mars city, by most serious estimates, is generations away. The threats we are failing to address are not. If the backup civilization argument is meant to be taken literally as a response to existential risk, it would seem to require securing the primary civilization first — not as an alternative to Mars ambitions, but the sequencing matters considerably more than the discourse tends to acknowledge.
The governance question matters here too. The Mars colonization effort as it currently stands is being driven largely by the decisions of a very small number of extraordinarily wealthy individuals and their companies, operating mostly outside democratic institutions, international treaty frameworks, or any serious mechanism of public deliberation. The Outer Space Treaty of 1967 prohibits national sovereignty claims over celestial bodies, but it was not designed to address private colonization by corporations operating under whatever regulatory minimums they can find. The choices being made now — when to go, at what pace, under what protocols — will shape the terms of Mars activity for a very long time. The fact that those choices are being made by a small group of people with specific and concentrated interests seems like something a more serious public conversation would address.
What an honest accounting would require
I want to resist the easy conclusion here — the “we should never go” position that treats any Mars ambition as inherently reckless or hubristic. There are real arguments for human Mars exploration. The science alone — the geology of ancient riverbeds, the evidence of a once-warmer world, the complex chemistry of the regolith — has produced discoveries with no parallel in the history of planetary science, and there are legitimate cases that humans on the surface could accelerate that science in ways robots fundamentally cannot. I find the impulse to go, the sheer ambition of it, genuinely compelling on some level I can’t entirely defend rationally.
But I think we owe it to the question — and possibly to whatever might be living on that planet — to stop treating the survival problem as a substitute for the ethical one. An honest accounting would start with the life question: invest seriously in determining whether Mars is biologically empty before a crewed mission departs, and treat a positive finding as a real constraint on what comes next rather than a footnote to manage. It would include meaningful international deliberation about who gets to make these decisions, and why the current answer to that question is “the people with the most rockets.” It would take the backup civilization argument seriously enough to notice what it actually implies about sequencing and urgency on Earth.
The conversation I had a few months ago was a good one. The engineer was genuinely thoughtful, and I learned things I didn’t know. But I’ve been bothered, in the time since, by how naturally we both moved through the technical questions and how completely we both skipped the other kind. The “can we?” problem is captivating in a way the “should we?” problem never quite is. It has cleaner edges. It has milestones. It announces itself as progress.
The harder question doesn’t do any of that. It just sits there, waiting for the conversation to slow down enough to make room for it.
