Maciej Cegłowski writes:
Unlike the Moon, which hangs in the sky like a lonely grandparent waiting for someone to visit, Mars leads a rich orbital life of its own and is not always around to entertain the itinerant astronaut. There is just one brief window every 26 months when travel between our two planets is feasible, and this constraint of orbital mechanics is so fundamental that we’ve known since Lindbergh crossed the Atlantic what a mission to Mars must look like. . . .
We shouldn’t send human beings to Mars, at least not anytime soon. Landing on Mars with existing technology would be a destructive, wasteful stunt whose only legacy would be to ruin the greatest natural history experiment in the Solar System. It would no more open a new era of spaceflight than a Phoenician sailor crossing the Atlantic in 500 B.C. would have opened up the New World. And it wouldn’t even be that much fun. . . .
It wasn’t always like this. There was a time when going to Mars made sense, back when astronauts were a cheap and lightweight alternative to costly machinery, and the main concern about finding life on Mars was whether all the trophy pelts could fit in the spacecraft. No one had been in space long enough to discover the degenerative effects of freefall, and it was widely accepted that not just exploration missions, but complicated instruments like space telescopes and weather satellites, were going to need a permanent crew.
But fifty years of progress in miniaturization and software changed the balance between robots and humans in space. Between 1960 and 2020, space probes improved by something like six orders of magnitude, while the technologies of long-duration spaceflight did not. Boiling the water out of urine still looks the same in 2023 as it did in 1960, or for that matter 1060. . . .
Mars is also not the planet we took it for. . . . The surface might be dry, but in most places there was water ice just underneath. Dynamic surface features hinted that water (or at least brine) was flowing to the surface from deep underground. . . . The news from the ground also got better. Arriving at Gale Crater in 2012, the Curiosity rover found itself looking at an ordinary lake bed, complete with organic sediment and odd stick-like structures that would be called fossils if we found them on Earth. The crater had been habitable for millions of years in the past, and something in it was still emitting methane at night. Over in its own crater, the Perseverance rover found complex organic molecules of indeterminate origin.
But the really exciting news for Mars was the discovery of unexpected life on Earth. . . . not just dozens of unsuspected microbial phyla, but two entire new branches of life . . . These new techniques confirmed that earth’s crust is inhabited to a depth of kilometers by a ‘deep biosphere’ of slow-living microbes nourished by geochemical processes and radioactive decay. . . . This underground ecology, which we have barely started to explore, might account for a third of the biomass on earth.
The fact that we failed to notice 99.999% of life on Earth until a few years ago is unsettling and has implications for Mars. The existence of a deep biosphere in particular narrows the habitability gap between our planets to the point where it probably doesn’t exist—there is likely at least one corner of Mars that an Earth organism could call home. . . . if our distant relatives are still alive in some deep Martian cave, then just about the worst way to go looking for them would be to land in a septic spacecraft.
But the fact that a Mars landing stopped making sense has not had the slightest impact on NASA’s plan to go there in a rocket-propelled terrarium.
And more:
The chief technical obstacle to a Mars landing is not propulsion, but a lack of reliable closed-loop life support. . . . The technology program required to close this gap would be remarkably circular, with no benefits outside the field of applied zero gravity zookeeping. The web of Rube Goldberg devices that recycles floating animal waste on the space station has already cost twice its weight in gold and there is little appetite for it here on Earth, where plants do a better job for free. I would compare keeping primates alive in spacecraft to trying to build a jet engine out of raisins. Both are colossal engineering problems, possibly the hardest ever attempted, but it does not follow that they are problems worth solving. In both cases, the difficulty flows from a very specific design constraint, and it’s worth revisiting that constraint one or ten times before starting to perform miracles of engineering. . . . The only way to explore Mars in our lifetime is to ditch the requirement that people accompany the machinery. . . .
In recent years, there’s been a remarkable division in space exploration. On one side of the divide are missions like Curiosity, James Webb, Gaia, or Euclid that are making new discoveries by the day. These projects have clearly defined goals and a formidable record of discovery.
On the other side, there is the International Space Station and the now twenty-year old effort to return Americans to the moon. These projects have no purpose other than perpetuating a human presence in space, and they eat through half the country’s space budget with nothing to show for it. Forget even Mars—we are further from landing on the Moon today than we were in 1965.
In going to Mars, we have a choice about which side of this ledger to be on.
This all makes sense. I’ve never thought much about this Mars mission thing because it’s always seemed like a bit of a joke. But if powerful people are really gonna try to use this as pretext to take a big chunk out of our national resources, then, yeah, it’s good to have people like Cegłowski pushing back.
This seems contradictory, and was not in the link (I had to go to part one). But makes me wonder how we can calculate the energy balance of the earth without accurate numbers on the biomass (which is taking input energy and storing it in chemical bonds).
I have to agree. The leap from one third (or to be precise, what “might” be one third) to 99.999% is a huge one.
I still agree with the thesis that a mission to Mars (and crewed spaceflight in general) is a waste of resources. So it’s unfortunate to see these gratuitous errors (or at best, hyperboles) undermine the strength of the conclusions.
Maybe it’s 1/3 of the mass but 99.999% of the organisms?
Likely. Consider the biomass of trees versus tiny insects, or even more so, microbes.
I agree that something seems wrong. Here is the first sentence of the abstract of a 2024 review article (https://doi.org/10.1093/ismejo/wrae091): “The terrestrial subsurface hosts microbial communities that, collectively, are predicted to comprise as many microbial cells as global surface soils.”
That’s from the first part of the essay, entitled “Why Not Mars,” and it points out that, while there are about 12,000 known species of microbes, DNA sequencing has indicated that there might actually be close to a trillion microbial species, and a footnote does note that this estimate relies on a whole bunch of assumptions but it does have two further references from which the estimate was taken.
I’m generally not a fan of these it’ll-never-work-out takes given the incredible success of NASA (disclosure and humblebrag: I’m interning there now). From the admin to the lowliest interns, I don’t think anyone here takes these moonshot (or Mars-shot) missions lightly. They’re about growing up to meet the challenge. Yes, the tech isn’t fully developed… yet. But it never was fully developed for earlier Apollo missions. The assumption of using “existing technology” is so odd to read about. And even 7 days on Mars would be a real learning opportunity, never mind the inspiration to lead children into STEM.
Jay:
Fair enough. If Nasa can make the case for its budget, that’s fine with me. I just want the case to be made, if it’s going to be done.
One very key question is “how much budget”?
There is zero chance of Mars happening with traditional space costs and methods. But if new rockets and new companies can make the cost of doing things in space radically cheaper, that changes.
Right now is sort of a tricky time to discuss this; in a year we should have significantly more information (how has SpaceX Starship development gone?; did Vast’s Haven-1 – supposed to be the first private space station – launch as planned?; did Blue Origin recover smoothly from their launchpad accident and successfully launch their Mark 1 Moon lander?; how is the Artemis III hardware progressing?)
I really wish you luck. I was very inspired watching the moon landing as a kid. I built model rockets and sketched them in my notebooks while not paying attention to how boring school was. And I wound up becoming a scientist. So that can work despite it being a rather indirect way to spend money on science education.
When we went to the moon, NASA went to over 4% of the US federal budget. Now it’s at 0.2%. The FY2027 proposal asks for another 25% cut, but congress didn’t go for the last one. Assuming the Wikipedia page is correct, that is:
https://en.wikipedia.org/wiki/Budget_of_NASA
I’m a little skeptical of the side effect argument, as I’ve heard the same thing about war, and I don’t want to fund wars just to get better airplane navigational guidance. I’m also worried that any money we try to spend on space exploration will be diverted to private companies rather than being used for the public good.
I’m genuinely curious as to what people think we’d learn from putting people on Mars for 7 days that we didn’t learn from launching a rover. But then I have to admit that I don’t know what we learned from putting people on the Moon, either. I seem to remember that Teflon was developed for the Apollo program. Asking Gemini, it doesn’t mention Teflon, but it tells me medical imaging, memory foam, cordless tools, space blankets, fire-resistant fibers, plus food safety standards, water purification, and fly-by-wire. It’s not clear to me that the equivalent amount of spending wouldn’t have led to similar innovations without going to the moon.
Not surprisingly, my memory was fine in that I had heard that Teflon was invented by NASA. It turns out that NASA were just consumes of Teflon and Velcro, not inventors.
https://www.thenakedscientists.com/articles/interviews/myth-nasa-invented-teflon-and-velcro
Realistically, you don’t go to Mars for 7 days; the launch windows don’t work out that way. The short version (opposition class) is more like one month, while the long version (conjunction class) is far longer.
The problem is, spending on what? I don’t think you necessarily know ahead of time what you will end up inventing. In hindsight, you could have just picked the winners, and saved a lot of money. But you didn’t have the hindsight when you started.
I would argue that one of the pragmatic purposes* of space exploration is that it gives a non-destructive goal to sustain technology development, in the way war historically has done.
*Though I would also argue that the primary purposes are non-pragmatic. Same for things like the Large Hadron Collider; no conventional return on investment is to be expected.
The Large Hadron Collider provided a big return on investment: in addition to dotting the is and crossing the ts in the standard model, it showed that the string theory types were simply wrong: the universe doesn’t work that way.
Unfortunately, said types didn’t get the message, and just added a few more orders of magnitude to their theory to make sure it couldn’t be disproven.
But the argument that “science by pork barrel” can provide stuff that real science might not is, I think, not a defensible theory, since it means that stuff that really does have a good chance of being useful might not get done. Said more succinctly: scientists aren’t idiots, but politicians are.
My favorite counterargument: Milly D’s group* at MIT wanted to do magnet work, but the University of Florida got the pork barrel magnet lab, so Milly D’s group invented graphene instead, Scotch(TM) tape being cheaper than superconducting magnets.
*: https://en.wikipedia.org/wiki/Mildred_Dresselhaus
Physics theories being proven true or false isn’t what I meant by “conventional return on investment” – that’s not really an economic benefit and doesn’t directly affect people’s quality of life.
(I do absolutely believe pure science has value anyway, but I would argue that’s not the kind of value that is objectively demonstrable to people with differing values. One could say the exact same thing about human exploration, or indeed art, or…)
@David
There are many things wrong in what you wrote; for one you might like to read https://en.wikipedia.org/wiki/Discovery_of_graphene
“I don’t know what we learned from putting people on the Moon, either. ”
We learned that Hasselblads are seriously great cameras. Which the rest of us had already figured out*,**.
*: https://pbase.com/davidjl/image/119152038
**: https://articles.anseladams.com/story-of-moon-and-half-dome/
“I don’t think anyone here takes these moonshot (or Mars-shot) missions lightly.”
You never heard of Elon Musk then?
Elon Musk isn’t part of NASA.
He has a lot of influence in the government, and is a main NASA contractor. Do you really believe NASA is insulated from political meddling? Then I have a data center on the moon to sell you…
Oh, he definitely has very significant influence, but that’s not the same thing as NASA believing Musk’s more extreme claims. NASA is not acting like they’re expecting a future with thousands of Starship flights in the next few years.
There is a question whether the current administration is serious about going to the moon anyway. After all, in the last admin, VP Mike Pence was adamant that a five year plan to reach the moon by 2024 had to be achieved ““..failure to achieve our goal in the next five years is not an option”. How did that go?
Now things are seemingly on the boil again. It’s instructive and chastening to listen to former NASA administrator Jim Bridenstine testifying before Congress about the Artemis program and it’s extraordinary labyrinthine structure. He isn’t giving the impression that this has a good chance of suceeding – in fact he says it’s highly unlikely that the US can land on the moon before China. His relevant testimony starts at around 28:30 mins in and is a good listen:
https://www.youtube.com/watch?v=MgYo-WO4xFs
Shedloads of public money is being transferred to the corporate sector though, and maybe that’s the point.
Not to mention that Martian soil is high in perchlorates, at levels toxic to humans and plants, and Martian dust has a composition that makes it pose a high risk of causing lung diseases, including cancer, if inhaled by humans. The Wikipedia article on Martian regolith provides a good brief summary of this: https://en.wikipedia.org/wiki/Martian_regolith#Toxicity. For a podcast treatment of this issue and some of the issues raised by Cegłowski, there’s a good discussion with astrophysicist and science journalist Adam Becker on YouTube:
A Physicist Destroys Elon Musk’s Mars Fantasy – YouTube
https://www.youtube.com/watch?v=NOm_ucvQKRY
Becker is the author of the 2025 book, “More Everything Forever: AI Overlords, Space Empires, and Silicon Valley’s Crusade to Control the Fate of Humanity.” Becker sees the Mars settlement vision as of a piece with the tech oligarchs’ promise of salvation from major human problems via investment in AI. He calls it “the ideology of technological salvation.” NY Times published a good review of the book, if you’d like to see a capsule summary of his arguments.
See also Kelly and Zach Weinersmith, “A City on Mars: Can We Settle Space, Should We Settle Space, and Have We Really Thought This Through?”
https://en.wikipedia.org/wiki/A_City_on_Mars
But wait, there must be intelligent life on Mars. You don’t see the Martians wasting tens of billions of dollars needed elsewhere, risking lives, and potentially endangering the environment of both Mars and Earth trying to send their inhabitants on a valueless trip to Earth.
Eh, I don’t agree with the science/tech side of this. (The “what should we be spending money on” question is much harder to tackle objectively, so I won’t touch that. I also don’t agree, but the reasons why I don’t agree are based on things much harder to usefully debate).
The SpaceX Starship program is far enough along now that it can’t really be ignored in this sort of discussion, and with super heavy lift capacity closed loop life support stops being a major limiter for Mars – since you can bring enough consumables that really good closure is not necessary.
As for life on Mars … we won’t contaminate it in any destructive way. Mars’ surface is clearly not inhabited by a biosphere in the Earth sense, or it would be obvious (massive chemical disequilibrium in the atmosphere, like oxygen on Earth). Any life that exists will be deep subsurface, presumably in isolated pockets, thus really hard to contaminate. And also pretty nearly impossible to discover by automated means. Robotic deep drilling on another planet isn’t really practical, InSight had troubles and that was way simpler.
As for “farther from reaching the moon than we were in 1965″… I think that’s hard to sustain after Artemis II, unless one has a strong reason to expect *both* Moon lander contracts (SpaceX and Blue Origin) to fail. Sure, Blue Origin just had a rocket explosion, but those aren’t really rare.
“since you can bring enough consumables that really good closure is not necessary” — I don’t think you’ve thought that through. Becker discusses the work done on the resource needs for a supplied consumables approach. SpaceX conjectures it would be enough to transfer 1 million tons of cargo and 1 million people to Mars (by 2050!), but that scenario relies on “In-Situ Resource Utilization (ISRU)” to produce fuel, oxygen, and construction materials locally. So that huge delivery of consumable is just to set up the closed-loop system you are hoping to avoid. You would have to ship enormously more supplies—continuously—if the Mars settlement is not nearly entirely closed-loop. These issues are explicitly addressed in the critical discussions linked in previous responses.
I was discussing an exploration mission not settlement. With zero closure a human needs roughly 5kg of life support consumables per day (about 1kg oxygen + 1kg food + 3kg water), so for a crew of four and a mission duration of 700 days you’re looking at about 12-14 metric tons of consumables. That’s well within what’s reasonable for a Starship sized vehicle.
Realistically you’d have some level of closure above zero, though possibly not a very aggressive one, but it’s not actually *required*.
Yes settlement needs ISRU. But ISRU is not closed loop! It is taking external resources and using them, not endlessly recycling the same resources.
What about fuel?
Not sure I understand the question.
The mass of fuel would be vastly larger than the mass of life support consumables.
If you mean producing fuel by ISRU… with a super heavy lift rocket that’s not necessarily required. It might or might not make sense depending on other choices in the mission architecture. The NASA DRM style proposals are pretty radically different from what SpaceX has suggested. And there’s ideas like Aldrin cyclers too.
I mean, 12-14 metric tons of consumables is all well and good, but if you need a lot of fuel, then the weight goes up massively. So then the mission seems a lot less feasible.
That’s kind of a different issue. My point was that closed loop life support isn’t actually the limiting factor, unlike what the article claims, since it’s not actually needed.
As for huge amounts of fuel … The key question (which should be answered within a year or two, since Blue Origin, SpaceX, and the NASA/Rocket Lab/Eta Space LOXSAT project are all working on it) is whether cryogenic refueling in space works out. If so, and if you have a cheap heavy or super heavy launch vehicle (both Starship and New Glenn hope to be that), huge amounts of fuel is no longer a problem.
Ultimately we should know within a year or two.
I actually think the likelier reason a human Mars mission doesn’t happen is lack of appetite for risk + focus on a new Moon race. The kind of architecture NASA is trying for the Moon should be extendable to Mars, but that doesn’t mean it will be used that way.
What are you putting the oxygen in, and how much do the containers weigh?
In compressed oxygen tanks, just like you would on Earth.
Sure the tanks add mass, but if you have a “Starship class” lander (~100 tons) for a crew of four or six, you’ve got lots of mass margin.
I really think the limits are money and risk acceptance, not purely technical.
Ignoring SpaceX is impossible, but Starship hasn’t even reached low earth orbit yet. NotSpaceX put six crews on the moon 50 years ago. NotSpaceX put robots on Mars 50 years ago. NotSpaceX has had robot rover Curiosity trucking around Mars for 14 years (to the date).
Yeah, NASA has done a lot of things SpaceX hasn’t.
I think Elon Musk claims a lot of things that are incredibly implausible, and some which border on actually impossible, but the reason SpaceX is relevant here is that they *may* dramatically reduce the cost of doing things in space.
It’s true Starship hasn’t reached a full orbit yet… but the flight that’s supposed to do so is scheduled for the end of this month / possibly early September. It could fail, of course, it’s a test flight… but this is a bit of an awkward time to have this discussion because a *lot* of relevant stuff is supposed to be demonstrated in the next year. And not just by SpaceX… NASA’s LOXSAT should launch this year, Vast’s Haven-1 is supposed to launch Q2 2027, Blue Origin’s Mark 1 Moon lander is likely a similar-ish timeline (was supposed to be end of this year but delayed by the New Glenn pad accident), etc. Artemis III is theoretically mid-2027 but I’m skeptical of that timeline.
It might be interesting to come back to this discussion in August 2027.
On “what we learned from Artemis II”:
My take was that we learned that space radiation was somewhat worse than we thought, and that missions significantly longer than Artemis II would be unreasonable. Then there’s the question of solar particle storms…
Also, microgravity is bad for you, in lots of ways. Kidneys, muscle, eyes, brain all sustain damage. And Mars’ gravity (38% of Earth’s) isn’t enough to support human life, let alone achieve the partial recovery (e.g. the risk of kidney stones doesn’t fall) we see in astronaughts returning from space.
It looks to me that putting humans (other than Elon Musk) in space gets stupider by the day.
Ceglowski covers this: we actually have no experience of humans living in fractional gravity except the Apollo missions. Its possible that Lunar or Mars gravity is much healthier for humans than free fall, or that it brings a different suite of horrible health problems. This is not a problem you can solve with bigger rockets, you need human experiments and if the results are bad your timeline has to slow down. Another of his points is that if your plans rely on multiple decades of congressional funding, you probably do not want to tie yourself to the most controversial US president since Andrew Jackson. I’m neutral on crewed spaceflight by 2100, but I have trouble taking seriously a crewed Mars mission in the next ten years.
Is he serious about life forms having been found on Mars???
I believe the statement is that the discovery of deep endolithic life on Earth increases the plausibility of life on Mars. Which is probably true, but I think somewhat off the point, because deep endoliths don’t really interact with the surface so a surface mission wouldn’t contaminate them.
We are being told on the one hand that humans will shortly be replaceable here on Earth by AI and robots, and on the other that it is essential that we send humans to the Moon and Mars, not just robots. Strange times, indeed.
Kenneth:
Yes, good point!
As much as I don’t believe the first part, some people find human exploration to be valuable in itself for reasons other than pure science or economics.
Like climbing Everest “because it is there”.
“valuable in itself for reasons other than pure science or economics.”
Climbing Everest is really not “valuable” in any meaningful sense. It is simply a form of recreation for people looking for extreme challenges, and there are many such people, and as long as they don’t do damage that’s fine with me (but they do damage), but it’s absolutely not “valuable” for anybody else.
The “Humans on Mars” obsession is similar. There is no plausible case for humans on Mars because any potentially worthwhile exploration would be better left to robots. And the possible satisfaction this kind of “exploration” might give to deranged individuals really should not justify the expense. Apart from the fact that these individuals very likely won’t survive such a mission given current technology.
I mean ‘valuable’ in the sense that (certain) people do in fact value it, as shown by their risking their lives to do it, and many other people are interested in it.
Kenneth:
True and we are being told that by exactly the same people.