[...] 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. Today’s automated spacecraft are not only strictly more capable than human astronauts, but cost about a hundred times less to send (though it’s hard to be exact, since astronauts have not gone anywhere since 1972).

The imbalance between human and robot is so overwhelming that, despite the presence of a $250 billion International Space Station National Laboratory, every major discovery made in space this century has come from robotic spacecraft. In 2023, we simply take it for granted that if a rocket goes up carrying passengers, it’s not going to get any work done.

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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. It also adds support to the theory that life may have started as an interplanetary infection, a literal Venereal disease that spread across the early solar system by meteorite. If that is the case, and 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.

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The chief technical obstacle to a Mars landing is not propulsion, but a lack of reliable closed-loop life support. With our current capability, NASA would struggle to keep a crew alive for six months on the White House lawn, let alone for years in a Martian yurt.

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.

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Even if you don’t care about contamination, NASA is required by treaty to care, and that has severe consequences for mission design. It means human landing sites will intentionally be kept far from anything interesting. The phenomena of greatest scientific interest on Mars (gullies, recurrent slope lineae, intermittent methane sources, and underground water) will all be off-limits to astronauts. So will terrain features like caves or lava tubes that could conceivably shelter life. The crew will not live in a Martian pueblo, but something resembling a level 4 biocontainment facility. And even there, they’ll have to do their lab work remotely, the same way it’s done today, raising the question of what exactly the hundreds of billions of dollars we’re spending to get to Mars are buying us.

(I omitted all the footnotes; see the blog post for them.)