To be honest, I believe in the future of space colonization because I want to believe in it. It’s romantic. It’s adventurous. It is super! It’s also, at worst, a way to preserve the species in case we destroy the Earth—and deus ex humana to save ourselves, even though we might not deserve it under the circumstances. I’m a big fan of the Artemis and Project Gateway missions, which could begin construction on a space station in lunar orbit by the end of the decade, and a manned mission to Mars in my lifetime. I dream about what’s behind it, because dreaming is good and healthy. There are countless technological hurdles in the way that are worth tackling in their own right: We proceed scientifically by determining which challenges can be overcome.
But what if certain challenges are not obstacles but roadblocks, not technological but biological? If the problem is not what we can build, but what we are? It would be a huge blow to future hopes of a space diaspora if the obstacles were not about time and distance, but about the fundamental weaknesses of the human body. We’ve long known the harmful effects spaceflight can have on the human body: bone loss, anemia, weakened immune systems, increased risk of cancer, the list goes on. Some problems are caused by microgravity; others by background radiation from space—NASA estimates that astronauts are exposed to the equivalent of up to 6,000 chest X-rays. Astronauts in low Earth orbit, where the International Space Station hangs, are partially shielded from this radiation by the Earth’s magnetosphere, but they too suffer from these effects.
Add to these effects the potentially catastrophic: The universe is screwing up our kidneys in a big way.
The study, ominously titled “Cosmic Kidney Disease” and published last week in The nature of communication, examines the kidney function of 66 astronauts who spent up to 180 days on the International Space Station, which is relatively safe compared to a return mission to Mars that would take several years and expose the astronauts to more intense deep space radiation. But even this limited time really took its toll on the astronauts. The study found a significant deterioration in kidney function and a higher risk of kidney stones, which is the result of the shrinking of the kidney tubules. This, you don’t have to be a doctor to realize, is bad. And the damage could be permanent after long enough—the study simulated the effects of prolonged exposure on mice, and their kidneys never recovered.
Even more harbingers of a lengthy mission is that the effects won’t start to show until it’s too late to prevent them. “If we don’t develop new ways to protect the kidney, I would say that even if an astronaut could get to Mars, he might need dialysis on the way back,” said Dr. Keith Siew, lead author of the study. “We know that the kidneys show signs of radiation damage late; by the time it shows, it’s probably too late to prevent failure, which would be catastrophic for the mission’s chances of success.”
NASA is well aware of the need for radiation protection, especially higher-energy galactic cosmic rays, on any manned interplanetary mission and is exploring potential solutions. One way to protect yourself from cosmic radiation is simply shielding matter: a bulkier spacecraft. However, this chungus-vessel would be prohibitively heavy and expensive to launch. Another option is to use materials that shade more effectively without weighing more. These materials do not currently exist. Other ideas, such as force fields or drugs that counteract the effects of radiation, remain in the distant realm of theory. Right now, there is no way to get to Mars or beyond without exposing astronauts to potentially lethal doses of radiation.
It would be almost poetic if the limitations that ultimately keep us grounded were not distance and time, but the limitations of our bodies themselves. But it makes sense. We have evolved for billions of years to live hereand only here: so much gravity, so much exposure to radiation, this temperature and pressure and composition of the atmosphere. When talking about Goldilocks’ habitable zone, there’s nothing special about these parameters – they’re just what humans are designed for.
This is not necessarily a death sentence for space exploration and colonization; the same sci-fi brain that can imagine colonizing other planets can easily imagine, I don’t know, genetic engineering to protect our kidneys from the ravages of space. But there are a lot of very smart people who believe that these and other problems are truly insurmountable, that we will never live on other worlds. They could be right! My first reaction is that I find it daunting, but maybe it doesn’t have to be. Maybe instead it might be galvanizing to know that we as a species have to live and die here. There’s no shame in that – it’s the case for every other species so far – and maybe it’s motivation to make the best of what we’ve got, to preserve it, to stop screwing it up. If there is no escape from an uninhabitable Earth, the only option is to fix it.