Outdoor travel will almost certainly cause cancer in astronauts

When Elon Musk unveiled SpaceX's plans to send humans to Mars in September 2016, he had a remarkably cavalier attitude to the dangers of space radiation.

"There is going to be a risk of radiation, but it is not deadly," he told the audience in Guadalajara, Mexico. "There will be a slightly increased risk of cancer, but I think it is relatively minor, we often talk about radiation, but I do not think it's a big problem."

This is not true, as NASA has pointed out many times. The study after study demonstrates a legitimate increase in mortality and morbidity rates due to prolonged exposure to furious radiation in space.

New discoveries published in the journal Proceedings of the National Academy of Sciences illustrate the destructive effects of spatial radiation on gastrointestinal tissues, disrupting normal physiological functions. Although the results are hardly surprising – radiation of any kind, from space or elsewhere, is harmful to health – they underline how much we do not know the specific consequences of these cosmic dangers. long missions in the deep space.

"[The] The GI tract is important for the nutrition and health of astronauts during space missions, especially for long-duration missions, "said Kamal Datta, associate professor at the Lombardi Comprehensive Cancer Center at Georgetown University. "This is the first such study on intestinal cell migration and further studies will be needed to develop drugs or other technological protective measures to reduce the risk of astronauts."

Spatial radiation can take different forms, but a form of great concern is called galactic cosmic radiation, or GCR, which comes from outside the solar system and includes high-energy particles that penetrate into deep space . The more time you spend traveling in the deep space – for example, during a six-month trip to the Red Planet to start a new life – the more you are exposed to RGC, the more likely you are to develop health. down the road.

The GCR is not really a major problem for current and past astronauts: the Earth's magnetic field is a critical barrier against cosmic rays flooding the planet or any object in low Earth orbit (including the International Space Station). Apollo 17, which lasted only 12 days, was spent by astronauts in deep space.

But there is a big question about what kind of damage a long trip to Mars or elsewhere could cause to a future astronaut body. In this investigation, Datta and his colleagues focused on the effects of heavy ion radiation in the gastrointestinal tract. The radiation of heavy ions is much larger in mass than other components of space radiation, such as X-rays and gamma rays, and our current protection against spaceflight is extremely limited to protect us from these particles. Meanwhile, the gastrointestinal tissue is remarkable for its rapid self-renewal, with the upper layers of cells replacing every three to five days facilitating a continuous migration of new cells upwards. This rapid replacement helps maintain the proper functioning of gastrointestinal functions and absorb nutrients. Astronauts can not afford to suffer from gastrointestinal problems during a space flight of several months.

The Georgetown team exposed a set of 10 identical mice to a "low" ionic radiation dose likely to be present in the interplanetary space, using the NASA Spatial Radiation Laboratory instruments at the Brookhaven National Laboratory, at Long Island. The team examined these mice up to one year after radiation exposure and found that their GI cells could not absorb nutrients or healthy or gamma-exposed mice, due to disturbances in the replacement of the tissue layer. Iron-irradiated mice also developed tumor polyps in the gastrointestinal tract, and even suffered DNA damage that caused increased damage and disruption to cell migration required to replace the intestinal mucosa. .

All of this sounds ominous – but there are some important caveats about this study. Mice and humans share much of the same biology, but they remain different organisms, and what happens to one species when exposed to radiation will not necessarily occur on the other. "In the absence of human data," said Datta, "it's the best approach we can take."

According to Jeff Chancellor, a nuclear physicist at Texas A & M University who was not involved in the study and has already written about the barriers to studying space radiation, the "low dose" used by researchers is about 150 times higher than what astronauts flying in interplanetary space would be exposed to. "They received the equivalent of about an estimated dose exposure of about one to two years, and this in just a few minutes," he told the Daily Beast. "Basically, you take a shotgun on all those cells and you just destroy them. You do not tolerate any regenerative effect, nor any natural adaptation of the body. You just suppose the worst. "

In addition, the RAG "encompasses almost all the ions of the periodic table," he said. "You have approximately, at one point, 20 to 30 ions at hundreds of different energies imposing on a human subject in space", which is a radically different environment than the single beam of light. heavy ions exposed to mice in this study.

"There is spatial radiation," he said, "and then there is an operationally relevant space radiation environment." These are two different environments and the study of the biological transformation of man by the first do not help us.

These problems are not necessarily against the researchers; the researchers seem to have conducted the best kind of study they could do. "As far as I know, it's a beautiful study," said the Chancellor. "It's methodical, with a very solid scientific methodology.

"But," he stressed, "we are simply limited in how to simulate the environment as it affects human biology."

It would be extremely helpful to send humans into space aboard a rocket whose launch costs hundreds of millions of dollars, to let the radiations overwhelm them and take notes. But we obviously can not do that. Instead, we are relegated to the use of animal models, exposing them to punctual radiation episodes rather than at an ever slow and natural pace. The findings of the study point to something new about how space radiation could affect humans en route to Mars, but they also inadvertently highlight why we should exploit this new information with a grain salt.

For his part, the Chancellor tries to remedy these limitations and corrects, he says, a recent increase in the number of studies of this type making more and more demands. He is currently publishing a new article in the peer-review that describes a new model to more accurately reproduce on the ground the spatial radiation environment that would affect astronauts during different types of missions.

And recently, said Datta, "NSRL has also made available low-dose chronic exposures over a month for a better approximation of space radiation during deep-space missions.

The ultimate hope is that better emulation of space radiation can help us develop solutions that protect us. After nearly sixty years of manned spaceflight, we still have no magic armor or miracle drug pill to counter the effects of space radiation and preserve the safety of our guts. But we are getting closer.