Largest compendium of space medicine sheds light on what happens to astronauts’ bodies

In the 2030s, construction of permanent lunar bases is set to begin, and in the following decades, it is possible that astronauts will try to reach Mars. These major projects, in addition to space tourism, will increase the number of people traveling into space. That’s why it is important to have a clear understanding of the health effects of these journeys. Decades of space exploration — particularly the large number of astronauts who have lived on the International Space Station for months — have provided much information about what happens to the body in orbit. On Tuesday, the journal Nature published the Space Omics and Medical Atlas (SOMA): the largest compendium of data on aerospace medicine and biology to date. The authors of the paper suggest that space medicine needs to develop its own databases, tools and protocols to reach the level that the discipline has on Earth.

The SOMA package includes data collected in projects such as the study carried out with the Kelly twins, which measured the differences between the sibling who traveled to space and his twin who remained on Earth, the Inspiration4 project, a three-day excursion for four amateur astronauts organized by SpaceX, and data from the Japanese space agency (JAXA) missions.

Inspiration4 data show that a short-duration flight in low Earth orbit, at just over 500 kilometers altitude, produces changes similar to those of longer duration. Many of these effects are similar to those observed when the body perceives a threat, such as a high level of cytokines, proteins that regulate the response of immune system cells, telomere lengthening, which also happens when there is a need for cell repair, genetic changes that favor immune activation, and responses to DNA damage.

Christopher Mason, a professor at Cornell University and one of the authors of the studies, believes that the disruption observed in the immune system “is part of the adaptation to space flight, to a situation in which the body is subjected to stress by microgravity, by greater exposure to radiation and a strange environment, with fluid changes that disrupt the lymphatic system.” “Our bodies have evolved to live with severity and we believe that these changes in the immune system are an adaptation for an undetermined disorder that the body perceives,” he adds.

The good news is that more than 95% of the markers altered during space flight returned to normal levels in the first three months after returning to Earth. Some cytokines, proteins and genes remained activated during space flight for more than three months. Further study will be needed to determine whether this has negative consequences. Women recovered normal levels of the markers studied faster than men.

Another study, published on Tuesday in Nature Communications, identified a physiological obstacle to a journey as long as the one needed to get to Mars and back. Most space travel, such as the journeys taken by astronauts orbiting the International Space Station (ISS) or space tourists, take place in low Earth orbit, where they are still largely protected from cosmic radiation by the magnetic field of the planet. Only 24 people, Americans who traveled to the Moon with the Apollo program between 1969 and 1972, were exposed to rays without this shield, and none of them were exposed for more than 12 days.

Although space travel has seen bone loss, a weakening of the heart and eyesight, and the development of kidney stones, astronauts have never been exposed to the hostility of deep space for the length of time needed to go to Mars and go back. A team from University College London analyzed what happens in the kidneys when traveling to space, accumulating data from astronauts and simulating long-duration trips in mice and rats.

The results show that microgravity conditions or space radiation change the kidneys of humans and animals. On the one hand, microgravity probably changes some structures of these organs, which alters the way they process salts and facilitates the appearance of kidney stones, a problem associated with space flight. These changes could also be accelerated by exposure to cosmic rays. One of the UCL team’s most alarming results is that when they exposed mice to the equivalent of two and a half years of cosmic radiation, their kidneys suffered permanent damage. “If we don’t develop new ways to protect the kidneys, even if astronauts make it to Mars, they may need dialysis on the way back,” says Keith Siew, the lead author of the study. “We know that kidneys take time to show radiation damage. When they are visible, it will probably be too late to prevent them from failing and could be catastrophic for the mission,” he adds.

The studies also analyze the effects of space travel on a possible pregnancy, damage to the skin, intestinal microbiota or liver function. More information will need to be gathered in order to design protection systems or even pharmacological treatments that protect astronauts from the risks of space travel. Some of these products, such as pills that can help withstand radiation, will have applications on Earth, increasing, for example, the safety margins of the radiotherapy received by people with cancer.

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