A trip to Mars could be one of humanity’s greatest achievements, but the journey may carry a hidden danger that threatens astronauts long after they return home. Scientists warn that exposure to deep space radiation could cause lasting damage to the human heart, raising new concerns about the health risks of sending people to the Red Planet. With future missions to Mars expected to keep astronauts away from Earth for months or even years, could the trip permanently weaken their hearts? Read on to learn what the researchers found and why it could change the way we prepare for human exploration of Mars. Deep space radiation can leave lasting scars on the heart Traveling beyond Earth’s protective environment exposes astronauts to two major dangers: cosmic radiation and microgravity, the condition in which people experience apparent weightlessness. Although scientists know that both can affect human health, the long-term consequences remain unclear. A study by researchers at the Medical College of Wisconsin, published in PLOS One, investigated how these conditions might affect the body over time. The findings suggest that deep space radiation can cause progressive damage to the heart, weaken immune defenses and trigger genetic changes associated with serious cardiovascular problems. How scientists simulated a trip to Mars Because researchers cannot yet conduct long-term experiments in deep space, they must recreate important aspects of the environment on Earth. Testing long-term radiation exposure in humans would also not be practical or ethical, so the team used rats to investigate the potential risks. To simulate weightlessness, the researchers used a technique developed by NASA called hindlimb unloading. Middle-aged male rats had their hind legs suspended at a 30-degree angle for 30 days. This shifted bodily fluids toward their heads and reduced the weight placed on their lower bodies, approaching certain effects of microgravity. The team recreated the cosmic radiation at NASA’s Space Radiation Laboratory at Brookhaven National Laboratory. Using a specialized simulator called simGCRsim, the researchers exposed the animals to high-energy particles, including protons and heavier ions such as silicon and iron. Similar particles can pass through the shielding of spacecraft during deep space missions. The rats spent five days in the weightlessness simulation before receiving a brief, intense radiation exposure. They were then suspended for another 25 days. The researchers monitored them for about a year, allowing them to examine delayed effects. The heart damage continued to worsen after radiation exposure. One of the study’s most concerning findings involved perivascular fibrosis, a condition in which scar tissue develops around blood vessels. In the heart, this tissue can interfere with the vessels that supply blood to the heart muscle. Rats exposed to a radiation dose of 1.5 gray, a unit that measures absorbed radiation, developed these types of scars. 270 days after exposure, the amount of scar tissue had doubled, potentially restricting blood flow and increasing the risk of a heart attack. Simulated weightlessness did not appear to contribute significantly to this particular result. Radiation was the main factor associated with the damage. Even the lowest radiation dose, intended to approximate the cumulative exposure of a three-year mission to Mars, produced worrying results. Although scarring on the heart was not immediately evident, 83% of the rats developed it within a year. This raises concerns that radiation-related cardiovascular damage could emerge years or decades after astronauts return to Earth. However, the findings in rats do not establish that humans would experience the same effects or the same timeline. Radiation also weakened immune defenses. The researchers found that radiation exposure had lasting consequences for the animals’ immune systems. Months after the experiment, their spleens had lost about two-thirds of their natural killer (NK) cells. These immune cells help destroy virus-infected cells and abnormal cells, including some cancer cells. A substantial decrease in their numbers could weaken the body’s ability to defend itself against disease. Microgravity alone did not produce the same lasting effect. Rats exposed to simulated weightlessness eventually recovered normal cellular levels, but recovery was more limited when radiation was also involved. The researchers suggested that cosmic radiation could interfere with the bone marrow’s ability to respond to physiological stress. The bone marrow produces blood cells, including many of the cells essential for immune function. The genetic changes raised further cardiovascular concerns. Another worrying discovery emerged when scientists examined the white blood cells of rats. At 235 days after radiation exposure, they identified persistent mutations in several genes associated with clonal hematopoiesis of undetermined potential (CHIP). CHIP occurs when blood cells acquire mutations that allow them to multiply more successfully than other cells. Although it becomes more common with age, it is associated with an increased risk of blood cancer, heart attacks and strokes. The findings suggest that radiation could accelerate biological changes related to aging and cardiovascular disease. However, the experiment cannot establish how these mutations would affect astronauts throughout their lives. More research is needed before human missions to Mars. The study has important limitations. The researchers administered the radiation in a single, intense exposure rather than spreading it over months or years of an actual space mission. It remains uncertain whether the body’s repair mechanisms would respond differently to prolonged exposure. The experiment also involved only male rats, meaning the results may not reflect how females or humans would respond. However, the findings highlight a major challenge for future Mars exploration. Protecting astronauts from radiation will require more than ensuring their immediate survival during a mission. Scientists also need to understand and reduce health risks that could develop long after their return. Source: Universe Today
