A study published in PLoS One shows that the human heart may not survive a trip to Mars. Researchers found that radiation and weightlessness cause dangerous scarring around coronary vessels. These conditions also weakened the immune system, making it harder for the body to fight off viruses and potential cancer.
Mars is not an ideal environment for humans, but the journey to the Red Planet itself will devastate the human body even before astronauts land on its surface. A study has found that our hearts will not be able to survive the trip.
An experiment on the effects of space environment on human body has thrown up a lot of bad news that can whitewash plans to conquer Mars and beyond. The study done by researchers from the Medical College of Wisconsin, and published in PLoS One, shows that radiation and weightlessness can destroy the human heart and increase the chances of developing cancer.
NASA developed a protocol called hindlimb unloading (HLU) to simulate weightlessness in rats. A harness was used to lift their back legs off the ground at a 30 degree angle for thirty days. This led to much of the fluids in the body rushing towards their heads, taking off the weight off their lower bodies. This is as close as they could come to mimicking astronauts in microgravity.
To recreate radiation on Earth, they utilised the NASA Space Radiation Laboratory at Brookhaven National Laboratory. This lab can simulate the radiation environment as it is outside the Earth's atmosphere.
The rats were "unloaded" for five days and hit with extreme high radiation levels for a few minutes. They remained suspended for 25 more days. The harness was then removed and the rats for monitored for a year, which is equal to nearly 25 human years.
The study focussed on how the simulation affected their hearts. Scientists found that 1.5 Gray of absorbed radiation led the rats to develop perivascular fibrosis, a type of scar tissue around the coronary vessels that feed blood to the heart. This scar doubled in 270 days, squeezing the blood vessels and increasing the chances of heart attack. The effect was entirely caused by radiation.
When the rats were exposed to lower radiation, equal to the radiation exposure over the course of a three year mission to Mars, the scarring wasn't visible. However, 83 per cent of the rats developed it after a year. This means that the scarring would take decades to become visible in humans.
Their immune system also took a hit, with their spleens losing two thirds of its Natural Killer (NK) cells that wipe out virus-infected and potentially cancerous cells. This was the result of both microgravity and radiation.
Sequencing of the genomes of their white blood cells showed permanent mutations in a number of genes 235 days after exposure to the radiation. Some of these genes are tied to Clonal Hematopoiesis of Indeterminate Potential (CHIP) which appears as we age because of a single mutated blood cell. This mutated blood cell carries with it an increased risk of leukemia and quadruples the risk of heart attacks and strokes.
Even though the study has its limitations, especially since all the radiation was delivered quickly, it is still bad news for human dream of long-term space flight and reaching the vast expanse of the universe.