A study published in Science Advances has found that Mars lacks enough gravity to keep astronauts healthy in microgravity. The researchers exposed mice to various levels of artificial gravity, including 0.67 g (67% of Earth's gravity), found that this was a key threshold for muscle atrophy. The study also found that even a low gravity level was enough to stop the muscles from deteriorating completely, although the rodents’ muscle fibers did change in composition. The results may not directly transfer to humans, but they are a warning sign that gravity levels on the Moon and Mars likely aren't sufficient for preventing atrophy over extended periods of time. The understanding of this threshold could help scientists establish a sustained presence on the moon and Mars.