A new study has found that areas of the brain containing fluid expand when astronauts are on space missions for six months or longer. The American space agency NASA funded the study. The brain areas are called cerebral ventricles. They contain cerebrospinal fluid, a clear and watery liquid that flows in and around the brain and spinal cord. The fluid helps protect the brain against sudden impact. The fluid also removes waste products. Researchers based their research on brain scans of 30 astronauts. They found that it took three years for the ventricles to fully return to normal size after long space missions. The results mean that astronauts may need to wait at least three years between longer space missions.

一项新研究发现，当宇航员执行六个月或更长时间的太空任务时，大脑中含有液体的区域会扩大。 美国航天局 NASA 资助了这项研究。大脑区域称为脑室。 它们含有脑脊液，一种透明的水状液体，在大脑和脊髓内部和周围流动。 这种液体有助于保护大脑免受突然的冲击。 该流体还可以去除废物。研究人员的研究基于 30 名宇航员的脑部扫描。 他们发现，经过长时间的太空任务，心室需要三年时间才能完全恢复正常大小。 结果意味着宇航员可能需要在较长的太空任务之间等待至少三年。

Heather McGregor is a University of Florida brain scientist. She was the lead writer of the study, which appeared in the publication Scientific Reports. She told the Reuters news agency that if the ventricles do not have enough time to get back to normal size, they could have less space to expand on a following trip to space. This could affect the brain’s ability to deal with the changes in gravity that astronauts face. Rachael Seidler is a University of Florida professor of applied physiology and kinesiology. She was also a writer of the study. She said, “the impact of ventricular expansion is currently not known,” and that scientists need to do more studies on the subject. She added that the expansion likely compresses the area of the brain around the spaces. To compress means to press, squeeze or make smaller. On Earth, valves in the body’s vascular system prevent fluid from staying at our feet due to gravity. But in space, without gravity, the valves push the fluid more towards the head. Seidler said this is what likely causes the ventricular expansion. As a result, the brain sits higher in the skull.

希瑟·麦格雷戈是佛罗里达大学的脑科学家。 她是这项研究的主要作者，该研究发表在《科学报告》杂志上。 她告诉路透社，如果心室没有足够的时间恢复到正常大小，那么在接下来的太空旅行中，它们的扩张空间可能会更少。 这可能会影响大脑处理宇航员面临的重力变化的能力。雷切尔·塞德勒（Rachael Seidler）是佛罗里达大学应用生理学和运动机能学教授。 她也是该研究的作者。 她说，“目前尚不清楚心室扩张的影响”，科学家需要对此进行更多研究。她补充说，这种扩张可能会压缩这些空间周围的大脑区域。 压缩意味着挤压或变小。在地球上，人体血管系统中的阀门可防止液体因重力而停留在我们的脚下。 但在太空中，没有重力，阀门将流体推向头部。 塞德勒说这可能是导致心室扩张的原因。 结果，大脑在头骨中的位置更高。

The study involved 23 male and seven female astronauts from the U.S., Canadian and European space agencies. The average age of the astronauts was 47. Eight of the astronauts traveled on space shuttle missions that lasted about two weeks. Eighteen were on International Space Station (ISS) missions of about six months. The other four took part in ISS missions that lasted about a year.The astronauts who went on short missions experienced little or no ventricular size change. A size increase occurred in astronauts after missions of six months or longer. There was no difference in those who went on missions for six months compared to those who went on year-long missions. The fact that enlargement did not worsen after six months could be good news for future Mars missions. Astronauts may spend two years in microgravity during trips to Mars. The study results are also good news for people thinking about going on short space tourism flights, Seidler added.

这项研究涉及来自美国、加拿大和欧洲航天局的 23 名男性宇航员和 7 名女性宇航员。 宇航员的平均年龄为 47 岁。其中八名宇航员执行了持续约两周的航天飞机任务。 其中 18 人执行了为期约六个月的国际空间站 (ISS) 任务。 其他四人参加了持续大约一年的国际空间站任务。执行短期任务的宇航员的心室大小变化很小或没有变化。 在执行六个月或更长时间的任务后，宇航员的体型会增加。 那些执行六个月任务的人与执行一年任务的人没有区别。六个月后扩大并没有恶化，这对未来的火星任务来说可能是个好消息。 宇航员在前往火星期间可能会在微重力环境中度过两年。 塞德勒补充说，这项研究结果对于考虑进行短途太空旅游飞行的人们来说也是个好消息。

Low gravity causes other changes in the human body, as well. These include decreases in bone and muscle mass, some changes to the heart and lung system, and issues with the balance system in the inner ear. Longer space missions might also increase cancer risk because of greater exposure to solar radiation.

低重力也会引起人体的其他变化。 这些包括骨骼和肌肉质量的减少，心脏和肺系统的一些变化，以及内耳平衡系统的问题。由于更多地暴露在太阳辐射下，更长的太空任务也可能会增加患癌症的风险。