Astronaut Scott Kelly, who spent 340 days aboard the International Space Station, said that being in space appears to have "permanent" effects that aren't fully understood.
“The environment astronauts are exposed to while in space is unlike anything we experience here on earth. Specifically, astronauts are exposed to high levels of radiation and carbon monoxide, and a micro-gravity environment which causes loss of bone and muscle, vision impairment and effects on our immune system to name a just a few,” he wrote in his prepared remarks to the House Science, Space and Technology committee. “These are very real issues that need to be solved before the human race is able to reach destinations beyond the Earth and the Moon.”
"Exposure to the space environment has permanent effects we simply do not fully understand," he added.To read more, click here.