The loss of bone mass is not nearly the problem it used to be in weightlessness because of improved exercise equipment and procedures, she said. The newest concern is impaired vision related to pressure on the brain and spinal cord; in some cases, astronauts suffer vision problems long after their flight.
In a chart held up by the director of Russia's piloted space program, Alexey Krasnov, nearly half the slots were red, indicating medical risks to eventual trips to the moon, asteroids and Mars.
"There are many things we don't know," Krasnov said. "We should take some risks upon ourselves" now before embarking on such ambitious endeavors beyond Earth's orbit.