Humankind has dreamed of conquering outer space, but while we have successfully sent astronauts beyond the earth's atmosphere, human bodies apparently remain unfit for space travel.
Ten years ago, scientists were concerned with astronauts returning to Earth with weaker bones. The body does not support its weight in space so it begins dismantling bone tissues at a fast rate than on earth, causing a reduction in bone density by up to 2 percent each month. Improved exercises and osteoporosis drugs, however, now allow astronauts to come back with almost as much bone as they had before they left.
Still, there are plenty of health-related hurdles when sending people for spaceflight. The human body is about 60 percent water and this poses a problem in free falling space. Fluid moves more easily from one part of the body to another and this results in leg atrophy, puffed faces and increased pressure inside the skull.
"Your head actually feels bloated," said Mark Kelly, a retired NASA astronaut who has flown on four space shuttle missions, told the New York Times. "It kind of feels like you would feel if you hung upside down for a couple of minutes."
One major concern is radiation. Astronauts receive major doses of radiation outside the Earth's protective magnetic field and atmosphere, raising their risk of dying from cancer.
A study conducted by scientists at the Brookhaven National Laboratory on Long Island suggests that space radiation can cause brain damage. The researchers bombarded mice with radiation that mimics the high-energy cosmic rays in outer space. They found that the mice took longer to navigate a maze suggesting that the radiation had a negative effect on their brain. Scientists say other parts of the body, including the heart, nervous system and digestive system, are at risk of damage.
Vision is also a problem. During their six-month long stay on the International Space Station in 2009, Michael Barratt and Robert Thirsk, who are both astronauts and doctors, noticed they had difficulty seeing things up close and later confirmed with an eye exam that their vision shifted to farsightedness. Many astronauts reportedly complained of vision changes after spaceflight, but those changes only recently began to be studied.
Scientists at the Johnson Space Center, NASA's center for human spaceflight program, now have until the 2030s to work on these problems ahead of a manned mission to Mars.
John B. Charles, chief of the international science office of NASA's human research program, said he believed NASA could already send astronauts to Mars and bring them back alive, but noted that it is crucial they arrive productive and in good health.
"My goal," Charles said, "is to see a program that doesn't deliver an astronaut limping to Mars."
