Wednesday, December 7, 2011
Boning Up in Space
JAXA astronaut Koichi Wakata in the Destiny laboratory of the International Space Station in May 2009. Image source: NASA.
Some space advocates think human spaceflight means exploration, and exploration only. It's not hard to find on space-related web sites comments posted by those who demean the International Space Station. They believe that the government space program's sole purpose should be going to the Moon. Others view the Moon as trivial; they want to go to Mars NOW!
These folks conveniently overlook one basic fact — the human body was not designed for long-duration spaceflight.
A week-long round-trip to the Moon? No big deal.
But as the weeks and months add up, bad things start to happen to the human body.
Astronauts and cosmonauts serve a six-month tour of duty on the ISS. Studies are starting to emerge which show that long-duration flight could badly debilitate star voyagers, suggesting they might not be physically capable of walking on Mars, much less surviving the voyage.
A report issued in September by the National Academies found that long-duration space flight may be causing headaches and blurry vision among some astronauts. According to the Orlando Sentinel:
The affliction, known as papilledema, is a swelling of the optic disk and can cause blurred vision, blind spots or — in severe cases — loss of vision. It was found in nearly half — seven of 15 — astronauts examined in one study by NASA.
This included "some lingering substantial effects on vision," and astronauts were "not always able to re-qualify for subsequent flights," according to the 102-page report, which provided no additional details.
An October NASA report raised concerns about the atrophy of the human heart:
Atrophy (decrease in size) of the heart muscle appears to develop during space flight and its ground-based analogues (bedrest) which could lead to impaired functioning of the heart and fainting upon return to gravity on the Earth, the Moon, or Mars. It also may be related to heart rhythm abnormalities that have been recorded in crewmembers on prior missions.
And now evidence is beginning to emerge of a disturbing rate of bone loss while in microgravity.
According to Dr. Toshio Matsumoto of the Japan Aerospace Exploration Agency (JAXA):
... [I]n the microgravity environment of space, bone metabolism becomes unbalanced and bone mass is reduced very rapidly. When we measured the bone density of astronauts who stayed in space for a long period, the results showed that femur density was reduced on average by 1.0% to 1.5% a month. This is a drastic reduction - this level of loss normally takes more than a year in a patient with osteoporosis. At the same time, when bone mass is reduced, calcium dissolved from bones into urine can cause urinary lithiasis, or kidney stones. Astronauts on the space station exercise for two hours a day, but to provoke bone formation, strong instantaneous impact is needed. Thus, even a wide range of exercises in zero gravity cannot prevent the rapid loss of bone mass.
JAXA is studying whether oral administration of bisphosphonates, a drug used on Earth to combat osteoporosis, may help in space.
JAXA astronaut Koichi Wakata and other astronauts have participated in bisphosphonate experiments while aboard the ISS. Wakata flew aboard the ISS from March through July 2009. The results of his experiment are being analyzed by Dr. Matsumoto. Other astronauts may participate in the experiment. Wakata is scheduled to return to the ISS in late 2013, and will become the first Japanese commander of the space station.
Former Defense Secretary Donald Rumsfeld once famously said, "There are things we do not know we don't know." That sentiment applies to long-duration spaceflight.
Before we commit to a permanent lunar colony, to a round-trip flight to an asteroid, or an expedition to Mars, we still have much to learn about the long-term effect of microgravity on the human body.
And that's one reason why the ISS is so critical to the future of humanity.