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March
28, 2007: The landing site is unknown. The rockets
are still on the drawing board. Some of the astronauts haven't
even been born yet.
 Never
mind all that. NASA's journey to Mars has already begun.
The
first steps are being taken onboard the International Space
Station (ISS). "Astronauts are stationed on the ISS for
six months at a time," says Dr. Clarence Sams, lead scientist
for the ISS Medical Project at NASA's Johnson Space Center
(JSC). "Coincidentally, that's about how long it takes
to travel to Mars. We can't simulate every aspect of a 50
million mile journey to Mars," he says, "but there
are many questions we can answer from low Earth orbit."
Right:
Humans on Mars, an artist's concept. Credit: Pat Rawlings/SAIC
and NASA. [More]
For
example, what happens to food and medicine exposed to six-plus
months of space travel?
Curiously, food kept in orbit seems to lose some of its nutritional
impact. Post-flight tests run on astronauts show that "blood
and urine markers of nutritional status didn't match expected
levels of nutrients in space foods," reports Dr. Scott Smith,
head JSC's Nutritional Biochemistry Laboratory. Furthermore,
researchers at JSC's Pharmacotherapeutics Laboratory noticed
that some medicines returned from orbit had lost their potency.
This
could be a sign of radiation at work: high-speed particles of
space radiation occasionally smash into nutrient or medicine
molecules, perhaps damaging those molecules and preventing them
from functioning properly. So far, though, it's speculation.
Neither the cause of the food and medicine breakdown nor how
much breakdown is occurring is yet known, say the researchers.
"We
may have to come up with a plan for protecting our supplies,"
continues Sams. "How fast do food and medicines degrade?
Are we going to have to put supplies in a radiation-shielded
area for the entire trip?"
To
help answer these questions, an experiment running on the
ISS called Stability of Pharmacotherapeutic and Nutritional
Compounds places three identical sets of food and medicine
on the station. One will be returned to Earth after 6 months,
the second after 12 months, and the third after 18. That way
Scott M. Smith and Lakshmi Putcha, principal investigators
for the project at JSC, can figure out the rate at which the
foods and medicines lose their potency. This information is
important because food and medicines must survive not just
the six-month trip to Mars, but the full 3 years of a Mars
mission. Exposure times might even be longer if mission planners
decide to send cargo capsules filled with stashes of food
and medicine to Mars before the crew leaves Earth.
Above: The International Space Station. [More]
Other
experiments on the ISS examine the bodies of the crew themselves,
requiring them to take blood and saliva samples and sonograms
while aboard the station. "There is already quite a bit
of data from shuttle flights and such, but you must understand,
a lot of the measurements of the past were made pre-flight
and post-flight. [We] need to know what's going on in between,
during the mission," Sams explains.
For
example, it's well known that people lose bone and muscle
mass while in weightlessness. But scientists still don't know
how that loss progresses while an astronaut is in space. Is
there an initial, rapid loss as the body adjusts to being
in space, followed by a plateau? Or is it a steady, relentless
decline? When planning on being away from Earth's gravity
for 3 years or more, these questions become important.
Other
questions -- such as how the body reacts to the partial gravity
of the Moon or Mars -- will have to wait until NASA sends
astronauts back to the Moon in the coming decade. Meanwhile,
says Sams, the ISS is an excellent place to start.
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Author: Patrick Barry | Editor:
Dr. Tony Phillips | Credit: Science@NASA
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