Shuttle's Human Experiments Pave Way for Moon, Mars Voyages

John Roach
for National Geographic News
July 17, 2006
The space shuttle Discovery successfully finished its latest voyage today, touching down at Cape Canaveral, Florida, at 9:14 a.m. local time.

But science experiments started during the 13-day mission will continue.

(See photos of Discovery's latest mission highlights.)

Throughout their nearly two weeks in space, the crew kept diaries of their sleeping habits and filled containers with various bodily fluids.

The tasks were part of experiments designed to help better prepare astronauts to stay healthy during long-distance space flights to the moon and Mars.

(Read "NASA Aims for Moon by 2018, Unveils New Ship.")

"We want them to be in the best shape possible," said Daniel Feeback, a Discovery mission scientist and director of the Muscle Research Laboratory at the NASA Johnson Space Center in Houston, Texas.

Feeback's lab is part of the center's Human Adaptations and Countermeasures Division, which studies the effects of spaceflight on human health.

Low Gravity

Specifically, researchers hope to learn more about the effects of radiation exposure on the human body; how spaceflight affects the immune system; and whether spaceflight can reawaken viruses, such as herpes, that can lie dormant.

In one experiment during the July Discovery mission, astronauts wore wristwatches that monitored their round-the-clock activity and patterns of light-exposure.

The data, combined with daily journal entries on sleep quality, should help scientists design drugs and sleeping arrangements that keep astronauts well-rested and alert.

Other experiments were designed to examine blood, urine, and saliva samples taken before, during, and after the mission.

Feeback says protecting astronauts from cosmic and solar radiation is the biggest threat scientists must overcome to ensure crew safety during long-duration spaceflights.

"Radiation damage can cause lots of problems," he said, noting that it can impair astronauts' cognitive ability, damage their immune systems, and increase the risk of cancer.

(Related online feature: Exploring Space in National Geographic magazine.)

Jeanne Becker is the associate director of the National Space Biomedical Research Institute in Houston, a consortium funded by NASA to study the effects of spaceflight on human health.

She says the zero gravity of space is so foreign to the human body that health issues are certain to arise.

"The body is an amazing machine, absolutely. But we all developed in a one-G environment," she said, referring to the scientific term for the force of gravity on Earth.

"So when we go up and expose our body to almost zero gravity, there are changes in some physiological systems."

In the case of pedestrians on Earth, gravity pulls heavily on the lower body. But in space, astronauts float, using their arms more and their legs less.

Becker notes that with less gravity pulling on astronauts' lower extremities, fluid shifts and pools toward the upward region of their bodies.

"These are really big changes the [body] is adapting to," Becker said.

Bone-loss also accompanies this gravitational "unloading" on the lower body. As a result, Becker noted, "there are increasing levels of calcium present that can sometimes result in increasing [kidney] stone risk."

Astronauts now routinely exercise in space to counteract the bone and muscle loss experienced in spaceflight.

But whether room for such equipment will be available on next generation spacecraft is an open question, Feeback says.

"We may have to have an engineering solution rather than a physical solution," he said.

Astronauts, for example, may have to accept a certain amount of bone and muscle loss during a flight to Mars.

But when they reach the red planet, they might don a spacesuit with built-in artificial muscles to complete mission objectives, such as building a structure.

Feeback says long-duration space missions may also require NASA managers to select flight crews based on their brawn as much as their brains.

"No one really likes to talk about it—we want the brightest—but sometimes the brightest aren't the most athletic," he said.

Emotional Health

Becker says scientists are also paying close attention to the effect of spaceflight on mental health.

"Imagine going on a Mars mission where you're going to be out of touch from friends and family for a very long period of time. These are very real factors that affect emotional well-being," she said.

The sleep research from the latest Discovery mission should address some of these issues, Becker says. Unusual sleep patterns are a common sign of emotional stress.

A host of other Earth-based experiments have been designed to simulate the emotional challenges astronauts face in space.

For example, a NASA Extreme Environment Mission Operations experiment put several aquanauts in a tight-quartered underwater habitat and forced them to work together to solve problems.

Understanding how the aquanauts work in isolated underwater environments allows scientists to prepare astronauts for working together in space, Becker says.

"We need to have good working dynamics among the crew," she said.

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