No matter how much you like your crewmates, a three-year mission to Mars would test the even the best of relationships.
And that's not even the primary reason why future long-duration space travelers may spend part of the journey in suspended animation.
There's the tremendous expense of carrying food, oxygen and carbon dioxide scrubbers to keep astronauts alive, not to mention the hassle of processing their urine and feces.
"Wouldn't it be neat if you could just put them out?" said Warren Zapol, the head of anesthesiology at Harvard University's Massachusetts General Hospital.
One option would be to cool the crew cabin into a big chill. But body temperatures below 30 Celsius (86 degrees F) can disturb the heart's rhythm. Another possibility would be to have the astronauts breathe swamp gas.
Zapol and colleagues report in this month's Anesthesiology journal about how hydrogen sulfide -- the same stuff produced by rotten eggs and swamp gas -- slows mouse metabolism without cutting blood flow to the brain.
"The mice aren't asleep," Zapol told Discovery News. "If you pinch their tails, they respond.
"I don't know what it's like," he added, "probably some slow-motion world."
There are many questions and years of research before healthy people like astronauts would be put into hibernated states, but the procedure could find an earlier application in cases of traumatic injury when life itself is at risk.
"Sixty percent of people in war are dead right there on the field," Zapol said. "They are instantly hurt, and because there is no blood and no fluids in the field, by the time they get to a hospital they are cold and dead and there is nothing to fix.
"During this early period after trauma, if we could freeze you down or shut you down, we could restart you after we fix the aorta, or whatever has been damaged," Zapol said.
Emergency medical workers have tried cooling victims, but the amount of cold water needed to reach effective temperatures makes the technique impractical, particularly in battlefield situations.
"Corpsmen aren't walking around with 150 pounds of cold water," Zapol said. "But what if you could just fog them with hydrogen sulfide?"
During Zapol's experiment, metabolic measurements of the mice, such as their consumption of oxygen and production of carbon dioxide, dropped as early as 10 minutes after they began inhaling hydrogen sulfide.
They remained low as long as the gas was administered. The mice returned to normal within 30 minutes after normal air started to flow.
The animals' heart rate dropped nearly 50 percent while they were breathing the gas, with no significant change in blood pressure or the strength of the heart beat. Respiration rates decreased, but there were no changes in blood oxygen levels, suggesting that vital organs were not at risk of oxygen starvation, the researchers report.
Zapol plans additional experiments on larger mammals, probably sheep.
"Before you use it on astronauts, you want to make sure it's very, very safe," he said.
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