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Biological Clocks For Space Travel February 10, 2003 -- President George W. Bush recently set two goals for the nation’s space program: humans will return to the moon by 2020, and land on Mars by 2030. But human biology is not designed for space travel. The earth is, in effect, a spaceship, with an atmosphere, gravity and light cycles that allow us to thrive. Space, however, is inhospitable. To travel across vast distances of space, humans must bring along the conditions of spaceship earth. Researchers at the University of Virginia have begun looking for ways to help the human body adapt to months, perhaps years, of space travel during a Mars mission. Once astronauts leave Earth, there will be no day/night cycles. And on the Martian surface, the days are slightly longer than the 24-hour day on Earth, which likely will skew the natural rhythms of the astronauts’ biological clocks. Without the routine of day and night during space travel, astronauts must create an artificial wake/sleep cycle to override their bodies’ natural clocks, which are set to Earth time cycles. Michael Menaker, U.Va. professor of biology, and colleagues, including Gene Block, U.Va. vice president and provost and professor of biology, are using animal models to explore ways to adapt circadian rhythms to space by manipulating the timing of meals, hormone administration, exercise and light conditions. What they learn may be used to adjust the environments and schedules of astronauts to maximize their performance in space. “We are part of a team that is trying to understand what is likely to happen to circadian organization during prolonged space travel,” Menaker said. “We want to know how to make the circadian system behave normally under abnormal conditions. Even small variations in environmental conditions can cause big problems for biorhythms and for the important cognitive abilities that depend on them.” Astronauts must remain alert while performing complex activities under the unusual physical and environmental conditions of space. To perform well, they need at least six hours of sleep per day, even as their daily activity and rest cycles are altered by both their mission requirements and the loss of the normal day/night cycles on Earth. Once astronauts reach Mars, about 64 to 105 million miles from Earth (it varies, owing to the nature of elliptical orbits), they will have to “synchronize to Mars time,” Menaker said – a day on Mars is nearly 40 minutes longer than an Earth day. The light on Mars also is much redder than the light on Earth, which may affect the astronauts’ biological clocks. Menaker and colleagues are matching the intensity of wavelength differences on their lab specimens to simulate the Martian light conditions. Biological clocks are the body’s internal timekeepers that regulate the functions and behaviors of organs. In recent years, Menaker and his colleagues have shown that a central timer in the brain sends signals to other organs and tissues, regulating the body’s activity/rest cycle. They have demonstrated that mammals have specialized light sensing cells in the eyes that synchronize the clock in the brain to day and night. They also have shown that organs such as the lung and liver contain their own biological clocks, which are regulated by the central timer in the brain. It’s a complex system, but these circadian rhythms help mammals sleep and stay active, controlling energy levels, growth, moods and aging. “Our basic goal is understanding how the multiple oscillators in various organs of which the circadian system is composed are organized and how this organization is maintained,” Menaker said. “These are basic biological questions. Once this is understood, countermeasures can be designed to compensate for the circadian disorganization produced by space travel, and also by ‘jet lag’ and shift work.” A better understanding of biological timing will enable the development of counter-measures, and help astronauts reduce mistakes and accidents due to fatigue. Lack of sleep affects a person’s level of alertness, eating cycles, and can disrupt the metabolism. Sleeplessness also can lead to declining cognitive abilities and possibly a shortened lifespan. These are serious health concerns for the average person and more so for astronauts who must perform at their peak under stressful conditions. Menaker’s space-related research is sponsored by the National Biomedical Research Institute, a NASA-affiliated consortium of 12 institutions working to prevent or solve health problems related to long-duration space travel and prolonged exposure to microgravity. The group’s purpose is to help ensure safe and productive human space flight. Contact: Fariss Samarrai, (434) 924-3778 |
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