[The Living Body
Luther Lazaro
Think of what you need to survive, really just survive. Food? Water? Air? Facebook? Naturally, I'm going to concentrate on water here. Water is of major importance to all living things; in some organisms, up to 90% of their body weight comes from water. Up to 60% of the human adult body is water.
Each day humans must consume a certain amount of water to survive. Of course, this varies according to age and gender, and also by where someone lives. Generally, an adult male needs about 3 liters (3.2 quarts) per day while an adult female needs about 2.2 liters (2.3 quarts) per day. All of the water a person needs does not have to come from drinking liquids, as some of this water is contained in the food we eat.
According to Dr. Jeffrey Utz, Neuroscience, pediatrics, Allegheny University, different people have different percentages of their bodies made up of water. Babies have the most, being born at about 78%. By one year of age, that amount drops to about 65%. In adult men, about 60% of their bodies are water. However, fat tissue does not have as much water as lean tissue. In adult women, fat makes up more of the body than men, so they have about 55% of their bodies made of water. Thus:
There just wouldn't be any you, me, or Fido the dog without the existence of an ample liquid water supply on Earth. The unique qualities and properties of water are what make it so important and basic to life. The cells in our bodies are full of water. The excellent ability of water to dissolve so many substances allows our cells to use valuable nutrients, minerals, and chemicals in biological processes.
Water's "stickiness" (from surface tension) plays a part in our body's ability to transport these materials all through ourselves. The carbohydrates and proteins that our bodies use as food are metabolized and transported by water in the bloodstream. No less important is the ability of water to transport waste material out of our bodies.
NASA engineers use the lessons learned to better design spacecraft and improve the fit and functions of spacesuits. The research also aids in the development and assessment of medical standards, physical fitness programs and standards, physiological and psychological adaptation training, sensorimotor training, and nutritional health protocols.
Understanding the effects of spaceflight on humans is essential as astronauts move from the International Space Station in low-Earth orbit to deep space destinations on and around the Moon, and beyond. With the Artemis program, NASA will land the first woman and next man on the Moon using innovative technologies to explore more of the lunar surface than ever before, gathering new data while keeping astronauts healthy and safe.
NASA is particularly interested in investigating how the body reacts to long-duration spaceflight as the agency plans for extended missions on the Moon and Mars. Scott Kelly and Christina Koch were the first American astronauts to spend nearly one year in space onboard the space station, twice the previous average. Scott, Christina, and seven other astronauts have spent more than 200 days in space during a single spaceflight.
In addition to spending almost a year in space, Scott was involved in the unique Twins Study. Scott participated in several biomedical studies onboard the space station while his identical twin brother, retired astronaut Mark Kelly, stayed on Earth as a control subject, someone who provides a basis of comparison.
The study provided valuable data about what happened to Scott, physiologically and psychologically, as compared to his brother Mark. Their contribution to science helped generate data that researchers will use for decades to come.
NASA is planning more dedicated extended-duration research on the space station. The studies are expected to shed light on how the body adapts to living in the spaceflight environment for various longer time periods, which will be pivotal for future deep space missions.
What exactly happens to the body in space and what are the risks? Are the risks the same for astronauts who spend six months on the space station versus those who may be away on a Mars mission for years?
A big challenge in reducing the risks of radiation exposure is that some space radiation particles (especially galactic cosmic rays) are difficult to shield against. Exposure to increased radiation can be associated with both short- and long-term health consequences, depending on how much total radiation astronauts experience and the time frame in which they experience that exposure.
Increased risk of cancer and degenerative diseases, such as heart disease and cataracts, have been observed in human populations exposed to radiation on Earth. Health risks for astronauts from radiation exposure in space are mainly driven by long-term impacts.
Additionally, animal and cellular research indicate that the type of radiation in the space environment has a larger impact on health outcomes compared to the radiation experienced on Earth. Not only will astronauts be exposed to more radiation in space than on Earth, but the radiation they are exposed to could pose increased risks.
The Key: The current strategy to reduce the health risks of space radiation exposure is to implement shielding, radiation monitoring, and specific operational procedures. Compared to typical six-month space station missions, later Moon and Mars missions will be much longer on average. Consequently, the total amount of radiation experienced and associated health risks may increase.
NASA is developing new radiation detectors to monitor and characterize the radiation environment, which will provide better estimates of the dose and type of radiation to which the crews are exposed. Scientists and engineers are optimizing and implementing operational procedures that use available vehicle stowage and materials to reduce radiation exposure effectively.
To investigate the health risks of space radiation exposure beyond low-Earth orbit, NASA supports research that analyzes the biological effects of simulated cosmic rays at ground-based research facilities. Research at these facilities helps NASA understand and reduce the risk of space radiation, ensure proper measurement of the doses that astronauts receive on the space station and in future spacecraft, and develop advanced materials that improve radiation shielding for future missions.
Expedition crews selected for a stay onboard the space station are carefully chosen, trained, and supported to ensure they will be able to work effectively as a team for the duration of their six to 12-month missions. Crews for a Moon or Mars mission will undergo even more careful assessment, selection, and preparation since they will travel farther and potentially for longer than previous humans in an isolated and confined environment, with only a few other people. Additionally, crews will likely be international and multi-cultural, making cross-cultural sensitivity and team dynamics paramount to mission success.
Ensuring astronauts get quality sleep is also important; otherwise, their internal biological clocks, or circadian rhythm, might be altered by factors like different dark and light cycles, a small and noisy environment, the stress of prolonged isolation and confinement, and a 37-minute extended day on Mars.
It is important to prepare for the fatigue astronauts may experience during spaceflight, given that there will be times with heavy workloads and shifting schedules. To prevent crew boredom, NASA considers the kinds of activities in which the astronauts will participate during a multi-year round trip to Mars.
Communication and understanding among crew members are vital to the success of the mission, and changes in morale and motivation are possible as the mission unfolds. This may relate to reduced stimulation, the longing for loved ones, or feeling unable to assist with family emergencies back on Earth, regardless of how long the mission lasts.
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