Life Support
  Air, Water, and Nutrition
  Waste Management
  Mental Health
  Suits
  Radiation and Zero-G

Habitat On Mars
  Power
  Structure
  Daily Routine

The Effects of Weightlessness - Major Concerns

Muscular deconditioning and loss of bone marrow:

Due to lack of use in microgravity, the astronauts' skeletal muscles will lose mass, strength, and endurance. After a long duration flight, the muscles will have atrophied so much that an inablity to support the body weight of the astronaut in the presence of gravity will result. In addition to this muscular deconditioning, bone marrow loss can be as high as a 1.5% loss per month in the legs. Although these effects cannot be completely counteracted, their severity can be reduced through preventative measures - a regimented exercise program on a space treadmill to fight muscular atrophy and nutritional supplements to lessen bone marrow loss. 

Fluid shift:

Due to the absence of gravity, blood from the lower body shifts to the upper body. The heart adapts to this by swelling to accomodate the extra flow of blood. The body adjusts to this by reducing the amount of fluid in the body - astronauts take in less fluid while urine flow is increased. The heart returns to its normal size once the amount of fluid is reduced and balanced. The effects of this fluid shift are not particularly dangerous, as the cardiovascular system adapts quickly and effectively. For example, the concentration of red blood cells remains the same, despite the obvious reduction of fluid. This implies that the number of red blood cells in the body is decreasing, an effect known as space anemia. Because the astronauts will have a decreased thirst, it is important to monitor the water intake of the crew; water will help them stay healthy despite the stress of life in space and on Mars. 

Orientation:

In the human body, otolith organs, the inner ear, joints, and touch sensors in the skin detect gravity and keep humans oriented in their surroundings. When weightless in space, however, there is no gravity to stimulate these sensors, resulting in directional disorientation in astronauts. Although the eyes send visual directional signals to the astronaut, the astronaut cannot feel "up" or "down" and therefore has difficulty maneuvering in a weightless environment. To counteract this, each crew member must be trained for weightlessness, and "landmarks" such as handholds and monitors should be placed in the same orientation, in order to provide a non-confusing visual reference. 

Space Radiation

There are two types of space radiation: ionizing and nonionizing. 

Ionizing Radiation

Of the two types of space radiation, only ionizing radiation poses a serious threat to astronauts travelling through space. Its immediate effects include: headache, dizziness, abnormal taste and smell, nausea, vomiting, diarrhea, decreased blood pressure, decreased white blood cells, irritability, and insomnia. Later effects can include: lens opafication, cancer induction, impaired fertility, heritable effects, and developmental abnormalities. The primary sources of ionizing radiation are: Trapped Radiation Belts, Galactic Cosmic Rays (GCR), and Solar Particle Events (SPE).

The level of nonionizing radiation in space may vary over a long term mission from low levels to fatally high levels. In order to shield against these various levels of radiation, including the potentially fatal ones, very heavy metal shielding would be required. However, the technology exists to generate an electric or magnetic field around the craft by supercooling superconductants, which creates zero electrical resistance, so a current can be circulated indefinitely. 

Nonionizing Radiation

Nonionizing radiation poses much less of a threat to astronauts. Possible effects include loss of memory, decreased perceptual threshholds, and cataract development, although test results and reports are inconclusive and conflicting. Generally the effects of nonionizing radiation in space are virtually harmless. Its sources include hypomagnetic conditions and UV radiation fromt he sun.

Extravehicular and Mars suits will be designed to protect the astronauts against dangerous exposure.