| Radiation |
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The radiation out in space differs from that on Earth in that particles move at such a high speed that its impact causes ionization. This is called ionizing radiation, and it causes all types of damage to human cells. One of the more dangerous results is a mutation in DNA that can lead to cancer. The amount of radiation an astronaut receives depends on orbital inclination, altitude above the earth, solar cycle, and individual susceptibility.
The Earth’s atmosphere protects us from harmful radiation, but when humans travel out into space, they are susceptible to life-threatening amounts of a more dangerous radiation. Earth radiation consists of Alpha particles (helium), Beta particles (electrons or positrons), and Gamma particles (electro-magnetic radiation). Space radiation, however, are atoms that have lost their electrons as they accelerated at speeds approaching the speed of light so that only a nucleus remains. The effects of this radiation are more drastic than that of earth radiation. The speed of a particle of space radiation ionizes any atom it strikes by knocking away electrons. This type of radiation is therefore also known as ionizing radiation. Ionization damages human cells and causes adverse effects, the most severe being damage to DNA. In addition, radiation may damage nearly every part of the body, such as through inflammation or paralysis. Here we will examine the danger of damage to DNA.
Perhaps the most dangerous result of exposure to space radiation is damage to DNA. DNA, or deoxyribonucleic acid, is composed of nucleotides and carries the genetic information in the cell and instructions on reproducing them. Radiation can directly collide with the DNA molecule, ionizing and causing instant damage, or it can undergo a chain reaction in which the water in the body absorbs a large portion of radiation and becomes ionized. When ionized, it forms highly reactive molecules that react with and damage DNA. Damaged DNA can change the physical arrangement of a chromosome or alter the nucleotide sequence of DNA. This results in a mutation that is usually undesirable and can be passed on to offspring. Mutations lead to cancer, a malignant growth or tumor caused by abnormal and uncontrolled cell division.
The amount of radiation an astronaut receives depends on orbital inclination, altitude above the earth, solar cycle, and the individual’s susceptibility. Because the Earth’s magnetic field attracts ionizing radiation, an orbit closer to the earth’s poles will be subject to higher radiation. There is also less protection against ionizing radiation farther from Earth, where the magnetic field does not pull away radiation. Because the Sun is prone to intensive solar flares at the end of its 11-year cycles, radiation emitted increases. Researchers are currently searching for ways to lessen radiation damage. Chemoprevention, or the use of chemical agents, drugs, or food supplements to prevent disease, is one option. In a space station, when a radiation storm occurs, astronauts head toward a shelter. However, astronauts in spacecraft are more exposed during radiation storms and damage is more severe.
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