One of the most prominent ways of transforming into a superhuman as shown in movies is to get hit by high-energy radiation. It was radiation that transformed Dr. Banner to the hulk and Johnny to the human torch. Space can provide such a Radiation environment, but unlike movies, these Radiations can be harmful. So what are the possible damages that an astronaut can get when exposed to high levels of space radiation?
SPACE RADIATION COMPOSITION:
Space radiations comprise the harmful Galactic Cosmic Rays (GCR), Solar Energetic Particles (SEPs) as well as the particles trapped in the Earth鈥檚 Magnetic field. The energy range and flux of these radiations are considerably high that during manned missions they can pose severe health risks to the crew ranging from mild effects like disorientation to more severe effects like cancer.
QUANTIFYING SPACE RADIATION:
The effect of damage that different kinds of radiation (GCRs or SEPs) can cause on a material (spacecraft or human body) is non-identical. To quantify the effect of radiation on a material, values of absorbed dose should be calculated. The energy deposited in an absorbing material per unit mass is called an absorbed dose (D). Traditionally used unit is rad (1rad=100 ergs/gram). The S.I unit is called Grey and is defined as 1Gy=1J/Kg. The interconversion between rad and Grey is 1Gy=100rad.
HEALTH EFFECTS:
Initial radiation exposure can lead to what is called Acute Radiation Syndrome (ARS). ARS was initially identified from those who were exposed to low-energy radiation like Gamma rays (as in the case of atomic bomb survivors in Japan). Such effects were also found in astronauts during early space travel. The threshold for ARS is 0.1 to 0.2 Gy. When the radiation level crosses 1 Gy, the blood cells number gets reduced, our immune system becomes compromised and the probability of cataract formation increases. Lymphocyte cells (the core of our immune system) are the most radiation-sensitive resulting in their high depletion as compared to other cells. When the radiation level crosses 4 Gy, the skin starts to redden and then peels off. Other symptoms include nausea, vomiting, and diarrhea. If diarrhea occurs within a short time after exposure, it implies that a severe dose is being imparted and could be fatal.
CANCER:
Prolonged exposure to space radiation can also lead to cancer, but this is an ambiguous result and only probabilistic approaches can be made rather than deterministic ones. The basic reason for this is that cancer can be also due to heredity or lifestyle habits. Radiations can cause aberrations in DNA leading to their breakage. Usually, the cell has mechanisms to join the DNA when they are broken. However, this attempt becomes futile if high-energy radiation is involved in the breakage process.
WHAT NEXT!!
Till now we talked about the effects of space radiation. Obviously it looks like it is not safe to go to Mars. But is that it or are we missing some points? Maybe there any ways we can protect our astronauts from these harmful radiations?
Stay tuned for the next post where I will talk about radiation protection methods.
REFERENCES USED:
Benton E.R and Benton E.V, Space radiation dosimetry in low-Earth orbit and beyond, Nuclear Instruments and methods in physics, Vol. 184, 2001.
Charles W. Lloyd, Scott Townsend, Katherine K. Reeves, Space Radiation eBook, NASA Human Research Program Engagement and Communication
Janice. H, Carnell. L, Blattnig. S, Chappel. L, George. K, Lumpkins. S, Simonsen. L, Slaba. T, Werneth. C, Risk of Radiation Carcinogenesis, NASA Human Research Program, 2016.
