After Earth, Mars is considered to be the most habitable planet in our solar system due to several similarities. To mention a few:
- Both Mars and Earth rotate and revolve on their axes. Earth tilts at 23.5 degrees, while Mars tilts slightly more at 25.2 degrees.
- They both have 4 seasons each, Earth’s seasons being more versatile. However, the average temperature on Mars is about -80 °F (Humans will have to build and live in climate controlled, synthetic bubbles).
- The length of day on Earth is 24 hours and slightly longer on Mars at 24 hours 37 minutes. A year is 365 days on Earth and almost double on Mars at 687 days.
- Mars has water, frozen underground and at the polar ice caps, like those in the Arctic regions on Earth.
- Mars holds other elements needed for life to exist Carbon and oxygen in the form of Carbon dioxide, Nitrogen as well as Hydrogen.
So, what is it that is making us take a back step from venturing into Mars? The answer would be-‘the heavy amounts of radiation’.
Earlier, it was believed that after the safe landing of our explorers on the surface of Mars, the planet would provide shielding from the depredation of radiation, but up to what extent was unknown. Radiation and its various forms have influenced the planning of human and robotic missions, as well as the search for life taking place on Mars.
Radiation humans are exposed to in space
There are three kinds of space radiation:
- Galactic cosmic rays(GCR) generated outside the solar system;
- Solar particles emitted by the sun during solar prominence;
- Radiation trapped by the Earth’s magnetic field.
On the surface of the Earth, these types of radiation are not notable health hazards because the Earth’s atmosphere and magnetosphere (i.e. the Earth’s magnetic field) protect us from most of the radiation from space. This protection is received by the Astronauts in low Earth orbits, but once they travel outside this protective shell, it becomes a problem. Since Mars lost its magnetosphere about 4.2 billion years ago, its atmosphere is considered to be trivial by scientists.
Effects of Radiation on the Human Body
A study comparing the mortality rates of lunar astronauts travelling to different levels of the orbit showed that numbers of cardiovascular disease-related deaths among the deep space astronauts were significantly higher. The rate among astronauts who never flew was 9%, among low-Earth orbiting astronauts 11% and for the men who traveled to the Moon, a staggering 43% clearly 4-5 times higher than the less traveled.
Researchers demonstrated the effects of these radiations on mice as well. After six months of exposure to similar type of radiations the mice exhibited cellular breakdown and impaired arteries, which if occurred in the human body would lead to cardiovascular diseases.
Exposure to cosmic radiation-particularly charged high energy protons causes permanent damage to DNA molecules, capably shutting the repair system of the body.
Acute effects of exposure would include changes to blood, nausea, diarrhea and sometimes vomiting which are generally mild and curable. The major concerns about space radiation are its long term effects which include cognitive and memory changes causing diseases such as Alzheimer’s; cataracts, circulatory diseases, increased susceptibility to cancer and even sterility. Sometimes these health effects appear in the descendants of the exposed individuals due to skipping of generations of the mutated genes.
At low doses, such as those we receive every day on Earth from background radiation (e.g. radiation emitted by rocks, solar radiation etc.) cells have the ability to repair the damage rapidly. At higher doses, it becomes difficult for the cells to repair themselves leading to permanent damage, sometimes even leading to their death. Cells that change permanently can go on to produce other abnormal cells, which under favorable conditions become cancerous. If the mutation occurs in a sperm or egg cell, mutations pass on to the offspring. At very high doses the cells cannot be replaced as rapidly as required and hence the tissues fail to function.
There are two ways by which radiation damages the cells:
- The body water absorbs a large fraction of the radiation and ionizes to form highly reactive, water derived radicals. These free radicals act on DNA molecules by breaking chemical bonds.
- The radiation collides head on with the DNA molecule.
Either way the DNA molecule breaks. Breaks generally occur at either one or both the strands of DNA, but the breaks to both strands are consequential as repair becomes difficult and the cells may either change permanently or die.
Flying to Mars definitely exposes us to Cosmic rays as well as energetic solar particles; both type of radiations having the ability to damage DNA damage and increasing the risk of cancer several folds. If a person gets cancer on Mars, there will be no chemotherapy available at the colony making cancer an agonizing death sentence. The bottom line is, ‘Mission to Mars will affect the genetics and change the course of humans forever.’ Do we really want that to happen?
Article by Srividya