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Introduction
For many years now, people have theorized how and when all life on Earth can no longer be sustained. Whether it is the theory that Earth itself will explode or that the conditions on Earth will become too extreme to support life or any other of the many theories, it is uncertain when this inevitable event will occur. This is one of the reasons why Mars exploration is so important today. Mars is the fourth planet from the Sun, neighbouring Earth and Jupiter. It is approximately 229 million km from the Sun and 55 million km from Earth. Mars is 6790 km in diameter which is around half the size of Earth. It is also called the Red Plant because of its bright rusty colour from oxidized iron minerals in the soil that cover its surface1**. The ultimate goal of Mars exploration programs is to be able to compare its qualities to the qualities of Earth that has made it possible for Earth to sustain life. NASA (National Aeronautics and Space Administration) defines life as a self-sustaining chemical system capable of Darwinian evolution . Darwinian evolution suggests that all organisms develop through natural selection to increase their overall fitness in their specific environment2. Scientists are interested in exploring Mars rather than other planets because it is believed that it used to have the potential to host life. Today, Mars is cold and dry, but there is compelling evidence that is used to be much warmer and wetter. An example of this is the finding of sedimentary and volcanic rock on Mars. The formation of sedimentary usually requires water and volcanic rock is the solidification and cooling of molten rock3. Mars is also close to Earth in comparison to the other planets so it is less expensive to get rovers there and it is also much easier and has a higher success rate of landing because of the shorter distance. Currently, there is no solid evidence of any life forms, past or present,
on Mars. However, there have been previous mission that have found promising observations. Some pieces of evidence include; small quantities of methane have been found in Mars atmosphere that can be an indicator for microscopic life, the Viking lander found positive results for chemical reactions in organisms, the Curiosity rover that found compounds necessary if microscopic life was present, and meteorites that contain bacteria-resembling structures on them4. However, these findings are not significant enough to indefinitely prove that Mars has ever been or currently has potential to be populated by microbial life.
Statement of Aim:
The objective of this report is to determine whether life has ever been present on Mars or whether Mars has the potential to support any life forms.
The Potential for Life on Mars
There are many different factors that contribute to making a planet habitable. These factors must also be proportionate with each other because the slightest imbalance can result in a volatile environment that is ultimately unlivable. In order for a planet to be habitable, the surface must have an average temperature of minus 15ÚC to 115ÚC as liquid water can still exist under those conditions, it must have water readily available, it must have a sufficient-sized atmosphere to protect itself from radiation and/or meteorites, it must have a steady source of energy, and it must have nutrients present. Many studies have determined that Mars has potential to become habitable but would require certain technologies and advancements. In order to maintain long-term habitation on Mars, we would have to learn how to convert the abundance of raw Martian materials into other essential resources.
Many of the gases most prevalent in Mars atmosphere, including carbon dioxide, nitrogen gas and argon, which takes low power to separate and has been taking place on Earth for over a century now. Nitrogen is compulsory for life. It is found in all proteins and in organic materials, foods and many other Earth components5. Nitrogen makes up 78% of the Earths composition. Nitrogen also makes for a thick enough atmosphere to stabilize liquid water on the planets surface. When the atmosphere is not thick enough, water will vaporize. There is proof that billion of years ago, on Mars, the atmosphere was thick enough to hold liquid water on its surface. The Viking Orbiter, which was sent to Mars in 1975, brought back images with evidence of surface water6.Today, Mars atmosphere is too thin for water. The reason for Mars thinning is believed to be because of its light gravity and its lack of global magnetic field, making Mars vulnerable to solar winds from continuous pressure from the sun.
This would strip the lighter molecules, thinning out the overall atmosphere of Mars, which also lead to the cooling and drying out of Mars7. Carbon dioxide is needed in the planets atmosphere to sustain life because it protects the planets surface from radiation and keeps the planet warm8. Argon can also be separated with technologies and used for converting to resources necessary for maintaining life. Now, Mars is very dry compared to Earth. It has polar caps with water-ice and carbon dioxide dry ice. The water has potential to be purified and consumed or electrolyzed in order to make oxygen and/or hydrogen. This possible supply of water and other natural gases provide optimism that there is potential for life on Mars with some modifications. The third piece of evidence that Mars meets living requirements is the amount of available energy. Surface abundance measurements of hydrogen and carbon monoxide were taken of Mars. The measurements were taken during a study in 1988 by Lellouch et al. that mapped out the wave observations of carbon monoxide isotopes using a radiotelescope9.These observations displayed that only a small fraction of the available gases were actually being consumed and used for energy. This means that there is a large percentage of unused energy available for organisms to use10. More research needs to be conducted in order to get specific answers to the question of whether or not Mars has the potential to sustain life. However, there is also the possibility that we have already come across life on Mars but are just unable to recognize this life form because of its unique qualities11.
Analogue Studies of Life on Mars
Since recent Mars missions have concluded that there used to be a presence of water on its surface, it has increased peoples inclinations that Mars was housing some form of life or still currently is. As Mars thinned out, it lost its moisture and became cold. The water pockets dried into saline brine pockets within the permafrost. These pockets could potentially be a home for extant Martian microbes or the last refuge of an extinct organism. Deposits that come from the evaporation of salt-water are called evaporites. On Earth, some evaporites have bacterial and algal accumulations. Those organisms are most likely halophiles, which are organisms that survive best in salty conditions. A study was done to determine the survival potential of microbes in frozen evaporites. Different types of halophiles were subjected to a freeze-thaw cycle under dry conditions by washing them in high concentrations of sodium chloride.
Each of the different halophiles used in this experiment survived at different conditions, whether it was being exposed to a higher sodium chloride concentration for a longer period of time, or they were incubated at a lower temperature. The survival rates were specific to the needs of the individual halophiles from their environment. However, E. Coli and P. Fluorescens did not survive the drying or freezing process. The data recorded from this experiment proposes that certain halophilic microbes can survive extremely dry and/or coldconditions, similar to the environment on Mars. There may be evidence of extinct halophiles in brine pockets within the permafrost or even possibly evidence of extant Martian microbes currently thriving in extreme conditions12. Another analogous study using Mars-like conditions investigated the effect of fatigue and long working hours on cognitive performance. 30 astronauts were selected to perform an experimental simulation in the MDRS (Mars Desert Research Station in Utah), which is an analog Mars surface habitat13. 10 of the members selected were commanders and the other 20 members had positions that required lower amounts of leadership.
The experiment spanned over 14 days. The groups were tested on day 1, 7 and 14. They had to complete salivary cortisol level testing, heart rate variability testing , muscular fatigue testing and their sleeping patterns were also observed. They were also asked to fill out a subjective questionnaire, rating their sleepiness, as well as completing neuro-behavioural tests. The average working hours of the leadership group over the course of this simulation was significantly higher than the normal group. The leadership group also reported to be more fatigued. There were no other significant differences in the results and most importantly, the overall cognitive functioning and developmental performance score was not significantly different between the two groups14. Based on the results of this study, one can assume trained individuals can perform adequately under extreme conditions, increasing the chances of a successful mission, potentially for discovering life forms on Mars.
Conclusion
The search for life on Mars, or previous life forms on Mars, is ongoing. While there have some pieces of evidence proving that Mars is capable of sustaining life, it is not significant enough. If information can continuously be gathered about the qualities of Mars, it can provide more answers as to why Earth can sustain life and what next steps humans can take in order to make Mars a habitable planet.
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