Life-form can exist on Mars: There has been much evidence put forward contributing to the theory of a biological life-form on Mars
Having been studied for decades, Mars shows the most suitable conditions, of all the planets in our solar system, for our presumptions of evolution of life.
Life-form can exist on Mars
It is believed by many that there are too many factors such as UV radiation and extreme temperature environments which could inhibit a life-form on Mars. Although the distance from Earth to the Sun is considerably less than that of the Sun to Mars, our atmosphere protects living organisms on Earth. Studies have shown that an atmosphere is present on Mars through the identification of an insignificant ozone layer, however this atmosphere is not the most suitable for living organisms but unlikely to be a life limiting factor (Cockell, et al., 2000). Some arguments which both oppose and agree with the theory of extra-terrestrial life include studies carried out by the Viking Explorers and MER programmers which landed on Mars. These man-made devices studied the atmosphere and the top layer of soil to discover a very high oxidation factor which could inhibit growth by converting living matter to CO², as well as studying sedimentary rocks on the surface of the planet. The search for life on Mars shows interesting differences in both personal theories and scientific studies.
Analyses and Results of the Martian Meteorite ALH84001
The Viking and MER Missions
The first Viking mission was launched in the summer of 1976. It consisted of two orbiters, which had a main objective of photographing the planet from orbit, and two landers, which studied the surface of the planet. The main emphasis was on photography, in which orbiter 1 produced over 10,000 pictures, taken from the planets orbit(Snyder & Evans, 1981).
In 2003, two rovers were launched, called Mars Exploration Rovers. The objective of this mission to Mars was study and to determine whether Martian conditions and it’s atmosphere could support the theory of a possible life-form having ever existed on the planet (Squyres & Knoll, 2005). The MER missions include the Rovers; Spirit and Opportunity which carried out surveys and analyses on the surface of Mars.
The two Rovers covered specific regions known as Gusev and Meridiani Planum respectively for over a year and a half. The Rover Opportunity landed on the surface of Mars on January 24th and traveled through two craters (Eagle and Endurance) while carrying out experiments on both craters.
Experiments and Results from Viking and MER programmers
Aerosols and water vapor were detected in the Martian atmosphere by the Viking orbiter and other scientific research objects, which included: Mars Global Surveyor (MGS), Mars Atmospheric Water Detector (MAWD) and Thermal Emissions Spectrometer (TES). This water vapor was detected in the North Polar region during Spring and Summer seasons. MAWD detected twice as much vapor in the region than any of the other orbiters (Pan kine, et al., 2009). The detection of water in the Martian atmosphere contributes a large amount of evidence to support the theory of a suitable atmosphere for a biological life-form to exist.
Hematite was discovered on the surface of the planet, by the rover Opportunity, in the Meridiani Planum. This mineral form of iron-oxide is a possible preservative for per-biotic and biotic processes carried out on the surface of Mars. These processes are carried out on Earth in rock varnishing, in which micro-colonial fungi and bacteria are present in rock varnish matrices, which were documented in America and Australia (Allen, et al., 2004). It is believed that water did once flow on the surface of Mars through the discovery of rippled like curves, indicating that streams once flowed through the Meridiani Planum (Horneck).
Ancient, sedimentary rocks were also found at Meridiani plain by the Rover Opportunity, which consist of sandstone composed of sand grains which consisted of a variety of sulfate salts formed by erosion and re-deposition (Squyres & Knoll, 2005). One of the most important findings of the mission however was a record of aqueous processes found on the Meridiani plain both in surface and sub-surface regions. Although these aqueous processes were identified, there is still no record of liquid water on the surface of Mars. Any water present on Mars, is found in the atmosphere as water vapor, located at the north Polar region.
Because of a thin atmosphere and an insignificant ozone layer, the surface of Mars is exposed to high UV radiation, which includes UVA, UVB and UVC. UV radiation is known to be a cause of DNA damage and mutation in bacterial species and also more developed life-forms. UV radiation is also known to inhibit photosynthesis in plants. Life-forms on Earth contain processes that protect them from exposure to UVA radiation. However, because of high UVB and UVC radiation exposure to the Martian surface, and also conditions such as extreme temperature changes and a lack of liquid water on the surface, it is unknown for any life-form to withstand such conditions(Cockell, et al., 2000).
In order to understand and examine bacterial behavior under exposure to this high UV radiation, an experiment was carried out by Scheurger et al.. Seven different Bacillus spp. were exposed to conditions similar to that of the Martian surface. The Bacillus spp. were exposed to the radiation in time sets of 0, 0.25, 0.5, 1, 5, 15, 30, 60, 120 and 180 minutes. The bacteria were prepared for the experiment as thin mono layers of endospores. The results showed that B. pumilus SAFR-032 (surviving for 180 minutes) was the most resistant to the Martian conditions, while B. megaterium and B. subtillis 42HS-1 (which were inactivated after 30 minutes) were the least sensitive under exposure of high UVB and UVC radiation.
It is very difficult to conclude whether or not life does or even did exist on the surface or in the Martian atmosphere. Evidence from both sides of the theory are being analyzed in extreme detail in order to come to a conclusion. The analyses and study of the Martian meteorite ALH84001, is considered the most studied and detailed analyses ever to be carried out on an igneous rock. Even with this extent of analyses being carried out on the meteorite, we still cannot come to a clear and concise conclusion to whether or not it contained traces of extra-terrestrial life. Although the detection of carbonate globules and bacterial shaped objects suggests that life theoretically could have existed on the planet of Mars, scientists who oppose the theory of extra-terrestrial life disagree that these discoveries indicate a life-form present in the meteorite. They suggest that because of the small size of these bacterial-shaped objects that they could represent artifacts in the meteorite.
There was also some criticism about the Viking and MER missions. Although a small amount of atmospheric water vapor was observed, the lack of liquid water on the surface declares this evidence inconclusive. However there was some very interesting discoveries made by the Rover Opportunity, including the detection of hematite. This mineralised form of iron-oxide can be used for the preservation of aqueous processes. This discovery, along with the discovery of ripple-like curves in the Meridiani plain, could indicate a past life-form having existed on the surface of the planet many years ago.
I believe that an extra-terrestrial, biological life-form could have existed on the surface of Mars, in past decades or even centuries. Evidence from both the Mars Exploration missions and the study of the Martian meteorite, ALH84001, provide much contribution to the theory that life did exist on the planet in the past. It is clear that life cannot survive in the Martian atmosphere at present because of extreme conditions. The exposure to high UV radiation, extreme temperature changes and also a lack of liquid water on the surface indicate to me that these conditions are not only unfavorable to the survival of a life-form but are far too extreme for a biological life-form to survive for a significant time frame.
In relation to the theory of Panspermia, I believe that it can be justified by the experiment carried out by D.Stöffler et al.. If the bacteria shaped objects found in the meteorite prove to be biological life-forms this piece of evidence could explain another widely investigated theory of where and when life began on Earth. Through the study and analyses of Mars and its atmosphere, I believe that many of the questions and theories about life on Earth can be answered.