Possibility of Life on Mars - Essay Example

Life On Mars Contents Introduction What are the conditions needed for life on Mars 2 What are the signs of life that we look for 2 How do we search for life 3 Current conclusions 3 Analysis The Viking landers 4 Meteorite from Mars 5 Conclusion 6 Bibliography 7 Introduction What are the conditions needed for life on Mars Water is one of the most important elements on Earth, it is impossible for any living thing to survive without water. While this is not necessarily the case on another planet, it is likely that if life has ever survived on Mars it would need water. Some scientists believe that there was once water on the surface of Mars, and there is a possibility that there is still water present below the surface if the results obtained from Mars Global Surveyor are correct (NASAs Mars Exploration Program, 2007). There is currently definitive evidence to show that there is ice present at the poles on Mars. All living things need a source of energy on which to survive. While here on Earth many organisms rely on the Sun to supply this energy, not all do. There are some organisms that live to far down in the oceans for the sunlight to ever penetrate, and there are other organisms that live below the surface of the Earth where it would be impossible for them to ever benefit from sunlight as a source of energy. These organisms rely on chemical or geothermal energy instead, and it is likely that organisms living on Mars would have to rely on sources of energy similar to these types of organisms; it is very unlikely that there would be any life present on the surface of Mars because the atmosphere contains chemicals known as superoxides, which break down all organic, or carbon-containing molecules, which are the building blocks of life. It is much more likely that if life ever was present, or still is there today, that it would be found under the surface. What are the signs of life that we look for The signs that we use to look for life on Mars are all based on knowledge that we have of life on Earth. While any life forms found on Earth may not be remotely similar to those found here, it provides a good starting point for the search. All living things on Earth contain the element carbon in their structures, and so this if we find this element on Mars it could signify areas in which life may have developed. From looking at deposits of fossils which chart the history of life on Earth, it can be seen that there are only certain environments in which fossils can be preserved, so if a appropriate set of conditions is found on Mars then it may be a good place to look for fossilized life forms. How do we search for life There have been several expeditions carried out to Mars, but so far all by machinery rather than actual people. In the 1970s, a team of scientists, including Dr. Gilbert Levin, sent two Viking probes up to the surface of Mars to look for signs of life. They conducted tests on the soil to see if organic materials, and possibly life, were present there at the moment, producing controversial results. Since then we have sent several other probes to conduct testing on the soil, and there are a pair of robots there at the moment - Spirit and Opportunity. As well as conducting tests, these robots have been taking photographs that a panel of scientists are studying, which may give further clues as to whether life is there at the moment, how likely it is that life has ever been there, and where best to look for any life that may be present. Dr. Gilbert Levin is also one of the scientists currently involved with this expedition. As of yet there have been no manned missions to Mars, but this may change in the future, since there are many scientists who back this idea. Current conclusions At the moment the question as to whether life is present, or has ever been present, on Mars is largely unanswered. Dr. Gilbert Levin concluded in 1997, from the results of the Viking mission, that there is currently life on Mars, in the form of bacteria in the soil. He maintains to the current day that he is correct, and is aiming to gain further evidence to support his claims from the current mission to Mars (David, 2004). While the majority of the scientific community appears to disagree with Dr. Levin's opinion, there does not appear to be any specific evidence that has been presented to show that his opinions are incorrect, there appears only to be a great deal of speculation that his theories are incorrect. There has however been more evidence surface that life on Mars existed in the past, through the discovery of a meteorite that came from Mars millions of years ago. Again, there is much controversy surrounding the results of testing on the meteorite, with many scientists from outside of NASA arguing that the results may not be indicative of life, but with no conclusive proof that they don't. Here I will show the evidence that has so far been presented with regard to life on Mars, and why some people argue that the results so far do not prove that it exists. Analysis The Viking landers In the 1970s the Viking landers were sent to Mars to explore the surface and hunt for signs of life. The experiments that the machines were designed to carry out were based on a very limited knowledge of Mars, since no other landing on Mars had previously taken place, and when the results came back from the expedition, they were very ambiguous and have caused much controversy since. There were two main experiments that the machines were designed to carry out to show whether or not organic compounds (carbon-containing) were present in the soil; one of these produced negative results, but the other gave positive results. Most scientists were, and still are, adamant that the positive result was produced because of a chemical reaction in the soil on Mars that was due to one chemical compound mixing with another, but there is one scientist who maintains that these results, without a doubt, show that bacteria are present in the soil on Mars. The scientist in question is Dr. Gilbert Levin, and he is actually the designer of the test which gave the positive results; he was also the principal investigator of the results given by the Viking devices. He also claims that the first test, which gave the negative results, was flawed in the fact that it wasn't sensitive enough. He went on to prove his point by carrying out the same experiment in the antarctic, where surprisingly, it also gave negative results. Since we know without a doubt that there are many species of bacteria residing in the Antarctic, this showed that it is possible that the test gave false results on Mars, but many scientists still refuse to believe that this is enough evidence of life (ALH84001, n.d.). Meteorite from Mars In 1996, scientists announced to the world that they had found evidence of fossilized life on a meteorite that had originated on Mars. The meteorite was created around 15 million years ago when a comet or an asteroid hit the surface of Mars, and it is estimated to have landed on Earth around 13 thousand years ago, landing in the Antarctic, where it was discovered in 1984. NASA have been studying the rare meteorite ever since, and have concluded that there is definite evidence of life held in it. Carbonate globules As mentioned in the introduction, all living things contain carbon in their structures. Although carbonate can also be found in non-living materials, NASA concluded that the carbonate found here was consistent with the carbon you would expect to find in living organisms Polycyclic Aromatic Hydrocarbons These are compounds that are created by bacteria, and these were also present in the meteorite. Many other scientists have argued that these don't show evidence of life on Mars, but that in fact they show that the meteorite has been contaminated since being in the Arctic. NASA have so far not been able to give definitive evidence to the contrary. Magnetite globules These are something created by bacteria, but many scientists do not believe that they were created until the meteorite reached Earth. Microscopic fossil-like structures The photos of these show small worm-like structures, but it is difficult to tell whether they are actually fossilized bacteria or just mineral deposits. While the pictures that were taken of them are quite stunning, there are still many scientists who are skeptical of what they actually show. Conclusion While there is evidence to show that life on Mars is possible, the majority of the evidence presented so far shows only that appropriate conditions are present for life, and do not conclusively show that these conditions have been successfully utilized by bacteria, or any other form of life. However the evidence presented is enough to warrant further investigation, since they show the possibilities of life are there. The unwillingness of many to accept the proof offered by Dr. Levin and other scientists so far may be rooted in the trepidation of the implications that life on Mars could hold. If it was found that there was, or has been life on Mars in any form, it would show that the initiation of life my be less selective and down to chance than we currently believe, and would also suggest that there is a strong possibility that there are other reservoirs for life in our own solar system, not to mention the thousands of other planets in the galaxy. At the moment there are several things which limit the search for life on Mars. The first of these is technology. While we are aware of what the properties are of life on Earth, we cannot be sure that the same properties are going to hold for organisms on another planet. Developments need to be made in technology that can distinguish living organisms from non-living materials, even if the characteristics of the organism are not the same as those we would expect, based on our knowledge of terrestrial organisms. The second is that many scientists have argued that remote-controlled probes are not suitable for finding the correct samples to bring back for further study. They claim that the only way to ensure appropriate samples are collected is to send a trained geologist; there are many scientists now lobbying for a mission to send people to Mars for the first time. Bibliography ALH84001 - The Life On Mars meteorite (n.d.). Retrieved on April 5 2007, from http://www.marsnews.com/focus/life/ David, L. (2004, August 3) Life On Mars Likely, Scientist Claims. Retrieved on April 5 2007, from http://www.space.com/scienceastronomy/mars_microorganisms_040803.html Harland, D.M. (2005) Water and the Search for Life on Mars. New York: Springer. NASAs Mars Exploration Program (2007). Retrieved on April 5 2007, from http://mars.jpl.nasa.gov/ Schopf, J.W. (1999)Life On Mars: Tempest in a teacup Proceedings of the American Philosophical Society, 143 (3) Sept, pp. 359-379. Read More