Meteorite's Magnetite Martian Bacteria example essay topic

H.G. Wells wrote in his book, 'War of the Worlds', about Martian invasion toward earth. He mentioned, 'No one would have believed, in the last years of the nineteenth century that this world was being watched keenly and closely by intelligences greater than man's and yet as mortal as his own; that as men busied themselves about their various concerns they were scrutinized and studied, perhaps almost as narrowly as man with a microscope might scrutinize the transient creatures that swarm and multiply in a drop of water. ' Since then it has now been about 100 years Wells based his well-known story of human's first contact with extraterrestrial life. Now, in the 20th century scientists are starting to believe what was once a fictional story by writers now actually could be real, becoming the stuff of science. In 1994 scientists discovered fragments of meteorites which may in fact prove that signs of early life existed on Mars. Many of these meteorites are found in the Antarctica, extremely cold weathers aid in preserving and fossilizing the fallen meteorites for millions of years.

In order for scientists to conclude that the meteorites are from Mars and contain signs of fossilized life or traces of it they must provide sufficient evidence to support their theory. Today, a meteorite from Mars is being closely scrutinized by earthly intelligences. The famous meteorite to bare significant signs of life is the Allan Hills 84001 (ALH 84001), classified as one of the meteorites thought to come from Mars. Due to the atmospheric data taken by the Viking Lander spacecraft sent to Mars in the 1970's. The data make it possible to know that gases trapped inside the rock is identical to the Martian atmosphere. 'It is one of only 12 meteorites identified so far that match the unique Martian chemistry measured by the Viking spacecraft that landed on Mars in 1976's cient ist believed that the ALH 84001 blasted off from the surface of Mars about 16 million years ago by a comet or asteroid.

The rock orbited in the solar system for a few million years and finally reached Earth about 13,000 years ago. Investigation into the ALH 84001 and the possibilities for containing remains of ancient Martian life was assigned to a team of NASA scientists. Dr. David McKay, Dr. Everett Gibson and Kathie Thomas-Ker pta of Lock head Martin co-led the team with assistance from a Stanford team led by Professor of Chemistry Dr. Richard Are. They investigated different features in ALH 84001, trying to explain their origin and meaning and if these are evidence for life having once existed on Mars. The ALH 84001 is a rock formed originally from molten lava, containing small rounded carbonate mineral globules within the tiny cracks and fractures inside the rock. Within these carbonate minerals that the possibility of life existed on Mars is found.

Water is a necessity in all forms of like. It acts as a solvent and needed for chemical reactions. Therefore, the minerals are believed to have precipitated from a liquid, possibly water, which was percolating through the rock. The key features are 'carbonate globules'; contain mineral grains, which are similar to minerals produced by some bacteria on earth. Therefore it is possible that the mineral grains in ALH 84001 could have been produced by Martian bacteria and would be further evidence that life once existed on Mars.

These carbonates have hot been found in any other Martian meteorites. The ALH 84001 weighs about four pounds it was actually much bigger, due to the entrance through Earth's atmosphere the rock burned up to the size it is now. Researchers claim that 3 to 4 billion years ago water containing carbon dioxide percolated throughout the Martian rock that eventually became ALH 84001. This deposited carbonates inside the meteorite as well as organic molecules, minerals, and even the fossil remains of Martian bacteria that once flourished in the water. Within the carbonates, were findings of minerals that could be associated with life.

They found iron oxides and sulfides, which can be produced by anaerobic bacteria and other microbes. 'The team found unusual compounds -- iron sulfides and magnetite -- that can be produced buy anaerobic bacteria and other microscopic organisms on Earth' They also found magnetite, which is a form of iron associated with some earthly bacteria. The size, structure and purity of the magnetite's which can be produced biologically by bacteria on earth, thus they could have been formed by Martian bacteria. 'Impressed by the grains' resemblance in size, shape, and crystalline regularity to magnetite produced within some terrestrial bacteria, the researchers argued that bacteria also produced the meteorite's magnetite-martian bacteria, that is's uch minerals are usually produced as waste products and the grains in ALH 84001 are very similar in shape and structure to those produced by earth bacteria. The conditions under which these minerals were formed means they were probably formed through a biological process.

Although this evidence is very suggestive of life having once existed on Mars, it is possible that the mineral grains formed by a non-biological process as well. 'Some meteorites carry these compounds, presumably made by non biological processes' The samples analyzed may have been poor examples and have been interpreted in the wrong way. Secondly, the scientists identified organic carbon molecules that they believed originated on Mars. The organic carbon molecules called polycyclic aromatic hydrocarbons (PAHs) were found in and on the carbonate globules. They identify these PAHs as decay products of living organisms that flowed in when the carbonates were deposited.

PAHs are very common in the earth's atmosphere and occur from a variety of processes. The PAHs could have formed while the meteorite was in Antarctica and have entered it from the atmosphere. They could have occurred by entering the meteorite before it was found in Antarctica. If so it would be expected that the PAHs would be more common on the outside and become less abundant towards the center of the meteorite.

Investigation shows the opposite of this found and PAHs were more abundant towards the center of ALH 84001. This would be expected if it was extraterrestrial due to the meteorite burning up upn entry into the earth's atmosphere vaporizing PAHs near the surface. 'No PAHs were found in the meteorite's exterior crust, but the concentration of PAHs increased in the meteorite's interior to levels higher that ever found in Antarctica' Also the concentration of PAHs is greater that what would have been in the atmosphere at the time impacted. Again this makes the source more likely to be extraterrestrial. PAHs that occur in other meteorites within the galaxy their source is inorganic. Investigation with these meteorites and found that concentrations and the types of PAHs found in them were not similar to those found in ALH 84001.

If they had been it would suggest that the PAHs in ALH 84001 had been formed by the same inorganic process, but since they are not this could be interpreted as meaning they formed by another process, such as bacterial decay. The PAHs in ALH 84001 were also similar to those produced by bacterial decay on earth. Again there are limitations to these findings. It is possible that the PAHs on Mars may have originated from a source in space not sampled, for instance. This would lead to a false impression. However this evidence is very suggestive that the PAHs originated on Mars and could be from an organic source such as bacterial decay.

The final pieces of evidence are the shapes within the carbonate grains, which closely resemble fossils of bacteria. Found within the fracture of the carbonate mineral globules and are long, tabular, rounded and almost 'sausage' in shape. They are very small and can only be seen with an advanced electron microscope. If these features are the remains of fossilized bacteria, then this had to be proved as it was possible they could have formed from some inorganic process, or they may not actually be from Mars and be terrestrial, having entered ALH 84001 when it was in Antarctica. Many bacteria on earth were obtained which are similar in shape and size to those found in the Mars meteorite. Such bacteria also can be found in rocks and are often found in extreme environments.

Then it makes it possible that the structures could be fossilized bacteria. It is also possible that the features could be a result of the preparing of the rock for thin section under the electron microscope. This could be many things such as glue, residue or metals used to coat the sample. 'SEM generally requires that the sample be coated with a thin film of metal so that the SEM's electrons do not charge the sample and fuzz up the view. But coating samples with such metals, including the gold-palladium mixture usually can change texture, round off shapes and even create segmentation like the worm's' In order to disprove this possibility, other rocks samples were prepared, not containing the bacteria structures, in the same way ALH 84001 was prepared.

Upon examination of these slides, no features, which resembled bacteria, could be seen and there the structures must not have been preparation errors and are actually part of the rock. It was also possible that the shapes were the remains of terrestrial bacteria, as they did resemble bacteria found within other rocks. 'The analyzed rocks are similar in composition to terrestrial andesites and close to the mean composition of Earth's crust' Other meteorites from Antarctica were looked at for evidence of bacteria, which would be terrestrial; it would be likely that the structures in ALH 84001 would also be terrestrial in origin. None could be found and it is probable that the structures in ALH 84001 are extraterrestrial. Despite these findings and conclusions, it is still possible that the structures are not Martian bacteria fossils. They could be the result of inorganic processes, and they do not show any real evidence that they were once living, such as cell structures or being in the reproduction stage.

It is also still possible that they are the remains of earth bacteria that somehow entered ALH 84001 but not the other meteorites, for reasons such as unsuitable chemistry. Therefore, the presence of these structures in ALH 84001 is not sufficient to prove that life once existed on Mars. There are good evidence that prehistoric life may have once existed on Mars in the form of bacteria. However, this does not show that life now exists ALH 84001 or on Mars. These findings are very controversial and debatable, with other reasons for formation and occurrence. It is very possible that these findings were lots of coincidences that give the false impression that life once existed.

This is the best evidence ever found for the existence of extraterrestrial life and although the chances are far off, it is possible. The findings have evoked great interest into Mars and with more research and money going into the investigations an absolute conclusion can be provided about finding out if life did once exist on Mars. At this time there is no definite answer to whether the findings on the ALH 84001 are significant signs of life or there was life on Mars at one time. We will have to wait until humans or robots go there and test samples directly or bring them back to Earth for analysis. Till then there is no way to actually prove the findings from the ALH 84001.

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