Abstract
The acceptable reality for now is that no research has managed to conclusively show or document that there is life or no life in Mars. This research paper is of the opinion that the argument about life or lack of it in Mars should seize, until such a time when conclusive evidence to support arguments on either side will be attained. Until then, researchers need to do the hard work of verifying or refuting existing theories and counterchecking any new evidence that could be contained in the Martian meteorites
Is there evidence of life on Martian meteorites?
According to Buseck et al, Nanocrystals of Magnetite(Fe3O4) compounds in meteorites found from mars are the strongest, yet the most controversial indicators that there is extraterrestrial life in Mars(13490). The allegation attached to the Fe3O4 is that they resemble crystals found in Meteorite ALH84001, which are formed by specific terrestrial bacteria. The ALH84001 was found in the Antarctica and later recognized as meteorite whose origin was Mars(Mckay et al 924).
McKay Et al authored startling report based on chemical and structural features of ALH84001 (295).The report indicates that there was indeed life in mars. McKay Et al based their arguments on four chemical and structural features of the meteorite and although they admitted that the individual features could not prove their allegation, they sought to convince the general public as well as scientists that the four features taken collectively were evidence enough that there was indeed life in Mars(Friedmann et al 562).
The first basis for their conclusion was the “igneous Mars Rock”. According to their report, the rock was of unidentified geologic context and had pores and fractured spaces that were permeated by a fluid. Their second reason was that the igneous rock was older than the carbon globules found there in. The third reason was that the TEM and SEM images captured of the carbon globules had features that resemble microfossils, terrestrial-biogenic-carbonate structures, and terrestrial micro organisms.
Fourth, the Fe-sulfide and magnetite particles indicated that the oxidation and other reductions reaction had occurred on the compound, thus indicating the presence of microbial systems and finally, there were Polycyclic Aromatic Hydrocarbons(PAHs)on the compound thus indicating that its original surface(Mars)had carbonate globules(McKay et al 930).
Buseck et al, notes that although the McKay et al theory has been criticized and largely questioned, no one scientist or researcher has been able to disapprove it(13490).The report starts by acknowledging the fact that the 1975 Viking lander experiments managed to negate the possibility that there was life on Mars.
However, the report states that the conclusion from the tests cannot be meant to conclude that there was absolutely no life in Mars. This was especially because the Viking experiments were too localized to offer a conclusive report regarding life or lack of it in Mars(McKay et al 924).
The deduction by McKay Et al that meteorite ALH84001 has enough evidence regarding life in Mars has been criticized by many scientists with Thomas-Keprta et al(2164) saying that the evidence offered was based on “presumptive bio-signatures”. In their own research, Thomas-Keprta et al classified Fe3O4 crystals and identified them to be similar to the intracellular magnetite released by MV-1(a magnetotactic bacteria-strain).
In the research, Thomas Keprta et al states that the magnetite populations are chemically pure and from a single-domain(2164). They also observe a “unique” crystal habit, which they define as truncated hexaoctahedral(2164). They argue that since there are no known reports which could explain the truncated hexaoctahedral observations, the presence of the MV-1 strain of bacteria was most likely as a result of Natural selection rather than organic activity.
They however argue that the only possibility where the magnetite crystals could be used to indicate that there is life in Mars, is if there are “unexplained inorganic processes on Mars that are absent on Earth and hence forms the truncated hexa-octahedral magnetite” (2165). Overall, Thomas-Keprta et al manages to support rather disapprove the McKay et al deduction that the ALH84001 is an indicator that there is life in Mars.
Their argument does not however go unchallenged. Buseck at al, states that the “Truncated hexa-octahedral” crystals they refer to are not as unique as they make people to believe (13494).Buseck et al argues that the term means that the crystals of ALH84001 have a combination of octahedron, dodecahedron and cube faces. These according to them had been observed in other meteorites and hence were not a unique aspect at all.
Buseck et al(13490) criticizes both studies done by Mckay Et al(929)and Thomas-Keprta et al(2165) saying that the two arguments are flawed. He claims that without the micro structural or chemical evidence to back the allegation that the features in the ALH84001 are indeed magnetite crystals, then any evidence produced thereafter is inadmissible.
He further argues that magnototactic bacteria are ever-present on the Earth, despite the fact that intact chains of the nano-sized magnetite crystals from such bacteria are hard to find in earthly geological samples.
As such the intact chains as found by McKay et al(925)would be hard to find because it would be unlikely that they would survive biological processes. Friedman et al acknowledges that it is quite difficult to understand how the magnetite chains hypothesized by McKay et al survived in their intact form(2176).This only serves to cast further doubt on the allegation of McKay et al and subsequent research conducted and documented by other authors like Friedman et al and Thomas-Keprta Et al(2164-2169).
Golden et al neither refute nor support the allegation by McKay et al(370-375).They however proved that just as much as the formation of carbonates, sulfides and magnetite on ALH84001 could be attained in temperatures that support life, the same can be formed inorganically. Golden et al through a combination of precipitation and heating processes developed simple inorganic process, which they claim can offer an alternative explanation to the carbonate, Fe-sulfide and magnetite found in the meteorite ALH84001(370).
The acceptable reality for now is that no research has managed to conclusively show or document that there is life or no life in Mars. This research paper is of the opinion that the argument about life or lack of it in Mars should seize, until such a time when conclusive evidence to support arguments on either side will be attained. Until then, researchers need to do the hard work of verifying or refuting existing theories and counterchecking any new evidence that could be contained in the Martian meteorites.
Discussion
By2007, there were 12 meteorites that had been studied or still were being studied for ingredients that would suggest life on Mars. The meteorites were thought to have originated from Mars due to their unique(often peculiar) chemistry (Kimball 1). Of all the 12, the ALH84001 has been the single most meteorites subjected to extensive study.
The three most cited ingredients in the ALH84001 that suggest that there could be indeed life processes in Mars are the presence of PAHs. However, scientists note that PAHs are not unique to meteorites from Mars only. According to Kimball, meteorites from other places in the solar systems are known to have PAHs too even though it has been established that there are no traces of life there(1).
The mineral within the meteorite(magnetite, carbon and Fe-sulfide)is the other indicator that some scientists use to suggest the presence of life activities in Mars. However, as seen above, some researchers have proven that it is quite possible to generate the minerals without biological processes.
The time that the minerals were deposited in the meteorite is also suspect because as Kimball(1)indicates, the minerals seems to have been deposited in the specific rock later in its history, which raises the question, is it possible that the rock picked the minerals on earth rather from its origin? Stephan et al notes that the rock had fusion crusts, and mineralogical and well as chemical differences(113).
These differences could have led to the contamination of the inner rock through the cracks, which could have happened during handling or in the Antarctic environment before the rock was discovered.
An answer to this question is provided by Stephan et al, who after a study concluded that it was highly unlikely that the PAHs in the ALH84001 had an extraterrestrial origin(113). The study further provided evidence that the meteorite was contaminated by lead, which is evidently a terrestrial material. Studies by Golden et al also allude that ALH84001 continues to be contaminated with terrestrial microbial materials hence suggesting that ‘maybe’ the PAHs had been picked in its Antarctica location (374).
The third reason that some researchers like McKay et al (924) and Thomas-Keprta et al(2164)suggests indicates some signs of life are the objects that resemble fossils in tiny micro-organisms when observed under a microscope.
This argument is however discredited by Kimball, who argues that the fact that the largest of the “nano-fossils” got from the rock had a diameter of 100 nanometers, is evidence enough that it does not have the necessary volume to support life(1).The Smallest microorganism on earth is the Mycloplasmas and has 300 nanometer diameter. Scientists indicate that a micro-organism would need at least a 200 nanometer diameter in order to support life (Kimball 1).
In addition to the ALH 84001 meteorite, other meteorites of Martian origin include “Shergotty, Nkakhla and Chassigny”. Nakhla was the first meteorite of Martian origin to be found on earth(Glavin et al 8835), and just like the LAH84001, the meteorite contained carbonates and some hydrous minerals. Research on Nakhla indicated that the rock had been exposed to some aqueous solutions after its formation, and this was the first indication that researchers need to conclude that in deed there were aqueous processes on Mars.
The length of time that such processes persisted however remains a pertinent question to this day. As opposed to ALH84001 meteorite which had an estimated terrestrial age of almost 13,000 years, the Nakhla meteorite fell on 9 am 40 kilometers to the East of Alexandria in Egypt in 1911. The fall was observed and most of the specimen rocks were collected within days of the fall (Glavin 8834).
On observation, Nakhla was found to contain d-amino acids, which were not present in the ALH84001 meteorite. According to Glavin et al, the d-amino acids were not extraterrestrial in nature and had been deposited into the rock when it hit the ground in the Nile region (8836).
This conclusion was reached because in addition to finding similar d-amino- acids around the Nile soil, the amino acids would have been racemic if they were formed on Mars(Glavin 8836). The D/L ratios, which could have determined the amino-acids of Martian origin in the rock, were not possible due to the low concentration of the same.
Another meteorite EETA79001 was found to contain l-enantiomers components of amino-acids (Mcdonald & Bada 1179).Such are common in proteins and thus indicated that this rock too had been exposed to terrestrial contaminants, specifically from the Antarctic ice where the meteorite had been collected.
Is (was) there life in Mars?
According to Glavin & Bada, life in Mars just like on earth would be possible in the presence of water and “a continuous supply of pre-biotic organic compounds”(1022). The exogenous delivery of meteorites on earth from Mars has given researchers and scientists the chance to determine if indeed there was or there is life in Mar. Unfortunately this is not always possible due to the exposure of the meteorites to different substances as they fall to earth and on impact with the earth.
Other attempts to identify whether there is life in Mars collectively known as the Viking Studies involved the placement of television cameras on Mars surface to detect any presence of life. This turned no results. Gas chromatograph and Mass spectrometer were also used for purposes of checking the Martian soil for organic molecules.
This too showed negative results. The labeled-release equipment was set up to check for catabolic activities by microorganisms that could be present in the Martian soil. Again, the result for this was negative. The Pyrolytic-release experiments turned negative too and had been set to capture any anabolism evidence that could be generated by microorganisms that would be in the Martian soil.
Finally, a gaseous exchange experiment was conducted on Mars but showed no biological evidence in gaseous formation. The Viking studies showed that there were no signs of life in Mars(at least not as we know it one earth). However, the meteorite evidence could be a possible answer to the question that has been nagging scientists for decades now.
Conclusion
Although there is a possibility that there is evidence contained in the Martian Meteorites that life was or still is in Mars, researchers face enormous challenges in proofing the same.
The single most challenge lies in avoiding the exposure of Martian meteorites to terrestrial environments. Right from Nakhla to ALH84001,it is evident that terrestrial environment is able to affect the rocks thus making it even harder to determine if the observations made on such are endogenous or simply as a result of the contamination from terrestrial environments.
Evidently, whether there is life on Mars or not is a subject that needs more research. Unfortunately, studies by (Buseck et al 13492; Golden et al 375)indicates that meteorites like ALH84001, Nakhla and EETA79001 show different components between different researches thus indicating that their exposure to the terrestrial environment is making them less valuable for research as the days go by.
As indicated in my thesis statement, researchers should concentrate on deciphering any evidence to either side, which can be deducted from the available meteorites.
Works Cited
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Friedmann, Imre, Wlerzchos, Jacek, Ascaso, Carmen & Winklhofer, Michael. “Chains of Magnetite Crystals in the Meteorite LAH84001; Evidence of Biological Origin.” Proceedings of the National Academy of Sciences of the United States of Americ. 98.5 (2001):2178-2181.
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Glavin, David & Bada, Jeffery. “ Isolation of Purines and Pyrimidines from the Murchison Meteorite using Sublimation.”Lunar and Planetary Science Xxxv (2004):1022-1023.
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Thomas-Keprta, Kathie, Clemett, Simon, Bazylinski, Dennis, Kirschvinki, Joseph, McKay, David, et al. “Truncated hexa-octahedral magnetite crystals in ALH84001: Presumptive Bio-Signatures” Proceedings of the National Academy of Sciences of the United States of America 98.5(2001):2164-2169.