Murchison meteorite Australia

Analysis of carbon compounds—even amino acids—from extraterrestrial sources might provide deeper insights into this mystery. John Cronin and Sandra Pizzarello have examined the enantiomeric distribution of unusual amino acids obtained from the Murchison meteorite, which struck the earth on September 28, 1969, near Murchison, Australia. (By selecting unusual amino... 

The Murchison meteorite shown in Figure 6.7, like all meteorites, is named after the place from which it was recovered and in this case it is the town of Murchison, Victoria in Australia about 100 km north of Melbourne. The fall occurred in 1969 and was followed by an analysis of the chemical composition in some considerable detail. The Murchison meteorite is a carbonaceous chondrite containing about 2 per cent carbon, some as inorganic carbonates, and some as soluble compounds such as amino acids but the bulk as a macromolecular heterogeneous material referred to as kerogen. 

Interestingly, the proportions of the mostly racemic amino acids produced in this mixture are approximately the same as those found in fragments of the Murchison meteorite, which fell near the village of Murchison, Victoria, Australia in 1969.82,83... 

An alternative to the terrestrial synthesis of the nucleobases is to invoke interstellar chemistry. Martins has shown, using an analysis of the isotopic abundance of 13C, that a sample of the 4.6 billion year old Murchison meteorite which fell in Australia in 1969 contains traces of uracil and a pyrimidine derivative, xanthine. Samples of soil that surrounded the meteor when it was retrieved were also analyzed. They gave completely different results for uracil, consistent with its expected terrestrial origin, and xanthine was undetectable [48], The isotopic distributions of carbon clearly ruled out terrestrial contamination as a source of the organic compounds present in the meteorite. At 0°C and neutral pH cytosine slowly decomposes to uracil and guanine decomposes to xanthine so both compounds could be the decomposition products of DNA or RNA nucleobases. They must have either travelled with the meteorite from its extraterrestrial origin or been formed from components present in the meteorite and others encountered on its journey to Earth. Either way, delivery of nucleobases to a prebiotic Earth could plausibly have been undertaken by meteors. The conditions that formed the bases need not have been those of an early Earth at all but of a far more hostile environment elsewhere in the Solar System. That environment may have been conducive to the production of individual bases but they may never have been able to form stable DNA or RNA polymers this development may have required the less extreme conditions prevalent on Earth. 

Figure 6 The Murchison meteorite which landed at Murchison, Australia on September 28, 1969. Over / 00 kilograms of this meteorite have been collected. Classified as a carbonaceous chondrite, type II (CM2), this meteorite is likely to have come from a comet. More than 92 different amino acids have been Identified within the Murchison meteorite, nineteen of these are also found on Earth such that many believe that such meteorites provided the seeds of life on the early Earth.

Carhonaceous chondrites are also of interest because of the fascinating mix of relatively complex organic molecules they contain. Scientists have now discovered both amino acids and nitrogen bases in meteorites. Amino acids are the compounds of which proteins are made, and nitrogen bases are one of the building blocks of nucleic acids such as DNA and RNA. Researchers have found 92 amino acids in just one meteorite, the Murchison meteorite that fell about 60 miles (100 km) north of Melbourne, Australia, in 1969. Of these 92 amino acids, only 19 are found on Earth. Studies of other meteorites have shown that the Murchison results are not unique. In fact, amino acids occur in a number of carhonaceous chondrites. 

Some scientists speculate that many organic molecules required for life on the young Earth arrived on meteorites. The Murchison meteorite that landed in Australia in 1969 contained 92 different amino acids, including 21 found in Earth organisms. A skeleton structure (single bonds only) of one of these extraterrestrial amino acids is... 

Initial analysis of the Murchison meteorite that crashed in Australia in 1969 appeared at the time to answer two important questions. Careful study of die common amino acids found on the meteorite indicated that they were racemic (equal L and D). This established their extraterrestrial origin since the amino acids on Earth are L. In addition, it supported the intuitive notion that in space, in the absence of life, there is no intrinsic bias toward L- or D-amino acids. The findings from the Murchison meteorite lent support to the hypothesis of seeding the Earth with amino acids. 

O In the morning of September 28,1969, a carbon-containing chondrite fell to Earth in the neighbourhood of Murchison, Victoria (Australia). This actual meteorite disintegrated on entry into the Earth s atmosphere, and scattered its fragments over an area of five square miles. 

Direct evidence for the abiotic presence of fatty acids comes from the detection of fatty acids in the interior of the Murray and Murchison carbonaceous chondrite meteorites from Australia (up to C8), as well as an Asuka carbonaceous chondrite meteorite (A-881458) from Antarctica (up to C12) [84-87]. Fatty acids are relatively abundant in these meteorites, being 20 times more abundant than amino acids in the organic extract of A-881458. Indeed, organic extracts from the Murchison meteorite form boundary membranes when rehydrated [88, 89]. The presence of fatty acids is particularly suggestive because the chemical composition of these meteorites is believed to resemble that of the early solar system. 

The amino acids obtained from Miller s experiments were all racemic. Furthermore, only racemic amino acids were found on the Murchison meteorite which fell in Australia in 1969. This presents an interesting question How was optical activity introduced in complex molecules Among the various hypothesis, S. Akabori (46) proposed the following transformations for the synthesis of more complex polypeptides, which have been veri-... 

The fall of a carbonaceous chondrite in September 1969 near Murchison (85 miles north of Melbourne, Australia) was an event of great importance for scientists involved in meteoritic research. In 1969, many laboratories were well equipped to analyse the lunar samples, and interest in extraterrestrial matter was at its height when suddenly 83 kg of a carbonaceous chondrite were available. The biggest fragment... 

Before leaving the aminoacids problem, it is interesting to note that aminoacids have been detected in carbonaceous chondrites found in Antarctica. The risk of contamination is much less important in Antarctica than in Australia and this is one of the reasons why these studies were undertaken. They fully confirm the results obtained on Murchison 54,55), even if in one CM carbonaceous chondrite the amino acid content was only 10% of what was observed in Murchison 56,57). The contamination is in fact lower than in Murchison the aminoacid content was very similar for samples taken near the surface of the Antarctica chondrites or from their bulk. On the other hand, all the significant analyses on Murchison were performed on samples from the interior of the meteoritic fragments due to the high degree of surface contamination. In the case of the Allende meteorite, which has the same terrestrial age as Murchison, contamination was found to extend to a depth of more than 5 mm below the surface 52). 

Even more convincing than the spectroscopic proof of amino acids in the imiverse is the chemical analysis of chondrites (meteorites). Seventeen amino acids were discovered in the Murchison chondrite, which was found in Australia ten of these do not occur in Nature (on Earth). In terms of the total amino acid content of the Murchison chondrite, about one third consists of glycine. 

In 1969, a large meteorite landed near the town of Murchison, Australia. Chemical analysis of its organic molecules showed it possessed over 100 amino acids, including dozens not found on Earth. Some of the amino acids possessed enantiomeric excess (e.e.) to the extent of 2-15%, all in favor of the L-amino acids, the same enantiomers found in all of... 

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