01-19-2020, 05:46 AM
Material older than the Solar System (Murchison meteorite) now shows biochemical and related substances.
The Murchison meteorite is one of the most studied meteorites due to its mass (>100 kg or 220 lb) and the fact that it was an observed fall. It fell in Australia in 1969 near Murchison, Victoria. It belongs to a group of meteorites rich in organic compounds.
In January 2020, astronomers reported that the oldest material found on Earth to date is the silicon carbide particles from the Murchison meteorite, which have been determined to be 7 billion years old, about 2.5 billion years older than the 4.54-billion-year age of the Earth and the Solar System.[a] The published study noted "dust lifetime estimates mainly rely on sophisticated theoretical models. These models, however, focus on the more common small dust grains and are based on assumptions with large uncertainties."
Murchison contains common amino acids such as glycine, alanine, and glutamic acid as well as unusual ones such as isovaline and pseudoleucine.[8] A complex mixture of alkanes was isolated as well, similar to that found in the Miller–Urey experiment. Serine and threonine, usually considered to be earthly contaminants, were conspicuously absent in the samples. A specific family of amino acids called diamino acids was identified in the Murchison meteorite as well.[9]
The initial report stated that the amino acids were racemic and therefore formed in an abiotic manner, because amino acids of terrestrial proteins are all of the L-configuration. Later the amino acid alanine, which is also a protein amino acid, was found to have an excess of the L-configuration,[10] which led several scientists to suspect terrestrial contamination according to the argument that it would be "unusual for an abiotic stereoselective decomposition or synthesis of amino acids to occur with protein amino acids but not with non-protein amino acids".[11] In 1997, L-excesses also were found in a non-protein amino acid, isovaline,[12] suggesting an extraterrestrial source for molecular asymmetry in the solar system. At the same time, L-excesses of alanine were found in Murchison, but with enrichment in the isotope 15N,[13] however, the isotopic pairing was contested later, on analytical grounds.[14] By 2001, the list of organic materials identified in the meteorite was extended to polyols.[15]
Compound class[16]
Concentration (ppm)
Amino acids 17–60
Aliphatic hydrocarbons >35
Aromatic hydrocarbons 3319
Fullerenes >100
Carboxylic acids >300
Hydrocarboxylic acids 15
Purines and pyrimidines 1.3
Alcohols 11
Sulfonic acids 68
Phosphonic acids 2
Total
>3911.3
The meteorite contained a mixture of left-handed and right-handed amino acids; most amino acids used by living organisms are left-handed in chirality, and most sugars used are right-handed. A team of chemists in Sweden demonstrated in 2005 that this homochirality could have been triggered or catalyzed, by the action of a left-handed amino acid such as proline.[17]
Several lines of evidence indicate that the interior portions of well-preserved fragments from Murchison are pristine. A 2010 study using high resolution analytical tools including spectroscopy, identified 14,000 molecular compounds, including 70 amino acids, in a sample of the meteorite.[18][19] The limited scope of the analysis by mass spectrometry provides for a potential 50,000 or more unique molecular compositions, with the team estimating the possibility of millions of distinct organic compounds in the meteorite.[20]
https://en.wikipedia.org/wiki/Murchison_meteorite
The Murchison meteorite is one of the most studied meteorites due to its mass (>100 kg or 220 lb) and the fact that it was an observed fall. It fell in Australia in 1969 near Murchison, Victoria. It belongs to a group of meteorites rich in organic compounds.
In January 2020, astronomers reported that the oldest material found on Earth to date is the silicon carbide particles from the Murchison meteorite, which have been determined to be 7 billion years old, about 2.5 billion years older than the 4.54-billion-year age of the Earth and the Solar System.[a] The published study noted "dust lifetime estimates mainly rely on sophisticated theoretical models. These models, however, focus on the more common small dust grains and are based on assumptions with large uncertainties."
Murchison contains common amino acids such as glycine, alanine, and glutamic acid as well as unusual ones such as isovaline and pseudoleucine.[8] A complex mixture of alkanes was isolated as well, similar to that found in the Miller–Urey experiment. Serine and threonine, usually considered to be earthly contaminants, were conspicuously absent in the samples. A specific family of amino acids called diamino acids was identified in the Murchison meteorite as well.[9]
The initial report stated that the amino acids were racemic and therefore formed in an abiotic manner, because amino acids of terrestrial proteins are all of the L-configuration. Later the amino acid alanine, which is also a protein amino acid, was found to have an excess of the L-configuration,[10] which led several scientists to suspect terrestrial contamination according to the argument that it would be "unusual for an abiotic stereoselective decomposition or synthesis of amino acids to occur with protein amino acids but not with non-protein amino acids".[11] In 1997, L-excesses also were found in a non-protein amino acid, isovaline,[12] suggesting an extraterrestrial source for molecular asymmetry in the solar system. At the same time, L-excesses of alanine were found in Murchison, but with enrichment in the isotope 15N,[13] however, the isotopic pairing was contested later, on analytical grounds.[14] By 2001, the list of organic materials identified in the meteorite was extended to polyols.[15]
Compound class[16]
Concentration (ppm)
Amino acids 17–60
Aliphatic hydrocarbons >35
Aromatic hydrocarbons 3319
Fullerenes >100
Carboxylic acids >300
Hydrocarboxylic acids 15
Purines and pyrimidines 1.3
Alcohols 11
Sulfonic acids 68
Phosphonic acids 2
Total
>3911.3
The meteorite contained a mixture of left-handed and right-handed amino acids; most amino acids used by living organisms are left-handed in chirality, and most sugars used are right-handed. A team of chemists in Sweden demonstrated in 2005 that this homochirality could have been triggered or catalyzed, by the action of a left-handed amino acid such as proline.[17]
Several lines of evidence indicate that the interior portions of well-preserved fragments from Murchison are pristine. A 2010 study using high resolution analytical tools including spectroscopy, identified 14,000 molecular compounds, including 70 amino acids, in a sample of the meteorite.[18][19] The limited scope of the analysis by mass spectrometry provides for a potential 50,000 or more unique molecular compositions, with the team estimating the possibility of millions of distinct organic compounds in the meteorite.[20]
https://en.wikipedia.org/wiki/Murchison_meteorite
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