Meteorite DNA may be linked to the origins of life
Scientists have recently discovered that meteorites contain all four of the main building blocks of DNA. These space rocks may have brought these building blocks to Earth. DNA is composed of nucleobases, or pairs of amino acids, in a spiral staircase structure. Each step of the DNA spiral contains two nucleobases – adenine and guanine. Researchers first discovered these compounds in meteorites in the 1960s.
Detection of single isomers
Amino acid enantiomers in meteorites are enriched in the enantiomer isoleucine and a small amount in the enantiomer isolevulinic acid. Isoleucine forms enantiopure crystals while isolevulinic acid is racemic. The amino acids in meteorites have a rich mixture of inorganic and organic components and exhibit a wide range of enantiomeric abundances.
Detection of single isomers is possible by performing solid-state 13C-NMR analyses of the amorphous carbon in meteorites. The abundance of aliphatic carbon is higher than the aromatic carbon signal in meteorites like NWA 7020 and 801, and the ratio of aliphatic/aromatic chemical shifts can help in determining the extent of chemical oxidation of the organics in meteorites associated with water. The ratio of carbon isotopes in meteorites was also determined by using sensitivity-modified element analyzer/isotope ratio mass spectrometers and nitrogen isotope mass spectrometry (EA/IRMS) to examine aliphatic/aromatic isomers.
Sugars were also found in meteorites but not in their natural abundance. However, previous studies have shown that the sugars in meteorites were extracted using a solution of hydrochloric acid and water. The hydrochloric acid extract was purified to yield aldonitrile acetates, which have substantial advantages over the traditional method. This method is already being used for carbon isotope analysis of sugars in biological samples.
Detection of low concentrations of nucleobases
Recent research by scientists at Hokkaido University has found evidence of a few nucleobases in several meteorites. Two of these molecules are purines and pyrimidines. While these elements are not essential for life on Earth, they are important for the development of organic chemistry. If detected, they could resolve the debate about panspermia.
The first meteorites that scientists detected contained nucleobases. Scientists made promising discoveries, but their work was halted by the difficulty of finding all the purines and nitrogen bases. Eventually, advances in analytical techniques enabled scientists to detect the molecules in small amounts, several orders of magnitude lower than previously detected concentrations. The researchers believe the first samples of meteorites to contain nucleobases were composed of DMT.
To investigate these potential bacterial origins of meteorites, the authors analyzed the Murchison #1 extract and the cation-desalting fraction for the presence of nucleobases. These compounds were then subjected to ultrapure water extraction, which allowed them to be detected. Once identified, the authors concluded that their meteorites contained a variety of organic compounds, including dicarboxylic acids.
Detection of chiral sugars
The discovery of chiral sugars in meteorites is a significant step towards understanding the evolution of life on Earth. Meteorites contain all the building blocks of DNA, including amino acids, sugars, and RNA. Scientists are now using meteorites to understand how these compounds evolved. Scientists are able to detect these sugars by analyzing the carbon in meteorites.
The scientists have found chiral sugars in two different meteorites. The left-handed form of aspartic acid is chiral, while the right-handed version is known as chiral sugars. All three of these amino acids are involved in the process of glucose metabolism and are non-biological. However, the findings support the hypothesis that these sugars were produced by extraterrestrial life. If so, it could mean that life on Earth originated from space and came here to establish its existence.
The researchers also found left-handed amino acids in a tagish lake meteorite. However, no other signs of life were found in the meteorite. However, they did find three amino acids in the chiral form. These compounds did not have the exact 50-50 ratio of left-handed amino acids, indicating that they were formed by bacteria. Although these results are preliminary, the discovery of chiral sugars in meteorites may pave the way for studying the origins of homochirality, a property that is vital to the chemistry of life.
Detection of pyrimidines
Researchers have discovered that the DNA molecule contains three types of nucleobases: adenine, guanine, and uracil. These three nucleobases are essential for the double helix structure of DNA. Scientists had previously only identified uracil in meteorites, but this new finding sheds light on the possible origin of DNA and other genetic material.
Previous studies had detected seven purine bases and one pyrimidine in meteorites, but previous methods had used a hot formic acid extraction method that might have destroyed the nucleobases. To avoid this, the new research group used a milder method. They used high-resolution mass spectroscopy to identify the nucleobases in parts per trillion. They also used liquid chromatography to analyze the structural isomers of these nucleobases.
This method has several advantages. Researchers have already used this method to extract nucleobases from the asteroid Ryugu. The Hayabusa2 mission will bring samples of Ryugu to Earth in late 2020. The OSIRIS-REx mission is scheduled to return with samples from Bennu in 2023. And because it’s not necessary to heat samples before analysis, it is a highly effective method.
Detection of adenine
Meteorites are known to contain organic compounds, such as adenine. Since the 1960s, scientists have been studying meteorites for the presence of these elements. Some other compounds that have been detected in meteorites include uracil, cytosine, and thymine. However, these elements are particularly hard to detect in meteorites. A geochemist from Hokkaido University in Sapporo, Japan, developed a technique for extracting chemical compounds from liquified meteorite dust.
This compound contains two rings, the first of which requires a tiny boost of energy from the star. The second ring self-assembles without any outside help, and the ringed structure allows it to absorb excess energy and form concentrated clouds. Adenine is a relatively simple compound, and could have formed from the surface of a planet, but the theory of how the molecules were formed remains a mystery.
Although the presence of adenine and cytosine in meteorites raises the possibility that life on Earth was formed in the early universe, scientists are unsure of the origin of the compounds found in meteorites. Researchers think that they may have been generated by photochemical reactions during the formation of the solar system. However, there is another possibility that the presence of these elements in meteorites may have helped early life develop its genetic functions.
Detection of guanine
Purines are the building blocks of DNA and RNA and are abundant in most fossils and living organisms. Purines are found in several types of meteorites, but they are most abundant in guanine. These substances have been found in meteorites from the Antarctic continent, but their presence does not correlate with their abundance in terrestrial environments. As a result, it is difficult to determine the source of these compounds in meteorites, although there are other possibilities.
DNA and RNA are made of five basic building blocks called nucleobases. DNA uses the ACGT letter code to form its chains, while RNA swaps thymine for uracil. Astronomers have studied meteorites and found guanine and adenine at concentrations of eleven to twenty milligrams per gram. The presence of these compounds is a good indication of how long life has existed on Earth.
While this study is still preliminary, detecting guanine in meteorites is an important step toward discovering whether life began on Earth. Astrobiologists are currently trying to learn more about the origin of life and how it evolved. They believe that these compounds originated in the early solar system and were incorporated into asteroids as the solar system formed. In the early Earth, these organic molecules hitchhiked onto meteorites.
Detection of uracil
Researchers have been detecting organic compounds in meteorites since the 1960s, including uracil, cytosine, and thymine. However, despite their recent discoveries, the two building blocks have remained elusive. Now, however, scientists have developed a technique that allows them to extract these compounds from the liquified meteorite dust. Geochemist Yasuhiro Oba, from Hokkaido University in Sapporo, Japan, developed this technique to extract these compounds.
DNA is made up of five building blocks, called nucleobases. Each one of these nucleobases contains a specific amino acid and a sugar molecule, which together form the genetic code. DNA contains all five building blocks, while RNA has one fewer than five, allowing researchers to deduce the presence of all five building blocks. Meteorites contain adenine and guanine, which scientists say could be evidence of life on Earth. While the other two building blocks of DNA, cytosine and thymine, are missing in meteorites, uracil is the only amino acid in the samples.
The study’s findings are a landmark for the search for extraterrestrial life, paving the way for the discovery of alien life. The first meteorite sample to be identified as a source of uracil was found to contain a trace amount of uracil, although the abundance of uracil was not quantified. The next discovery is a discovery of the missing pyrimidine nucleobase, thymine.
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Provided by Antonio Westley
Disclaimer: This article is meant to be seen as an overview of this subject and not a reflection of viewpoints or opinions as nothing is definitive. So, make sure to do your research and feel free to use this information at your own discretion.