The Earth is the only planet that is known to support life, but it was not always inhabited. Approximately 4 billion years ago, something occurred that provided the necessary components for life on Earth, such as amino acids. While the origins of these amino acids on Earth are not fully understood, some scientists believe they may have been brought to the planet through meteorites.
A recent study has examined the potential for certain types of meteorites called chondrites to produce their amino acids through reactions fueled by gamma rays emitted by the meteorites. Chondrites are a type of stony meteorite that contain small, round objects known as chondrules. Chondrules are made up of silicate minerals and are some of the oldest objects in the Solar System, as per Cosmos.
Meteorites have struck the Earth since the planet's formation and some of these early impacts may have included carbonaceous chondrites. These are rare types of chondrite that contain significant amounts of water and small molecules, including amino acids.
Delivering Necessary Life Ingredients
It is possible that these meteorites delivered the necessary ingredients for life to the Earth, but it is still not clear how these compounds formed on the meteorites. The new study suggests that chondrites, or the objects from which they originated, may have the ability to produce amino acids through certain reactions. However, it is important to note that this is just a theory, and further research is needed to fully understand the origins of amino acids on Earth and whether or not meteorites played a role in their formation.
The researchers, led by Yoko Kebukawa a cosmochemist from Yokohama National University in Japan, sought to address questions from previous laboratory experiments that explored the possibility of amino acid formation on carbonaceous chondrites. These earlier experiments showed that simple molecules like ammonia and formaldehyde could produce amino acids, but only in the presence of heat and liquid water.
In the new study, the researchers investigated whether the heat required for amino acid production could potentially come from the meteorite itself, in the form of gamma rays. Early carbonaceous chondrites are known to contain aluminum-26, a radioactive element that releases gamma radiation as it decays. Kebukawa and her team wanted to determine whether this decay could generate enough heat to create amino acids. To conduct the research, the scientists dissolved ammonia and formaldehyde in water and sealed the resulting solution in glass tubes. They then exposed the tubes to high-energy gamma rays from decaying cobalt-60.
Studying Meteorites' Amino Acid
As the dose of gamma radiation increased, the production of various amino acids such as alanine, glycine, α-aminobutyric acid, and glutamic acid, as well as β-amino acids like β-alanine and β-aminoisobutyric acid, also increased. The researchers suggest that these amino acids may be able to explain the presence of these compounds on carbonaceous chondrites that have landed on Earth, such as the Murchison meteorite in Australia.
The Murchison meteorite is a famous space rock that landed on Earth in Victoria, Australia in 1969. It has since been extensively studied and is known for its high concentration of amino acids, including more than 70 different amino acids, many of which are not found on Earth. The Murchison meteorite is also notable for containing "presolar" silicon carbide particles, which are older than the Sun. This has led to widespread interest in the possibility that the basic building blocks of life may be able to form easily in other places in the universe. In their study, Kebukawa and her team sought to understand how amino acids might form on a meteorite like the Murchison meteorite and how long this process might take, as per Museum Victoria.
Following their findings and estimates of the amount of gamma radiation that would have been emitted by decaying aluminum-26 in meteorites, the researchers estimate that it would take between 1,000 and 100,000 years for this process to generate the amount of alanine and β-alanine found on the Murchison meteorite. While there is still much to learn about the process of abiogenesis or the spontaneous generation of life, the researchers suggest that this study provides evidence that reactions driven by gamma rays can produce amino acids on a meteorite, which may have contributed to the origin of life on Earth. The study analysis was posted in the journal ACS Central Science.
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