Secret of life on Earth found in meteorite
Discovery of DNA building blocks found in space rocks confirms theory, according to scientists
The building blocks for life on Earth may have arrived in a meteorite landing billions of years ago, a study suggests. Analysis of three meteorites has spotted evidence of all four of the core materials that make up DNA, potentially proving the long-held scientific theory that the key components for life were transported to Earth from space via a meteorite around 3.5billion years ago. Previously only two of the four main components of DNA had been found in space rocks.
‘The DNA chemicals could have been incorporated into asteroids during solar system formation’
‘Meteorites hit Hadeanera Earth at a higher rate, so a large number of DNA base pairs may have been delivered’
THE creation of life on Earth can be traced back billions of years to when a meteorite landed, according to a study by scientists.
Experts have long debated how Earth, one of trillions of planets created in the universe’s 14billion-year existence, managed to cultivate life.
One theory was that the core materials that make up DNA were transported to Earth from space via a meteorite around 3.5billion years ago.
During this period Earth would have been constantly burning, peppered by meteorites and comets from a chaotic and formative solar system, and it is possible at least one impact brought with it the constituent parts of DNA.
But while this theory had much support in the scientific community, it had had one glaring weakness: only two of the four main components of DNA had been found in space rocks.
Now state-of-the-art analysis of three meteorites has spotted evidence of all four, proving that the necessary jigsaw pieces for life are found in space.
Scientists say it is possible these basic ingredients could have been deposited on Earth by a meteorite and formed life. “[The DNA chemicals] could have been generated by photochemical reactions prevailing in the interstellar medium and later incorporated into asteroids during solar system formation,” the researchers write in their study, published in the journal Nature Communications.
“This study demonstrates that a diversity of meteoritic nucleobases could serve as building blocks of DNA and RNA [ribonucleic acid] on the early Earth.”
DNA underpins all forms of life. Its double-helix structure is formed by two strands of molecules connected along their length by ladder-like rungs made of two chemicals joined together.
There are four chemicals – adenine, thymine, cytosine and guanine – known as “bases” and their arrangement makes up an individual’s genome. The order of these four bases is unique in every person and provides their genetic code.
Previously, scientists had found evidence of guanine and adenine in meteorites, but had never spotted their complementary partners.
A team of Japanese researchers, led by Hokkaido University, obtained two samples of the Murchison meteorite, which landed in Australia in 1969 and one sample from both the Murray and Tagish Lake meteorites, which landed in the USA in 1950 and Canada in 2000, respectively.
They were ground into a fine powder and subjected to hypersensitive analysis capable of detecting molecules at the parts per trillion level. More than 30 chemicals were identified, including the four vital DNA ingredients of adenine, guanine, cytosine and thymine.
“Given that extraterrestrial materials, including meteorites, were provided to the Hadean Earth at a flux much higher than that in the present day, a large number of these canonical base pairs may have also been delivered to the Earth at that time,” the researchers write.
“The accumulation of these scarce molecules has substantial geochemical challenges on Hadean Earth with an atmosphere possibly dominated by carbon dioxide and nitrogen.
“Hence, we expect that the exogenous base pairs contributed to the emergence of genetic properties for the earliest life on Earth.”