Tuesday, April 26, 2022

PANSPERMIA
Life on Earth was started by a meteorite, new evidence suggests

Joe Pinkstone
 Apr 27 2022


There are few questions bigger than how life on Earth began, and a new study may have finally proven that our existence can be traced back to a meteorite landing on our planet billions of years ago.

Experts have long debated how Earth, just one of trillions of planets created in the universe’s 14-billion-year existence, managed to cultivate life.

A leading theory has claimed that the core materials that make up DNA were transported to Earth from space via a meteorite around 3.5 billion years ago when our planet was a fiery hellscape in its celestial infancy.

During this time it was constantly peppered by meteorites and comets due to a chaotic and formative solar system, and it is possible at least one impact brought with it the constituent parts of DNA.


NASA
A new study may finally have proven that our existence can be traced back to a meteorite landing.

But while this theory had much support, it has had one glaring weakness; until now, only two of the four main components of DNA had been found in space rocks.

However, fresh analysis of three meteorites using state-of-the-art methods has spotted evidence of all four, proving that the necessary jigsaw pieces for life are indeed found in space.

Scientists say it is possible that these basic ingredients could have been deposited on Earth by a meteorite before life began.

“[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.


123RF
A leading theory claims the core materials that make up DNA were transported to Earth from space via a meteorite around 3.5 billion years ago

“This study demonstrates that a diversity of meteoritic nucleobases could serve as building blocks of DNA and RNA on the early Earth.”

The double-helix of DNA is one of the most famous chemicals in the world and it underpins all forms of known life.

DNA is made of two strands that weave around each other like an interminable ribbon and are connected in the middle by ladder-like rungs made of two chemicals joined together.

There are four such chemicals (adenine, thymine, cytosine and guanine, better identified by their initials A, T, C and G) which are known as “bases” and their arrangement makes up an individual’s genome.

Every person’s order of these four bases is unique and provides the code for personality, appearance, health and everything in between.

Previously, scientists had found evidence of guanine and adenine in meteorites, but – despite intense searching – 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 US 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.


GREG PRICE
Scientists had previously found evidence of guanine and adenine in meteorites, but despite intense searching had never spotted their complementary partners.

More than 30 chemicals were identified in total, including the four vital DNA ingredients.

“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.”

The Telegraph

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