Life on Earth may have been seeded by special radioactive space rock, study suggests

Radiation may have provided heat needed to make life-building block molecules, scientists say

A special kind of meteorite with radioactive elements could have potentially sparked life on Earth, a new study suggests.

Researchers have previously theorised that meteorites may have delivered amino acids and other similar life-building block molecules, initiating the origin of life on Earth.

A new study, published on Wednesday in the journal ACS Central Science, has demonstrated that amino acid molecules could have formed in these early meteorites sparked by gamma rays produced inside the space rocks.

Since the formation of Earth over 4 billion years ago, meteorites have periodically bombarded the planet at high speeds, including the one known to have contributed to the extinction of dinosaurs.

Scientists, including those from Yokohama National University in Japan, suspect that if these initial space rocks had included a class of meteorites called carbonaceous chondrites, the early bombardments may have contributed to the seeding of life on Earth.

Some of the carbonaceous chondrite meteorites, they said, contain significant amounts of water as well as small organic molecules, and also produce energetic gamma rays that can drive the chemical reactions to form amino acids.

Until now, the source of amino acids in meteorites has been hard to pinpoint.

While previous studies have shown that chemical reactions between simple molecules like ammonia and formaldehyde can synthesise amino acids, liquid water and heat are also required.

Research has also shown that some early chondrite meteorites contained radioactive forms of elements like aluminum that release a form of high-energy radiation called gamma rays when they decay.

The new study showed experimentally that this radiation could have provided the heat needed to make life-building block molecules.

In the research, scientists dissolved formaldehyde and ammonia in water and sealed the solution in glass tubes.

They then irradiated the tubes with high-energy gamma rays produced from the decay of a form of cobalt.

As the total gamma-ray dose increased, researchers observed the production of α-amino acids, such as alanine, glycine, α-aminobutyric acid, and glutamic acid, as well as β-amino acids, such as β-alanine and β-aminoisobutyric acid.

“We discovered that gamma-ray irradiation of aqueous formaldehyde and ammonia solutions afforded a variety of amino acids,” scientists wrote in the study.

Based on the study results, they estimated that it may have taken between 1,000 and 100,000 years to produce the amount of alanine and β-alanine that was found in the Murchison meteorite which landed in Australia in 1969.

The findings suggest chemical reactions catalysed by gamma rays on meteorite parent bodies can produce amino acids and may have likely contributed to the origin of life on Earth.

“Our findings indicate that gamma rays may contribute to amino acid formation in parent bodies during aqueous alteration. In this paper, we propose a new prebiotic amino acid formation pathway that contributes to life’s origin,” researchers noted.