Gamma-rays may have helped meteorites seed Earth with the building blocks of life

three bright streaks in sky above rocky black surface with patches of red lava
An illustration of meteorites, possibly carrying the building blocks of life, bombarding the infant Earth. (Image credit: NASA's Goddard Space Flight Center Conceptual Image Lab)

New research may have solved the puzzle of how amino acids formed within the space rocks that are thought to have seeded Earth with the building blocks of life.

During the violent early epoch of the solar system, high-energy gamma rays may have triggered chemical reactions that created the amino acids within these meteorites, which then bombarded Earth, kick-starting the origins of life, scientists propose in a new study.

Meteorites are made from the material left over from the formation of the solar system's planets around 4.5 billion years ago and frequently smashed into the surfaces of young planets, including the initially sterile Earth, during the earliest epoch of the solar system. 

Related: Meteorites reveal how they brought space water to Earth

Scientists think that if that early bombardment included a class of meteorites called carbonaceous chondrites — which contain significant amounts of water and small molecules, such as amino acids — this space-rock delivery system could have contributed significantly to the emergence of life on our planet.

Yet how these molecules formed within meteorites in the first place has remained a puzzle — one that Yokohama National University astrobiologist and cosmochemist Yoko Kebukawa and her team think they may be on a path to solving, according to a statement (opens in new tab)

In previous experiments, Kebukawa and colleagues had shown that reactions between simple molecules, such as ammonia and formaldehyde, can synthesize amino acids and other macromolecules. But for this to happen, liquid water and heat would be required.

The team wanted to know if this heat could have been supplied when radioactive isotopes, like aluminum-26 — which is known to exist within carbonaceous chondrite meteorites — decayed and released high-energy radiation called gamma-rays. 

To test this idea, Kebukawa and her team dissolved formaldehyde and ammonia in water and then sealed the resultant solution in glass tubes. These tubes were then irradiated with gamma-rays created by the decay of the radioactive isotope cobalt-60.

The scientists discovered that this process caused the creation rate of alpha-amino acids, like alanine, glycine, alpha-aminobutyric acid and glutamic acid; as well as beta-amino acids, such as beta-alanine and beta-aminoisobutyric acid, to increase. Additionally, the team found that increasing the total dose of gamma-rays that the samples were exposed to boosted the production rate of these biomolecules. 

Considering these results and the level of gamma-ray exposure that the decay of aluminum-26 could cause, the team estimated how long this process would have taken to generate the amount of alanine and beta-alanine found in the Murchison meteorite, which landed in Australia in 1969.

They found that it would have taken between 1,000 and 100,000 years to produce the levels of these amino acids found within the Murchison meteorite. 

Kebukawa and her colleagues believe their research provides evidence that reactions driven by gamma-rays could have indeed created the amino acids that would eventually reach Earth's surface, thus providing a vital contribution to the origin of life. 

The team's research was published Wednesday (Dec. 7) in the journal ACS Central Science.

Follow us on Twitter @Spacedotcom or on Facebook.

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: community@space.com.

Robert Lea
Contributing Writer

Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.

  • rod
    "New research may have solved the puzzle of how amino acids formed within the space rocks that are thought to have seeded Earth with the building blocks of life. During the violent early epoch of the solar system, high-energy gamma-rays may have triggered chemical reactions that created the amino acids within these meteorites, which then bombarded Earth, kick-starting the origins of life, scientists propose in a new study."

    My notes. An interesting description, *the violent early epoch of the solar system*. Yes, much catastrophism is now apparent in various reports on the solar system as well as the Moon. Here is a recent example for the Moon.

    https://phys.org/news/2022-12-impact-induced-formation-microscopic-magnetite-change-.html
    ref - Sub-microscopic magnetite and metallic iron particles formed by eutectic reaction in Chang’E-5 lunar soil, https://www.nature.com/articles/s41467-022-35009-7, 23-Nov-2022.

    My observation. 2 Gyr and 3.9 Gyr ages I found in this report. Accepting the 2 Gyr age for the Chinese lunar samples, apparently the Moon still suffered from large impacts at that time. This is well into the Precambrian time scale for Earth.

    Other reports indicate much violence too.
    Publication
    https://forums.space.com/threads/giant-meteorite-strikes-in-earths-distant-history-may-have-helped-form-continents.57185/
    Such widespread and large-scale impacts during the Precambrian, should raise questions concerning how many mass extinction events of tiny life in the Precambrian took place, and how many abiogenesis events must get restarted again, again, and again to explain the fossil record we see today.
    Reply
  • rod
    This report at livescience.com too. Livescience published this report and cited the ref paper too.

    https://www.livescience.com/radioactive-meteorites-seeded-life-on-earth
    I note the ref paper link, Gamma-Ray-Induced Amino Acid Formation in Aqueous Small Bodies in the Early Solar System, 07-December-2022. The paper discusses the Murchison meteorite and states; “Although the apparent amino acid production rate (k) obtained here includes the effects of decomposition of the amino acids during the gamma-ray irradiation, the long-term stability of amino acids is worth discussing in the present context. According to the decomposition kinetics data collected in a previously published study, at room temperature, 50% of alanine is expected to decompose in aqueous solution over a period of 1.5 × 10^7 y; moreover, 99.9% of alanine is expected to decompose over ∼1.5 × 10^8 y under the same conditions. (31) The said time frames are long enough for the specified amino acids to have the opportunity to form (<10^7 y of alteration). However, the half-life of alanine was determined to decrease to ∼10^5 y at 50 °C and ∼10^3 y at 80 °C. (31) As a result, the final alanine concentration in the parent bodies should have been affected by the thermal decomposition of alanine if the alteration temperature was over several tens of degrees Celsius. In general, β-alanine is thermodynamically more stable than alanine; however, both have been found to exhibit similar stabilities under alkaline conditions. (32) Based on our findings, the very similar abundances of alanine and β-alanine observed in the Murchison meteorite (∼1.3 and ∼1.4 μg g–1, respectively) (30) despite the preferential formation of alanine over β-alanine could be attributed to the higher stability of β-alanine.” The paper conclusion stated. “Conclusions A Strecker-like reaction involving HCN, ammonia, and aldehydes (or ketones) in the presence of water was the classic scenario for α-amino acid formation in meteorite parent bodies, and a Michael addition of ammonia to unsaturated nitriles was the classic scenario for the formation of β-amino acids in the same context. (38,39) Moreover, aldehydes and ammonia can produce a variety of amino acids, including α-, β-, and γ-amino acids, (6,7,9,10) as well as hexamethylenetetramine, which easily decomposes into formaldehyde and ammonia. (8) In addition to these possibilities, gamma rays could assist the formation of amino acids in the parent bodies. Our findings point to the possibility of gamma-ray-induced amino acid formation from ubiquitous simple molecules such as formaldehyde and ammonia in the presence of water inside small bodies during the early stages of the formation of the Solar System. The gamma-ray-induced production of amino acids could be a novel prebiotic amino acid formation pathway that could have contributed to the origins of life on early Earth, as building blocks of life were delivered through the fall of meteorites.”

    My observation. This is catastrophic bombardment and impacts used to explain the origin of water and life arising on Earth. Abiogenesis must create life from non-living matter (according to science), and likely during intense bombardment periods. Abiogenesis must create life from non-living matter during the catastrophic and violent bombardments Earth experienced through Precambrian, some heavy impacts continuing from 4.5 Gyr to 2 Gyr in various reports. As I stated in post #2, "Such widespread and large-scale impacts during the Precambrian, should raise questions concerning how many mass extinction events of tiny life in the Precambrian took place, and how many abiogenesis events must get restarted again, again, and again to explain the fossil record we see today."
    Reply