Lightning, volcanoes, or impacts? How Earth gained its organic molecules revealed

A new study demonstrates how meteoritic and volcanic particles promote 'origin of life' reactions.
Sade Agard
Concept image of 'origin of life' molecules coming from space
Concept image of 'origin of life' molecules coming from space


Around 4.4 billion years ago, chemical reactions caused by iron-rich particles from meteors or volcanic eruptions on Earth may have created the precursors necessary for the origin of life, according to a study published in Scientific Reports.

Significantly, the findings help to bring to rest the debate as to whether life's building blocks were triggered by processes within early Earth or from space, as it demonstrates that both were significant.

Like the Miller-Urey experiment, the study recreates early Earth

Previous research has put forward two potential origins for the building blocks of organic molecules like hydrocarbons, aldehydes, and alcohols. These origins consist of the delivery of these molecules by asteroids and comets.

Alternatively, they could have been created through reactions taking place in the early Earth's atmosphere and oceans, such as lightning and volcanic activity. Due to insufficient data, the question of which of these two sources played a more substantial role in the formation of life's essential components has been a topic of ongoing debate – until now.

Lightning, volcanoes, or impacts? How Earth gained its organic molecules revealed
Formation of prebiotic key organic matter from CO2 by catalysis with meteoritic and volcanic particles.

In the new study, Oliver Trapp and colleagues aimed to explore whether meteorite or ash particles deposited on volcanic islands may have aided in atmospheric carbon dioxide's conversion to the precursors. 

By adding carbon dioxide gas to a heated and pressurized system (an autoclave) and varying the pressure and temperature, they could simulate various conditions that previous research has suggested may have existed on the early Earth. Pressures and temperatures ranged between nine and 45 bars and 150 and 300 degrees Celsius, respectively.

By introducing either hydrogen gas or water to the device, they simulated both wet and dry climate conditions. 

To simulate the deposition of meteorites or ash particles on volcanic islands, the team added crushed samples of iron meteorites, stony meteorites, or volcanic ash. 

They also added minerals that could have existed during the early stages of Earth's formation, commonly found in the Earth's crust, meteorites, or asteroids. Ultimately, the researchers tested different combinations of these materials in their system.

Meteoritic and volcanic particles promote 'origin of life' reactions

The team's experiments revealed that iron-rich particles from meteorites and volcanic ash could catalyze the conversion of carbon dioxide into hydrocarbons, aldehydes, and alcohols under various atmosphere and climate conditions that may have existed during the early stages of Earth's formation. 

They also observed that aldehydes and alcohols formed at lower temperatures, while hydrocarbons formed at 300 degrees Celsius.

The authors suggest that as the early Earth's atmosphere cooled, the production of alcohols and aldehydes may have increased. These compounds could have participated in further reactions, ultimately forming essential molecules such as carbohydrates, lipids, sugars, amino acids, DNA, and RNA.

Based on their observations and data from previous studies, the authors estimate that their proposed mechanism could have produced up to 600,000 tonnes of organic precursors annually across the young Earth. 

They propose that this process, in combination with other reactions in the early Earth's atmosphere and oceans, may have contributed to the origin of life on Earth.