In their study, Pizzarello and her colleagues have shown that such stellar debris such as this piece of Renazzo meteorite could have seeded the planet with the materials needed to create life.
GENEVA: Researchers have found a primitive meteorite which releases ammonia - a fundamental component needed for the formation of biological molecules - when placed under conditions similar to those found on the early Earth.
Current theories on the origin of life in the Hadean Eon (around 4500-3800 billion years ago) have been unable to account for the quantity of ammonia needed to form the molecular basics of life – yet this discovery opens the possibility that some could have been brought to the Earth from outer space.
“Essentially, the finding of ammonia on the early Earth has been kind of difficult for the enduring theory of the origins of life, so the possibility that some asteroids could have delivered large abundances of this is exciting,” said lead author and biochemistry professor Sandra Pizzarello of Arizona State University.
Ammonia and the early Earth
Nitrogen - in its reduced form, ammonia (NH3) - has long been agreed to be a vital component needed for the chemical evolution of amino acids, which are the fundamental building blocks of life. Based on geological evidence of a chemically neutral atmosphere, current theories have been unable to account for the sufficient supply of ammonia needed to create biomolecules.
“Most nitrogen on the prebiotic Earth is presumed to be locked up in relatively unreactive forms such as dinitrogen, N2 and nitrates,” explained Terence Kee, a chemist at the University of Leeds and chair of the Astrobiology Society of Britain.
The new study published in the journal Proceedings of the National Academy of Sciences, however, has provided evidence of a possible new source: an influx of ammonia-rich meteorites raining down on the surface of the early Earth.
Delivering the building blocks of life
The meteorite studied belonged to the Renazzo group (CR) - a specific type of meteorite known to be rich in organic materials. The researchers took powdered samples of the Antarctic meteorite and treated the insoluble organic components in water under conditions of high pressure and temperature (300 degrees Celcius and 100 MPa).
These conditions were chosen to simulate the hydrothermal activity which would have been present on the early Earth. Considerable volumes of ammonia were seen to be released from the hydrothermally treated meteorite.
The possibility of accidental, terrestrial, contamination was ruled out by studies of the nitrogen isotope ratio of the released ammonia - which confirmed that the gas did not come from the Earth.
