Challenging a common perception, a new study suggests primitive ponds may have provided a suitable environment for creating Earth’s first life forms, more so than oceans.
The findings published in the journal Geochemistry, Geophysics, Geosystems showed shallow water bodies could have held high concentrations of what many scientists believe to be a key ingredient for jump-starting life on Earth: nitrogen.
“Our overall message is, if you think the origin of life required fixed nitrogen, as many people do, then it’s tough to have the origin of life happen in the ocean,” said lead author Sukrit Ranjan from Massachusetts Institute of Technology (MIT). “It’s much easier to have that happen in a pond,” Ranjan said.
Nitrogenous oxides were likely deposited in water bodies, including oceans and ponds, as remnants of the breakdown of nitrogen in Earth’s atmosphere.
Atmospheric nitrogen comprises two nitrogen molecules, linked via a strong triple bond, that can only be broken by an extremely energetic event — namely, lightning.
Scientists believe there could have been enough lightning crackling through the early atmosphere to produce an abundance of nitrogenous oxides to fuel the origin of life in the ocean.
But the new study found that ultraviolet light from the Sun and dissolved iron sloughed off from primitive oceanic rocks could have destroyed a significant portion of nitrogenous oxides in the ocean, sending the compounds back into the atmosphere as nitrogen.
In the ocean, ultraviolet light and dissolved iron would have made nitrogenous oxides far less available for synthesising living organisms.
In shallow ponds, however, life would have had a better chance to grow, mainly because ponds have much less volume over which compounds can be diluted. As a result, nitrogenous oxides would have built up to much higher concentrations, the study said.