New Insight Into the Origin of Water on Earth


Water (image: via Unsplash)

Scientists have found the interstellar organic matter could produce an abundant supply of water by heating, suggesting that organic matter could be the source of terrestrial water.

There remain a number of mysteries on our planet, including the elusive origin of water on the Earth. Active studies suggested that terrestrial water was delivered by icy comets or meteorites containing hydrous silicates that came from outside the “snow line” — the boundary beyond which ice can condense due to the low temperatures.

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The interstellar organic matter analog producing water droplets and oil as the heating temperature rose. At 102℃, analog of organic matter was uniform. At 350℃, water droplets were clearly seen. At 400℃, black oil was evidently produced. (Image: Hideyuki Nakano et al. via Scientific Reports, May 8, 2020)

More recent studies, however, have provided observations opposing to cometary origin theory, yet still failing to suggest plausible substitutions for the source of terrestrial water. Planetary scientist Akira Kouchi at Hokkaido University said:

In the current study published in Scientific Reports, a group of scientists led by Akira Kouchi demonstrates that heating of the interstellar organic matter at high temperatures could yield abundant water and oil. This suggests that water could be produced inside the snow line, without any contribution of comets or meteorites delivered from outside the snow line.

As a first step, the researchers made an analog of organic matter in interstellar molecular clouds using chemical reagents. To make the analog, they referred to analytical data of interstellar organics made by irradiating UV on a mixture containing H2O, CO, and NH3, which mimicked its natural synthetic process.

After heating at 400℃, the analog of interstellar organic matter clearly separated into two layers of oil (black) and water (yellowish transparent) (a: before heating, b: after heating at 400℃). (Image: Hideyuki Nakano et al. via Scientific Reports, May 8, 2020)

Then, they gradually heated the organic matter analog from 24 to 400℃ under a pressured condition in a diamond anvil cell. The sample was uniform until 100℃, but was separated into two phases at 200℃. At approximately 350℃, the formation of water droplets became evident and the sizes of the droplets increased as the temperature rose. At 400℃, in addition to water droplets, black oil was produced.

Akira Kouchi (Image: Hokkaido University)
Akira Kouchi (Image: Hokkaido University)

The group conducted similar experiments with larger amounts of organic matter, which also yielded water and oil. Their analysis of absorption spectra revealed that the main component of the aqueous product was pure water. Additionally, a chemical analysis of the produced oil showed similar characteristics to the typical crude oil found beneath the Earth. Akira Kouchi said:

Provided by: Hokkaido University [Note: Materials may be edited for content and length.]

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