New insight into the origin of water on Earth

Date:
July 17, 2020
Source:
Hokkaido University
Summary:
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.



FULL STORY ========================================================================== 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 remains a number of mysteries on our planet including the elusive
origin of water on the earth. Active studies suggested that terrestrial
water had been delivered by icy comets or meteorites containing hydrous silicates that came from outside the "snow line" -- the boundary beyond
which ice can condense due the low temperatures. 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. "Until now, much less attention has been paid to
organic matter, comparing to ices and silicates, even though there is
an abundance inside the snow line" says planetary scientist Akira Kouchi
at Hokkaido University.

In the recent study published in Scientific Reports, a group of scientists
led by Akira Kouchi demonstrates that heating of the interstellar organic matter at high temperature 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. 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.

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, chemical analysis of produced oil showed similar characteristics to the typical crude oil found beneath the earth.

"Our results show that the interstellar organic matter inside the snow
line is a potential source of water on the earth. Moreover, the abiotic
oil formation we observed suggests more extensive sources of petroleum for
the ancient Earth than previously thought," says Akira Kouchi. "Future
analyses of organic matter in samples from the asteroid Ryugu, which
the Japan's asteroid explorer Hayabusa2 will bring back later this year,
should advance our understanding of the origin of terrestrial water."

========================================================================== Story Source: Materials provided by Hokkaido_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Hideyuki Nakano, Naoki Hirakawa, Yasuhiro Matsubara, Shigeru
Yamashita,
Takuo Okuchi, Kenta Asahina, Ryo Tanaka, Noriyuki Suzuki, Hiroshi
Naraoka, Yoshinori Takano, Shogo Tachibana, Tetsuya Hama, Yasuhiro
Oba, Yuki Kimura, Naoki Watanabe, Akira Kouchi. Precometary organic
matter: A hidden reservoir of water inside the snow line. Scientific
Reports, 2020; 10 (1) DOI: 10.1038/s41598-020-64815-6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200717120158.htm

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