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Forming an Ocean
When you look at the ocean, it's hard to imagine the body of water that sways differently. But, according to a team of researchers, part of the H 2 O that covered much of the surface of our planet was once very different: a reservoir of hydrogen in our nascent solar nebula. It is only on Earth that this hydrogen has been mixed with oxygen to create the aquatic world we know today.
A number of theories surround the formation of the global ocean of the Earth. Comets, which contain a lot of ice, could have fed some of the water of our planet; Asteroids, while retaining less water, could also have contributed to Earth's supply. "But there is another way of thinking about water sources in the solar system's training days," said Steven Desch, a scientist on this team and a professor of astrophysics at the school. Exploration of the Earth and Space University of Arizona State University (ASU). A declaration. "Because water is hydrogen plus oxygen and oxygen is abundant, any source of hydrogen could have been at the origin of it. water of the Earth, "said Desch.
Dust and Cosmic Gases
Hydrogen was one of the main ingredients of the solar nebula, or gases and dusts that formed the Sun and the planets of our solar system.
When planets were formed, the hydrogen of the solar nebula was incorporated into their interiors. Desch and his team discovered that while most remained stuck below, some could have been combined with oxygen from other Earth materials to create the global ocean. of our planet.
Thus, the search for hydrogen in the interior of the Earth would give scientists an idea of whether there was enough room during the formation of the planet for having contributed to the formation of water in our oceans.
To study this theory, the team measured the ratio between the number of regular hydrogen atoms (H) and "heavy" hydrogen (also called deuterium). , or D) on Earth – the D / H ratio. The global ocean water dissolved in its mantle has a D / H ratio of about 150 parts per million (ppm). The water of the asteroids has a D / H of about 140 ppm and comets water ranges from 150 ppm to 300 ppm. This makes asteroids (because the D / H of cometary water is much higher) a candidate more likely than comets.
Because the D / H of hydrogen in the solar nebula was very low – 21 ppm – the researchers had previously discounted it as a source. According to Jun Wu, senior author and research badistant professor at SESE and the ASU School of Molecular Sciences, this might not be entirely correct. The hydrogen that was deposited in the Earth at the beginning may have been subjected to a series of geochemical processes that significantly increased the heavy hydrogen it contained, resulting in the D / H ratio that we see today. If that was the case, it could have been another source of water from the Earth.
To find out, the team created a computer model of the first terrestrial mantle and added it to hydrogen to see what happened to it.
In addition to computer modeling. , the team took samples of rocks from the mantle. "We calculated the amount of dissolved hydrogen in the bodies of these bodies that could have been in their nucleus. We then compared this to recent D / H measurements in samples taken from the deep mantle of the Earth, "said Desch.
The team discovered, from dissolved hydrogen, that Earth conceals about two oceans of water in its mantle. and about four to five in its nucleus. According to estimates, about one in every 100 water molecules from the Earth comes from the solar nebula. Much of the rest comes from asteroids and other comets.
The team published this book on October 9 in the Journal of Geophysical Research .
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