Thursday , March 4 2021

Some of the Earth's water came from a hydrogen stream for a long time



Forming an ocean

When you look at the ocean, it is difficult to imagine that the body of water that is mixed is otherwise. But, says a team of researchers, some of H2What encompasses much of the surface of our planet was something very different: a hydrogen deposit in our rising solar nebula. Only on Earth has hydrogen mixed with oxygen to create the aqueous world we know today.

There are several theories about the formation of the global ocean of the Earth. Comets, which have a lot of ice, could provide some of our planet's waters; Asteroids, although they have less water, could add to the Earth's source too. "But there is another way of thinking about water sources in the days of formation of the solar system," said Steven Desch, a scientist of this team and professor of astrophysics at the School of Space and Earth Exploration (SESE) of the State University of Arizona (ASU ). a statement "Because water is hydrogen plus oxygen, and oxygen is abundant, any source of hydrogen could serve as the origin of the Earth's water," said Desch.

Cosmic dust and gas

Hydrogen gas was one of the main ingredients in the solar nebula, or the gases and dust that formed the Sun and the planets in our solar system.

When the planets were formed, the hydrogen of the solar nebula was incorporated into their interiors. While most are still blocked below, some of them could be combined with oxygen from other materials on Earth and continue to create the global ocean of our planet, Desch and his team found themselves.

So, looking for hydrogen inside the Earth, it would give the scientists an idea if there was enough time during the formation of the planet to contribute to water in our oceans.

To investigate this theory, the team measured the ratio of regular hydrogen atoms (H) to "heavy" hydrogen (also called deuterium, or D) on Earth – the ratio D / H. The water from the global ocean of the Earth and which is Dissolved in its mantle has a D / H ratio of about 150 parts per million (ppm). Asteroid water has a D / H of about 140 ppm and comet water ranges from 150 ppm to 300 ppm. This makes asteroids (because the D / H of cometary water is much larger) a candidate more likely than the comets.

Because the hydrogen D / H in the solar nebula was very low (21 ppm), researchers previously discounted as a source. Doing this may not be very correct, says Jun Wu, lead author and assistant research professor at SESE and at the School of Molecular Sciences of ASU. The hydrogen that expected the advance Earth could go through a series of geochemical processes that greatly increased the amount of heavy hydrogen that it contained, resulting in the D / H ratio we see today. If so, it could be another source of the Earth's water.

To find out, the team created a computer model of the mantle of Earth's onset and added in hydrogen to see what happened to him.

In addition to the computer model, the team took samples of mantle rocks. "We calculated what the hydrogen dissolved in the mantles of the bodies could end up in its nuclei. Then we compared this with the recent measurements of the D / H ratio in samples of the Earth's deep mantle," said Desch.

The team found, on the basis of dissolved hydrogen, that the Earth hides the water value of the two oceans in its mantle and about four to five in its nucleus. Near one of the 100 Earth molecules of water came from the solar nebula, they estimate. Much of the rest comes from asteroids and some of the comets.

The team posted this work on October 9th at Journal of Geophysical Research.


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