Why is there water on Earth?

rod

Oct 22, 2019
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An interesting report and wrap up here. "What are the consequences of a local origin of water?
This does not tell us when the oceans appeared on Earth's surface, but we now know that Earth's water was not necessarily delivered by hydrated bodies that formed very far from the sun. However, we do not yet understand in what form(s) and by what process hydrogen was incorporated and stored in rocks of the inner solar system. The presence of hydrogen in inner solar system rocks is particularly important because it could have been a water source for the other rocky planets (Mercury, Venus, and Mars). Similar rocks could then represent a source of water for planets orbiting other suns, a condition to develop life, at least life as we know it."

Other models promote pebble accretion as the solution. The Milky Way may be swarming with planets with oceans and continents like here on Earth, https://phys.org/news/2021-02-milky-swarming-planets-oceans-continents.html, Feb-2021

https://www.sciencedaily.com/releases/2021/02/210222192839.htm, Fed-2021. "Summary: According to a new study, Earth, Venus and Mars were created from small dust particles containing ice and carbon. The discovery opens up the possibility that the Milky Way may be filled with aquatic planets."

Interesting methods for creating Earth's abundant water supply we observe and measure today in science. There is also the giant impact model using Theia to create the Moon. Various N-body simulations demonstrate that Theia *can remain stable* before hitting the proto-Earth from 30 million to one billion years after solar system formation. Theia has much to say about Earth retaining water too :).

All of the methods used so far to create Earth's abundant water supply we see today use catastrophism in the solar system in some form or another to explain Earth's abundant water supply. Catastrophic events can also create an Earth very sterile and dry today.
 
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rod

Oct 22, 2019
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Another observation that ties in nicely with water on Earth and how the water got there in origins science studies. Carbon is another critical element that is finely balanced.

See the report, From stardust to pale blue dot: Carbon's interstellar journey to Earth, https://phys.org/news/2021-04-stardust-pale-blue-dot-carbon.html

"A planet's carbon must exist in the right proportion to support life as we know it. Too much carbon, and the Earth's atmosphere would be like Venus, trapping heat from the sun and maintaining a temperature of about 880 degrees Fahrenheit. Too little carbon, and Earth would resemble Mars: an inhospitable place unable to support water-based life, with temperatures around minus 60...Most models have the carbon and other life-essential materials such as water and nitrogen going from the nebula into primitive rocky bodies, and these are then delivered to growing planets such as Earth or Mars," said Hirschmann, professor of earth and environmental sciences. "But this skips a key step, in which the planetesimals lose much of their carbon before they accrete to the planets." Hirschmann's study was recently published in Proceedings of the National Academy of Sciences. "The planet needs carbon to regulate its climate and allow life to exist, but it's a very delicate thing," Bergin said. "You don't want to have too little, but you don't want to have too much."

The paper cited is Earth’s carbon deficit caused by early loss through irreversible sublimation, https://advances.sciencemag.org/content/7/14/eabd3632, 02-April-2021. "Abstract Carbon is an essential element for life, but its behavior during Earth’s accretion is not well understood..."
 

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