Boffins rewrite the book on how Earth's oceans developed
- Reference: 1681392134
- News link: https://www.theregister.co.uk/2023/04/13/earth_ocean_theory/
- Source link:
The study from the multi-institution AETHER project also demonstrates why Earth's core is lighter than it should be, owing to the presence of gaseous hydrogen.
Edward Young, professor at the University of California Los Angeles, and colleagues propose that one of the protoplanets involved in the formation of Earth was heavier than thought. By maximizing its size to more than a fifth or third of Earth, the researchers show there would have been enough gravity to make the hydrogen-rich atmosphere hang around long enough to interact with the magma ocean, according to [1]a paper published in Nature this week.
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Prevailing theories explaining the abundance of water on Earth – oceans make up around 70 percent of the planet's surface – depend on the impacts of water-carrying asteroids.
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In an accompanying article, Sean Raymond, researcher at France's Laboratoire d'Astrophysique de Bordeaux, said: "By revising the idea that Earth's largest protoplanets were as small as Mars, Young et al have proposed a way in which hydrogen gas could have mixed into Earth's mantle before it solidified, affecting the entire planet through convection. This suggests that gaseous hydrogen is the light element responsible for the low density of Earth's core."
[5]Launching today: ESA's Juice spacecraft to probe Jupiter's moons for life signs
[6]Goddard Space Flight Center's new boss swears in on holy Pale Blue Dot
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[8]Move over, Google Earth. Caltech's here with a fresh 3D tour of Mars
Magma is made up mainly of oxygen and molten silicon. "The authors have demonstrated that early interactions between magma oceans and atmospheres represent a key ingredient in future models of how Earth was shaped," Raymond said.
The author's calculations show that interactions with atmospheric hydrogen could produce enough water to fill the current volume of our oceans three times over.
In a statement coinciding with the publication, co-author Anat Shahar, staff scientist and deputy for Research Advancement Earth and Planets Laboratory at Carnegie Science, said the inspiration for the new model came from studies of planets forming outside the solar system.
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"Exoplanet discoveries have given us a much greater appreciation of how common it is for just-formed planets to be surrounded by atmospheres that are rich in molecular hydrogen during their first several million years of growth. Eventually, these hydrogen envelopes dissipate, but they leave their fingerprints on the young planet’s composition," she said.
"This is just one possible explanation for our planet's evolution, but one that would establish an important link between Earth's formation history and the most common exoplanets that have been discovered orbiting distant stars, which are called Super-Earths and sub-Neptunes," Shahar said. ®
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[1] https://www.nature.com/articles/s41586-023-05823-0
[2] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/science&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2ZDgnJGbJ8eeA9N9dxyJttgAAABY&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[3] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/science&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44ZDgnJGbJ8eeA9N9dxyJttgAAABY&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[4] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/science&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33ZDgnJGbJ8eeA9N9dxyJttgAAABY&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[5] https://www.theregister.com/2023/04/13/esas_juice_spacecraft_jupiter/
[6] https://www.theregister.com/2023/04/12/goddard_space_flight_centers_new/
[7] https://www.theregister.com/2023/04/09/black_hole_stars/
[8] https://www.theregister.com/2023/04/08/mars_caltech_map/
[9] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/science&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44ZDgnJGbJ8eeA9N9dxyJttgAAABY&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[10] https://whitepapers.theregister.com/
The comet ice had to come from somewhere.
It's not unreasonable to suppose Earths water arriving/appearing from multiple sources.
Hot magma + hydrogen = Water is not a formula that immediately would have sprung to my mind, but it's a much more elegant theory than being pelted by comets.
Nice idea!
That's right...
...BOFFINS! Are you listening, IOP?
To this planetary physics tyro I don't understand how the "reverse electrolysis" of hyrogen and oxygen into dihydrogen monoxide would occur.
Dihydrogen monoxide? What's that? Two H ... one O, I see!! :-)
High temperature geochem is way beyond my intuition, but this seems pretty suspect to me as well. It is not like this hypothesis removes the need for a late veneer elsewhere, right?
Combination theory
Combine this with the newer theory that Earth was once a water world, that has been losing water ever since, and it starts to make sense. Eventually we wind up as Mars.
Re: Combination theory
If you are refering to the hypothesis I think you are, that water ended up in the Earth's mantle as its capacity to hold water increased. Mars is a very different planet from Earth, that ended up the way it is for different reasons: it is a smaller planet, further from the sun. This mechanism couldn't happen on mars, because Mars does not have the plate tectonics Earth does that are required to lose water to the mantle, and its water was lost long ago, likely out of its atmosphere.
Conditions in the solar system today are different today as well. Earth will boil because the sun is getting brighter. Our best understanding today is that eventually we will will probably end up a hot unlivable and wet world. The carbonate-silicate cycle will be disrupted, plants will die, animals will die, oxygen will begin to deplete on earth, the oceans will boil and we will be a wet hot (>100 C) world 900 million years or so from now.
Not at all convinced just yet, and to be honest, a single Nature paper should not convince anyone of anything important.
I am not an expert, my degree is in planetary science, but I focussed on low temperature aqueous interactions, far from magma oceans. However, I know that 1. the reasons for our current understanding of Earth's formation are complex and 2. Comets and similar bodies would be more common 4.5 billion years ago, it is not like we are saying this bombardment would happen today.
We look at many isotope systems, physical models as well as evidence from other bodies (especially the moon, which was formed from a collision that also created the modern Earth.) when we talk about the history of early and proto-earth. Little direct rock evidence exists, so a lot is uncertain or contested. Someone changing parameters in a model to show you can get a result that matches core density, oxidation state and water content would need to still show that a model like this is compatible with the many other types of information we have about early earth.
Not so elementary
"Magma is made up mainly of oxygen and molten silicon."
It would have been much more precise to say that magma is mainly silicate, oxygen and silicon combined.
I never did really buy the comet theory.