You don't need alien asteroids, you just need a hydrogen-rich atmosphere and liquid hot magma:
A new research model shows that Earth's oceans could have formed from interactions between a hydrogen-rich early atmosphere and oxygen within the planet's magma.
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 a paper published in Nature this week.
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.
[...] 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.
"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.
Journal Reference:
Young, E.D., Shahar, A. & Schlichting, H.E. Earth shaped by primordial H2 atmospheres. Nature 616, 306–311 (2023). https://doi.org/10.1038/s41586-023-05823-0
See also:
A Family of Comets Reopens the Debate About the Origin of Earth's Water
Primordial Water Probably From Dust, Not Comets
Related Stories
The primary method for investigating where the water on Earth comes from is by measuring the deuterium to hydrogen (D/H) ratio of water from different sources. The problem with measuring that ratio in water on Earth is that almost all water that is readily available has been recycled and mixed with materials on the Earth surface or atmosphere. Recent lava flows in Canada and Iceland brought primordial material up from deep within the Earth. Researchers measured the D/H ratio of water trapped in this material and found the D/H ratio to be lower than anything else measured apart from the Sun. This suggests that this water did not come from comets nor meteorites, but from the dust cloud from which the Earth formed (from the research paper summary):
Where did Earth's water come from? Lavas erupting on Baffin Island, Canada, tap a part of Earth's mantle isolated from convective mixing. Hallis et al. studied hydrogen isotopes in the lavas that help to "fingerprint" the origin of water from what could be a primordial reservoir. The isotope ratios for the Baffin Island basalt lavas suggest a pre-solar origin of water in Earth, probably delivered by adsorption onto dust grains.
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A family of comets reopens the debate about the origin of Earth's water
Where did the Earth's water come from? Although comets, with their icy nuclei, seem like ideal candidates, analyses have so far shown that their water differs from that in our oceans. Now, however, an international team, bringing together CNRS researchers at the Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres (Paris Observatory -- PSL/CNRS/ Sorbonne University/University of Cergy-Pontoise) and the Laboratory of Space Studies and Instrumentation in Astrophysics (Paris Observatory -- PSL/CNRS/Sorbonne University/University of Paris), has found that one family of comets, the hyperactive comets, contains water similar to terrestrial water. The study, published in the journal Astronomy & Astrophysics on May 20, 2019, is based in particular on measurements of comet 46P/Wirtanen carried out by SOFIA, NASA's Stratospheric Observatory for Infrared Astronomy.
According to the standard theory, the Earth is thought to have formed from the collision of small celestial bodies known as planetesimals. Since such bodies were poor in water, Earth's water must have been delivered either by a larger planetesimal or by a shower of smaller objects such as asteroids or comets.
To trace the source of terrestrial water, researchers study isotopic ratios1, and in particular the ratio in water of deuterium to hydrogen, known as the D/H ratio (deuterium is a heavier form of hydrogen). As a comet approaches the Sun, its ice sublimes2, forming an atmosphere of water vapour that can be analysed remotely. However, the D/H ratios of comets measured so far have generally been twice to three times that of ocean water, which implies that comets only delivered around 10% of the Earth's water.
(Score: 2, Interesting) by Anonymous Coward on Sunday April 16 2023, @07:07AM
Hmmm... That plus carbonate rock.
All the components to make water and hydrocarbons.
Maybe the dinosaurs and peat bogs were not where oil came from?
I dunno, but that came to mind immediately when I read TFA.
If that is the case, our worlds petroleum reservoirs will refill all by themselves, and the show goes on, whether or not there are any people in the theater to enjoy it.