The origins of the Earth's water are a big mystery, but we may still have a piece of the puzzle.


If the Earth did not have water, it would have no life and the universe would be sorely lacking stupid memes. But the way water has sprung on this planet has always been a perpetual mystery. The Earth did not magically appear out of the oceans covered ethereal oceans. Water has a history of origin, and scientists have never fully agreed on this story.

In a new article published in the Journal of Geophysical Research: PlanetsResearchers at Arizona State University suggest that water on Earth came from materials brought by asteroids, aided by leftover gas scattered after the formation of the sun.

This is certainly not the first time people suggest water as we know it (and drink it), it has an extraterrestrial origin. The simplest explanation has always been that all of the Earth's water came from asteroids that had an impact on Earth at the beginning of its 4.6 billion years of life. Why? Terrestrial water shares the same chemical signatures as the water present in asteroids, namely the ratio between deuterium (an isotope of heavy hydrogen) and normal hydrogen. And previous experiments have shown that, despite all the heat and energy generated by these massively powerful collisions, this water could have been preserved as it stood on the still blue planet.

Yet these theories have never been enough to fill some of the other blind spots we have about the origin of water. Hydrogen in the Earth's oceans is not necessarily the same a kind of hydrogen present in the rest of the planet – samples taken closer to the Earth's core contain extremely small quantities of deuterium, which seems to suggest that this hydrogen does not come from asteroid impacts.

"Although many models consider that it is likely that the Earth has hydrogen in the nucleus, no one has considered the extent to which this would alter the isotopic ratios of hydrogen. . " [deuterium versus hydrogen] in the coat, "states Steven Desch, a researcher at Arizona State and co-author of the new study. "The Earth had to start with an additional source of hydrogen containing less deuterium in hydrogen than the asteroids. The only possible source is the solar gas of the nebula.

The group began to take this idea more seriously, thanks to research in recent years that began to show how proto-planetary bodies could have coexisted with solar gas from the nebula (which we thought was disappearing too much). early before the formation of the planet begins) and create more opportunities for hydrogen to integrate into the deeper parts of a growing planet.

In the end, the researchers used the new framework developed to establish the most plausible scenario in the history of water: asteroids containing piles of water began to unite billions ago. years while the sun still held a solar nebula. These asteroids created what we could call planetary embryos, clashed and merged, before crushing them with enough energy to form a layer of magma outside the embryo.

At the same time, solar gas from the nebula, which includes hydrogen and other rare gas elements, began interacting with the magma to create an atmosphere. The hydrogen of the solar nebula is dissolved in the iron of the magma layer. A chemical process called isotope fractionation brought the normal hydrogen even closer to the nucleus of the embryo, while the heavier (and rarer) deuterium remained in the mantle. Smaller embryos made from other water-filled asteroids have affected the growing terrestrial fetus, until the solar system finally finds itself with the earth-sized earth that it know and adore, teeming with water.

Overall, this story confirms that most of the Earth's water comes from asteroidal sources, but also that a fraction – 0.1 to 0.2% – of the planet's oceans has been formed by hydrogen from the gas of the solar nebula.

In addition, researchers used the model to predict that the Earth had enough hydrogen to make up about eight oceans of water: a resident at the surface, two atoms of hydrogen in the mantle and enough hydrogen for five oceans sitting in the Earth's heart.

In the end, the main limitation to these results is that we work with models. There is no real way to prove that this happened.

Nevertheless, scientists can do some things to test some of the possibilities offered by this new theory. We have no idea what isotopic fractionation looks like in the type of depth and pressure that would have been detected in an ancient terrestrial embryo, but the team plans to conduct laboratory experiments to characterize this process in more detail so that the model can work better. reflect what is really happening. The team is also looking to collect and analyze more mantle samples with very low ratios of deuterium to hydrogen, which would reinforce the history of this origin.

Beyond the Earth, the major implications of the new theory relate to the livability of other worlds. "Even planets that form far from water-rich sources of asteroids can still have water," says Desch. "Not as much as the Earth, perhaps, but there is a floor of about 0.1 to 0.2 ocean of hydrogen," applies to Venus and many other exoplanets . "To the extent that the model is verified, it strongly supports the idea of ​​rapid global growth" and excites the possibility that habitable worlds are forming faster than we think. "It changes our understanding of the planets a lot."

David P. O'Brien, a researcher at the Planetary Science Institute in Tucson, Arizona, who did not participate in the study, thinks the new model is interesting enough to incorporate several different mechanisms for water. "In the past, most models have looked at these different mechanisms in isolation, trying to show how they could individually explain all of the Earth's water," he says. "This new study examines them together and shows that they were probably in service at a time … and the end result is consistent with the measured values ​​of deuterium-hydrogen and the abundances of rare gases on the Earth." O & # 39; Brien finds that what we thought we knew about the origin of water on Earth is a good demonstration that these types of processes are complex and multifaceted.

At the very least, the new document recalls that there is in space a bunch of rocks that probably harbor water chasms, and that could be decent sites for a day of drilling, baby, exercise.