we explain in a Previous article Isotopic properties of a compound can be used to study its origin and evolution. And we move to another article to talk about the application of this technique in studying the origin of water on our planet. Well let’s go.
What do we know about water on Earth? First of all, there is no other place in or outside the Solar System where we know for sure that there is liquid water. We know there are Frozen water on the moon and in Europe And the Enceladusthe moons of Jupiter and Saturn, respectively, or in comets such as 67P / Churyamov-Gerasimenko. We also know that there is water vapor in the frigid volcanoes on these moons and in the interstellar medium, especially near regions where stars are forming. Is all this water the same, does it have the same isotopic composition?
The problem of the origin of water on Earth is that models Formation of rocky planets (Mercury, Venus, Earth and Mars) prove that these appeared in a region of the solar system, near the king of stars, where the temperature was high enough not to allow the formation of primary atmospheres, where water can only live in a gaseous state and it is natural that Evade the gravitational influence of each planet. That is, the environment in which the Sun and Earth originated was completely dry, despite the fact that water is one of the most abundant compounds in star-forming regions.
The paradox also affects carbon, the other basis of life on Earth, which ranks fourth in all plentiful in the universe after hydrogen, helium and oxygen (with oxygen and hydrogen at the top, no wonder water is so common in the universe) and the second most abundant element by mass in the universe our body (Roughly 20% of us are carbon). But nevertheless, carbon is ten times less abundant on Earth than it is in the universe as a whole.
Why do we mix the debate about the origin of water with the debate about carbon abundance? Because a small portion, such as 5%, of the meteorites that reach our planet today have a high carbon abundance, they are called carbonaceous chondritesInterestingly enough, it has a high water content as well. This means that it must have formed in regions very far from the sun, beyond the asteroid belt between Mars and Jupiter, beyond what is known as Freezing line, where temperatures were already well below what allowed the formation of water, methane, or ammonia ice in the early solar system. This is one of the reasons why the Earth’s waters can be considered to have arrived by bombardment of this type of meteorite at a period when the Earth had already cooled significantly since its formation.
Another question is how long can the water reach. There is evidence of water on our planet 4.4 billion years ago, more than 100 million years after its formation, when the surface temperature of our planet was cold enough for water to freeze. This guide is based on the study of certain minerals such as zirconwhich resists geological changes and atmospheric action well, so they give us information about the origins and not so much about the evolution of water on Earth.
Studying the isotopic abundance of water found in carbonaceous chondrites, at least in some, which are as old as the solar system itself, yields results very similar to those on Earth. Specifically, the quantity Deuterium vs. Protium, which is quite similar to chondrites from the vicinity of Jupiter, some of which are ripped from the asteroid Vesta (how do you know a meteorite comes from Vesta? That’s another story). Moreover, for example, in Kites Coming from the far reaches of the solar system, in what is known as the Oort cloud, the abundance of deuterium is much higher.
So what do Jupiter and the moon have to do with this whole story of water on Earth? In the case of Jupiter, its effect on matter may come from its intense gravitational influence in the solar system, which disturbs the orbits of many asteroids. At some point in the history of the solar system, some evolutionary models established that Jupiter could not have the same orbit as it does today, and could be closer to the sun and then migrate to its current position. This journey of Jupiter would have caused it to sweep away objects along its path, which could have been collectively thrown toward the inner orbits closest to the Sun, thus hitting Earth. This is what is known as Late heavy bombardment, which has evidence of a concentration of meteor impacts on the Moon about 3.9 billion years ago. But it is not entirely clear that the concentration we detected may be due to the fact that we have not collected lunar samples from more than several places, and we hope that efforts To return to the moon overcome these limitations. In any case, it appears that there was already water before this potential event, so there must have been a partly prior origin for much of the terrestrial oceans.
Here the role of the moon appears. To understand it, we return to the power of isotope study, which serves us as if it were a genetic study. But this time we are talking about a much rarer item, which is molybdenum, a metal with 42 protons (for comparison, iron has 26) of which dozens of isotopes are known. It turns out that the relative abundance of these isotopes on Earth lies in the middle of the observed abundance of carbonaceous chondrites and chondrites from the distant reaches of the Solar System. Considering that molybdenum is more dense than iron (a small cube with a side one centimeter side weighs 10g, compared to 7g if it was iron and 1g if it was water), and that most of the iron on our planet is in the core, it wouldn’t be surprising that We believe that the molybdenum that reached Earth at the beginning of its history sank and ended up in the Earth’s core. Surface molybdenum, in the crust or upper mantle, could have a more recent origin, and its isotopic composition indicates regions where there is a lot of carbon and water. Times correlate the access of molybdenum and water with Thea تأثير effect, which is the protoplanet that could have caused the formation of the Moon after it collided with the Earth 4.5 billion years ago and mixed much of its material with the Earth’s mantle. According to these “molybdenum studies”, Theia would be a planet that does not come from the region of rocky planets, but from the region of gaseous planets (Jupiter, Saturn) and / or icy planets (Uranus and Neptune) filled with water .
Currently, the evidence is not conclusive, but it is possible that the planetary catastrophe caused by Theia, with the consequent formation of the Moon, possibly mediated by Jupiter, had a fundamental effect on the appearance of life for various reasons, including providing accounts. Most of the water on our planet today. When we are thirsty, let us think that our lives may be more related to the stars than they seem to us, and that in addition to stardust, we are the products of the struggle of the giants.
Pablo J Perez Gonzalez He is a researcher at the Center for Astrobiology of the Supreme Council for Scientific Research and the National Institute of Aerospace Technology (CAB/CSIC-INTA).
cosmic void It is a section in which our knowledge of the universe is presented in a quantitative and qualitative manner. Its purpose is to explain the importance of understanding the universe not only from a scientific point of view but also from a philosophical, social and economic point of view. The name “cosmic vacuum” refers to the fact that the universe is, for the most part, empty, with less than one atom per cubic meter, despite the fact that in our environment, paradoxically, there are quintillion atoms per cubic meter which invites us to think about our existence and the existence of life in the universe. Section consists Pablo J Perez GonzalezResearcher at the Center for Astrobiology. Patricia Sanchez Blazquez, Professor at the Complutense University of Madrid (UCM); And the Eve VillavirResearcher at the Center for Astrobiology.
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