The isotopic properties of a compound can be used to study its origin and evolution, and this technology can be applied to the study of the origin of water on Earth. So what do we know about the water on our planet? First, there is no place other than the earth In the solar system Or you know for sure that there is liquid water beyond that.

We know that there is ice made of water On the moon In Europe and Enceladus (moons of Jupiter and Saturn, respectively), or in comets such as 67P / Churyamov-Gerasimenko. We also know about the presence of water vapor in cryovolcanoes on these moons and interstellar mediums, especially near star-forming regions. So is all this water the same – does it have the same isotopic structure?

When that happens, there is a paradox in the origin Earth’s water. Despite the fact that water is one of the most abundant compounds in the stellar regions where the Sun and Earth evolved, the environment in which the Sun and Earth were created was quite dry. Indeed, according to scientific modeling, Earth-like rocky planets appeared in an area of ​​the Solar System close to the Sun. Here, the high temperature prevented the formation of an atmosphere in which water could expand beyond a gaseous state. Thus, the formation of water escaped the planet’s gravity.

There is also a paradox in the presence of carbon, another basic element of life on Earth. Carbon is the fourth most abundant element in the universe after hydrogen, helium and oxygen, and the second most abundant element in our body (about 20% of our body mass is carbon). However, the amount of carbon on Earth is 10 times less than in the universe.

Yet what is the relevance of carbon here?

A small fraction (approximately 5%) of the meteorites that reach our planet today are high in carbon. They are called ‘carbonaceous chondrites’ and contain high levels of water. This means that in the early days of the Solar System, water, methane, or ammonia must have formed in areas far from the Sun, beyond what was already known as the ‘freezing line’, where temperatures allowed for the formation of ice. . This is one of the reasons why water is thought to have reached the Earth through the bombardment of these meteorites at a time when it was already considerably frozen after the formation of the Earth.

Of course, another question is when the water may have arrived. There is evidence of its existence on our planet 4.4 billion years ago, and 100 million years after its formation, our planet’s surface temperature must have been cold enough to freeze water. This evidence is based on the study of certain minerals, such as zircon, which are highly resistant to geological changes and atmospheric activity, thus providing little or no information about the evolution or origin of the earth’s water.

The study of the ‘isotopic abundance’ of water contained in carbonaceous chondrites, although at least as old as the Solar System, has similar effects to that of Earth’s water. In particular, the ratio of these isotopes to Earth’s water is very similar to that of Jupiter’s adjacent concentrates, some of which are commonly studied for deuterium and protein levels extracted from the asteroid Vesta. More to the outside (e.g., from the outside in comets Of the solar system), The abundance of deuterium is so high that it occurs in an area known as the Oort cloud.

So what does Jupiter and the Moon have to do with the whole story of water on Earth? In the case of Jupiter, Jupiter’s influence comes from its intense gravitational pull in the Solar System, which shakes the orbits of a group of asteroids. Some evolutionary models suggest that at some point in the history of the Solar System, Jupiter may not have had the same orbit as it does today – instead, it may have been closer to the Sun before moving to its current position. This orbit of Jupiter would cause objects in the orbit to be swept away, which would launch en masse into the inner orbit closer to the Sun and thus land. This is known as the ‘Late Massive Bombardment’ – for example, the density of meteorite falls on the Moon about 3.9 billion years ago.

This is where the role of the moon appears. To understand this, we must return to the study of isotopes, but this time we are talking about molybdenum, a very rare element. Molybdenum is a metal with 42 protons (for comparison iron has 26) and dozens of isotopes. It turns out that the relative abundance of these isotopes on Earth occurs in the midst of the observed abundance of carbonaceous concentrates and concretes from distant parts of the Solar System.

It is not surprising to think that molybdenum is denser than iron (a small cube about the size of a centimeter of metal weighs 10 grams, seven grams if it is iron and one gram if it is water), and that most of the iron on our planet, molybdenum, which landed at the beginning of history, sank to the core of the earth. Surface molybdenum on the crust or upper mantle may have a more recent origin, and its isotopic structure points to areas rich in carbon and water. The timeline is linking the arrival of molybdenum and water to the impact of the protoplanet Thea, which caused the formation of the Moon after it collided with Earth 4.5 billion years ago. According to these ‘molybdenic studies’, Thea is not from a region of rocky planets, but from a region of gaseous planets (Jupiter, Saturn) and / or water ice planets (Uranus, Neptune). .

Thus, although the evidence is not conclusive, a planetary catastrophe caused by Thea, with its consequent formation of the Moon, perhaps mediated by Jupiter, had a fundamental influence on the appearance of life for a number of reasons. It accounts for most of the water that exists on our planet today.

Similarly, when we are thirsty, we may think that our lives are more connected to the stars than we think and that they are the result of the collision of giants in addition to star dust.