The water you drink is 4.5 billion years old, scientists reveal

It all began with a molecular cloud
Loukia Papadopoulos
Water is essential to life on Earth..jpg
Water is essential to life on Earth.


A study in GeoScienceWorld Elements reported by ScienceAlert on Saturday has revealed how water came to be on our humble planet, and it is fascinating.

Water originated on Earth through a four-step process.

It all began with a cloud. That cloud was mostly hydrogen, water's main component, with a touch of helium, oxygen, and carbon.

The oxygen in the cloud then came into contact with a dust grain. It froze and adhered to the surface.

This led to the lighter hydrogen molecules in the cloud hopping around on the frozen dust grains until they encountered oxygen.

Through this interaction, water ice was then formed. But that's just the first step called the cold phase.

Gravity then began to work its magic on the ice, and matter began to clump in the center. As more mass fell into the center of the cloud, a protostar was born. 

Gravity turned to heat, and the gas and dust in the cloud reached 100 Kelvin (-280 Fahrenheit).

The water you drink is 4.5 billion years old, scientists reveal
Water is now abundant on Earth.

Ice water is now vapor.

This triggered sublimation transforming the ice into water vapor. This was phase two: the protostar phase.

There was plenty of water at this stage but it was all vapor. Then came step three.

In this stage, we saw the introduction of a protoplanetary disk that carried within it everything that would eventually become the solar system's planets.

At this stage, the water ice that formed in step one and was transformed into gas in step two goes back to being ice in the coldest reaches of the protoplanetary disk. Dust grains are once again covered in an icy mantle.

Now comes step four when we see the Solar System begin to resemble a more fully-formed system. Planets, asteroids, and comets, start taking shape and placing themselves in their assigned orbits. 

In these elements can now be found water in its current state. Abundant, free-floating and ready to consume.

Our planet has now been shaped in all its beautiful glory.

As old as our Universe

From this new data, we can conclude that water is 4.5 billion years old, as old as our Universe. The question to be answered now is: how much of that ancient water is present on Earth today?

The authors in the new study conclude that between 1 and 50 percent of Earth's water present today came from the initial phase of the Solar System's introduction. That might seem like a wide range, but it still offers a key insight into water's early formation.

"The water in comets and asteroids (from which the vast majority of meteorites originate) was also inherited since the beginning in large quantities. Earth likely inherited its original water predominantly from planetesimals, which are supposed to be the precursors of the asteroids and planets that formed the Earth, rather than from the comets that rained on it," write the authors in their conclusion. 

The researchers are Cecilia Ceccarelli, an astronomer at the Institute for Planetary Sciences and Astrophysics in Grenoble, France, and Fujun Du. Ceccarelli, an astronomer at the Purple Mountain Observatory in Nanjing, China.

Study abstract:

Water is crucial for the emergence and evolution of life on Earth. Recent studies of the water content in early-forming planetary systems similar to our own show that water is an abundant and ubiquitous molecule, initially synthesized on the surfaces of tiny interstellar dust grains by the hydrogenation of frozen oxygen. Water then enters a cycle of sublimation/freezing throughout the successive phases of planetary system formation, namely, hot corinos and protoplanetary disks, eventually to be incorporated into planets, asteroids, and comets. The amount of heavy water measured on Earth and in early forming planetary systems suggests that a substantial fraction of terrestrial water was inherited from the very first phases of the Solar System formation and is 4.5 billion years old.

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