A Study Reveals How Old Water on Earth

VIVA – The origin of Earth's water is still a mystery. There are different hypotheses and theories explaining how the water got here and lots of evidence supporting it. A research article in GeoScienceWorld Elements shows that other Solar Systems have abundant water.

In our Solar System, water follows young stars as they grow and planets form. The evidence is in Earth's heavy water content, and it shows that water on Earth is 4.5 billion years old.

The article is "We Drink Good 4.5-Billion-Year-Old Water," and the authors are Cecilia Ceccarelli and Fujun Du. Ceccarelli is an Italian astronomer at the Institute for Planetary Sciences and Astrophysics in Grenoble, France. Meanwhile, Du is an astronomer at the Purple Mountain Observatory in Nanjing China, as quoted from a science alert site on December 20, 2022

Du is an astronomer at the Purple Mountain Observatory in Nanjing, China. The formation of the Solar System began with a giant molecular cloud. The cloud is mostly made up of hydrogen, the main component of water. Next came helium, oxygen, and carbon, in order of abundance.

The cloud also contains tiny grains of silicate dust and carbonaceous dust. The research takes people through the history of water in the Solar System, and this is where it starts. Out here in the cold reaches of a molecular cloud, when oxygen encounters a dust grain, it freezes and adheres to the surface.

But water isn’t water until hydrogen and oxygen combine, and the lighter hydrogen molecules in the cloud hop around on the frozen dust grains until they encounter oxygen.

Out here in the cold molecular cloud, when oxygen encounters a grain of dust, it freezes and clings to the surface. When that happens, the two react and form ice water or two types of water, plain water and heavy water containing deuterium.

Deuterium is an isotope of hydrogen called heavy hydrogen (HDO). It has one proton and one neutron in its nucleus, separating it from ordinary hydrogen, called protium.

Protium has protons but no neutrons. Both of these hydrogen isotopes are stable and persist to this day. Both can combine with oxygen to form water.

Moreover, when the ice water forms a coat on the dust grains, the authors call this the cold phase, the first step in the process they describe in their article. Gravity begins to exert itself on the cloud as matter clumps in its center.

More mass falls into the center of the molecular cloud and begins to form protostars. Some of the gravity is converted into heat, and within a few astronomical units (AU) of the cloud's center, the gas and dust in the disk reach 100 Kelvin (-280 Fahrenheit).

As information, 100 Kelvin is very cold in Earth terms. But chemically, it's enough to trigger sublimation and ice phase change into water vapor. Sublimation occurs in the hot corino region, the warm envelope surrounding the cloud center. Although they also contain complex organic molecules, water is the most abundant molecule in corinos.