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According to recent studies, some of the water molecules in your glass were formed more than 4.5 billion years ago. That makes them far more ancient than our planet, our solar system, and our star. The unique molecular fingerprint of water on Earth and throughout the solar system can only have developed before the planets, moons, comets, and asteroids were born from the spinning disc of dust and gas, according to a study published Thursday in Science.
The researchers think that between 30 and 50 percent of all water on Earth is this primordial water. “It’s pretty amazing that a significant fraction of water on Earth predates the sun and the solar system,” said study leader and University of Michigan astronomer Ilse Cleeves. Cleeves and her coworkers conclude from this discovery that water, a necessary component of life, may be prevalent in nascent planetary systems throughout the cosmos.
It is still a mystery to scientists how water got to Earth. Our planet was created devoid of liquid or ice water because the region of the protoplanetary disc in which it originated was too hot for such substances to exist. Most scientists think comets and asteroids, which developed in a colder environment, hit Earth and deposited their frozen water. However, this idea raises even more concerns. There is the question of the origin of the water found in comets and asteroids. Chemists were called upon to help answer this question. About once in every three thousand water molecules on Earth contains a deuterium atom instead of a hydrogen atom.
Deuterium is an atom that is very similar to hydrogen except that its nucleus has two protons instead of one. (A single electron can be found in both atoms.) Since deuterium weighs twice as much as hydrogen, the water molecules formed using deuterium atoms (HDO) are referred to as “heavy water.” About one deuterium molecule for every one hundred thousand hydrogen atoms was present in the universe when our sun was formed. However, the percentage of water in the solar system is far larger.
Deuterium-rich water is impossible to produce outside of a narrow range of conditions. Extremely low temperatures and sufficient energy are required to drive the process that binds hydrogen, deuterium, and oxygen. Two conflicting theories have developed over the past several decades to explain how this heavy water came to be located in our solar system. The first is that it originated in the massive cloud of gas that gave birth to our sun and the solar system, and subsequently melted to become interstellar water ice. Researchers revealed that stellar nurseries are abundant in both heavy water and normal water (H20) throughout the cosmos.
The second idea is that the interstellar water was torn apart by the fury and intensity of star birth, and its constituent parts were reprocessed within the protoplanetary disc from which the planets and other heavenly bodies later formed. Cleeves have spent years investigating how much energy makes it through the dense, chilly discs that form planets around stars. The research was a “side project,” she explained. It dawned on us that the water in our solar system couldn’t have developed here and that it must have come from somewhere else if the amount of energy in the disc is as low as we assume.
With the use of simulations, she and her team came to the conclusion that the disc was really cold enough for heavy water to develop. However, X-rays couldn’t have penetrated the dense atmosphere, and cosmic rays would have been easily deflected by the solar winds and magnetic fields. Cleeves claimed these energies were necessary for the formation of heavy water from deuterium and oxygen. Before the gas cloud compacted into the protoplanetary disc, however, it would have been simple for cosmic rays to enter it, she said. Heavy water may have been produced with the help of those rays. Professor of cosmochemistry and planetary science at Caltech who was not involved in the study Geoff Blake stated, “People have wondered for a while how much of the water in comets is inherited and how much was made in the proto-planetary nebula.”
He said that the article proved beyond a reasonable doubt that the disk’s chemistry would have been too sluggish to form heavy water because the nascent solar wind would have blocked all cosmic rays from entering. “And if that’s true, then a lot of the water in the solar system today had to be inherited,” he added. University of Michigan astronomer and Science article co-author Ted Bergin speculated that the findings could mean that old water is abundant in newborn planetary systems across the cosmos. The majority of stars, including our own Sun, are born in water-rich stellar nurseries. It seems reasonable to assume that if interstellar water could survive the traumatic birth of our sun, it may survive the formation of other stars as well. It’s all really cold material with water, and that’s what’s given to planets when they’re born, he said.