A new study suggests up to a third of Earth's ocean water was formed before the birth of the sun and sourced from deep space ice.
This could mean that other solar systems had water in the beginning too, according to a study published on Thursday in the journal Science.
The new information suggests that the ingredients for water were around before the protoplanetary disk of condensed gas that was the early stage of our solar system gave birth to the planets some 4.6 billion years ago.
"The implication of these findings is that some of the solar system's water must have been inherited from the sun's birth environment," Lauren Ilsedore Cleeves, a doctoral student at the University of Michigan and lead author of the study, said in a statement. "If our solar system's formation was typical, this implies that water is a common ingredient during the formation of all planetary systems."
The part of the protoplanetary disk that formed the Earth was too dense for radiation from space to enter. Without that energy source, water couldn't have formed, according to researchers from the University of Michigan and the Max Planck Institute for Radio Astronomy in Germany.
What scientists haven't been able to figure out is exactly how much of our water is made of interstellar ice, and how much was formed locally in the solar nebula.
To figure out that question, a team of scientists, led by Cleeves, built a model to try predicting the answer.
The model was created based on scientists' understanding of the chemical circumstances that enable the formation of "heavy" water molecules, a molecule with a deuterium atom instead of a hydrogen atom, according to the study.
One in every 3,000 water molecules on Earth has a deuterium atom instead of a standard hydrogen one. Deuterium is also known as "heavy hydrogen" because of its extra neutron. For hydrogen and deuterium to exist in their current ratios, some of the water would have had to form before the sun, researchers said according to Reuters.
This means conditions in early solar system would have made water formation impossible.
"The finding makes it quite hard for these regions in the disk to synthesize any new molecules," Cleeves told Discovery. "This was an 'aha' moment for us - without any new water creation, the only place these ices could have come from was the chemically rich interstellar gas out of which the solar system formed originally."
Primordial water makes up as much as 30 to 50 percent of Earth's water, according to the Los Angeles Times.
Cleeves said it was "remarkable" that these ices survived the formation of the solar systems. Researchers said this could be the case for other solar systems as well.
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