Much of the life processes on Earth depend on the sun, so it comes as a surprise to many when new research findings suggest that some of the water in the Earth's oceans is actually older than the solar system's sun. The discovery could have implications on understanding how planetary systems form.

For the new study "The ancient heritage of water ice in the solar system," which was published in the journal Science on Sept. 26, a group of scientists looked at the history of water ice in the solar system by examining the ratio of hydrogen to its heavier isotope deuterium, which is also known as "heavy hydrogen" due to its extra neutron.

The proportion of hydrogen with regard to deuterium in water molecules can give scientists clues about the condition on how water molecules were formed, such as whether the water ices formed before or during the birth of the solar system. Interstellar water-ice, for instance, contains a high ratio of deuterium to hydrogen.

"Water throughout the solar system exhibits deuterium-to-hydrogen enrichments, a fossil relic of low-temperature, ion-derived chemistry within either (i) the parent molecular cloud or (ii) the solar nebula protoplanetary disk," the researchers wrote.

Using computer models that compare the ratios of deuterium over time, the researchers found that water in the Earth's oceans, comets and meteorite samples contained levels of heavy hydrogen that could only be attributed to interstellar origins, which suggests that some of the water on Earth and the solar system existed before the sun was formed.

"The implication of these findings is that some of the solar system's water must have been inherited from the sun's birth environment, and thus predate the sun itself," said study researcher Ilsedore Cleeves, from the University of Michigan. "If our solar system's formation was typical, this implies that water is a common ingredient during the formation of all planetary systems."

Study researcher Conel Alexander, from the Department of Terrestrial Magnetism at the Carnegie Institution of Washington, said that a significant part of the solar system's water, a crucial ingredient for supporting life, is older than the sun and this suggests that interstellar ices may possibly exist in all of young planetary systems.

"If water in the early solar system was primarily inherited as ice from interstellar space, then it is likely that similar ices, along with the prebiotic organic matter that they contain, are abundant in most or all protoplanetary disks around forming stars," Alexander said.