Earth's water is older than the Sun: study

A significant fraction of our Solar System's water is older than the Sun, which indicates that abundant, organic-rich interstellar ices should probably be found in all young planetary systems, astronomers say.
Water was crucial to the rise of life on Earth and is also important to evaluating the possibility of life on other planets.
Identifying the original source of Earth's water is key to understanding how life-fostering environments come into being and how likely they are to be found elsewhere.
New work from a team including Carnegie Institution for Science's Conel Alexander found that much of our Solar System's water likely originated as ices that formed in interstellar space.

Water is found throughout our Solar System. Not just on Earth, but on icy comets and moons, and in the shadowed basins of Mercury. Water has been found included in mineral samples from meteorites, the Moon, and Mars, researchers said.
Comets and asteroids in particular, being primitive objects, provide a natural "time capsule" of the conditions during the early days of our Solar System.

Their ices can tell scientists about the ice that encircled the Sun after its birth, the origin of which was an unanswered question until now.
In its youth, the Sun was surrounded by a protoplanetary disk, the so-called solar nebula, from which the planets were born.

But it was unclear to researchers whether the ice in this disk originated from the Sun's own parental interstellar molecular cloud, from which it was created, or whether this interstellar water had been destroyed and was re-formed by the chemical reactions taking place in the solar nebula.
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.
"But if the early Solar System's water was largely the result of local chemical processing during the Sun's birth, then it is possible that the abundance of water varies considerably in forming planetary systems, which would obviously have implications for the potential for the emergence of life elsewhere," said Alexander.

In studying the history of our Solar System's ices, the team - led by L Ilsedore Cleeves from the University of Michigan - focused on hydrogen and its heavier isotope deuterium.
Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons. The difference in masses between isotopes results in subtle differences in their behaviour during chemical reactions.
As a result, the ratio of hydrogen to deuterium in water molecules can tell scientists about the conditions under which the molecules formed.
The research was published in the journal Science.