Some 30 to 50 percent of the water on Earth was created more than 4.5 billion years ago and is older than the solar system and the sun, researchers say.
Their study, published Thursday in Science, says there is a distinct chemical in the water found on Earth and throughout the solar system — a situation that could only happen if some of the water was formed before planets, moons, comets, and asteroids.
"It's pretty amazing that a significant fraction of water on Earth predates the sun and the solar system," Ilse Cleeves, an astronomer at the University of Michigan and study leader, told the Los Angeles Times.
Scientists are still trying to determine how water made it to Earth, as the protoplanetary disk in which the planet was formed was too hot for ice water or liquid to exist.
There are two theories: one is that the water came from ice that formed in the cloud of gas that formed the sun and our solar system, and the other is that the energy of a star birth split apart interstellar water, and it was reprocessed within the protoplanetary disk that would form planets.