Water covers more than two-thirds of the Earth's surface, but the question regarding the exact origin of the planet's water still remains unanswered.

For long, scientists have been uncertain about whether water was present since the formation of the planet or if it arrived later, perhaps deposited by comets or meteors. However, now, a new study suggests water was already present on the planet when it formed.

Researchers from Glasgow and Hawaii universities, using advanced ion-microprobe instrumentation, have found that rocks from Baffin Island in Canada provide evidence that water existed on Earth since the planet was formed, reported Phys.Org.

"Our measurements suggest that Earth had its water from the very beginning of its formation and the water originated from the proto-solar disk," said Dr Lydia Hallis, lead author of the study.

Dr. Hallis is a planetary scientist at the University of Glasgow in the United Kingdom.

The research team examined rocks from Baffin Island, Canada, which were formed from lava churned out during volcanic activity. The rocks remained untouched for millions of years.

"The Baffin Isand rocks were collected back in 1985, and scientists have had a lot of time to analyze them in the intervening years. As a result of their efforts, we know that they contain a component from Earth's deep mantle," said Dr.Hallis.

"On their way to the surface, these rocks were never affected by sedimentary input from crustal rocks, and previous research shows their source region has remained untouched since Earth's formation. Essentially, they are some of the most primitive rocks we've ever found on Earth's surface, and so the water they contain gives us an invaluable insight into Earth's early history and where its water came from."

The researchers examined minute pockets of glass inside the rocks using ion microprobe technology to detect the tiny amounts of water within, reported LiveScience.

The researchers were able to confirm where water came from within the solar system by studying the ratio of deuterium, also known as heavy hydrogen, to normal hydrogen in the water molecules, because different sources have different ratios. The range of D/H ratios found on Earth are due to hydrological cycles. Those cycles suggest that water has been present in the planet since its birth, according to Yahoo News.

"We're looking forward to further research in this area in the future," Dr. Hallis added.

The research study appears in journal Science.