Research findings recently published in Science Advances suggest much of Earth’s water may have come from comets in space.

When our planet formed about 4.6 billion years ago, it likely had some water on it. The water’s origin is a source of debate. Some believe it arrived through volcanic vapor that became rain. But new research into the makeup of certain comets’ tails seems to indicate Earth’s oceans originated as ice and minerals on asteroids and possibly comets that crashed into the planet.

Scientists from NASA report finding water on the Jupiter-family Comet 67P/Churyumov-Gerasimenko, which is the first comet to be orbited and landed on by robotic spacecraft from Earth. Researchers found water with a similar molecular structure to that comet in Earth’s oceans.

“This means there is a great opportunity to revisit our past observations and prepare for future ones so we can better account the dust effects,” said Kathleen Mandt, a planetary scientist at NASA’s Goddard Space Flight Center.

Photo by: NASA/AFP via Getty Images