Earth's water might have come from ancient space rocks, meteorite discovery suggests 

 Scientists have found fingerprints of water in ancient meteorites reminiscent of the planetesimals that formed Earth. 

https://cdn.mos.cms.futurecdn.net/v4nxwCpBcRLaT8aTDdkRjY.jpg

https://www.space.com/water-on-earth-planetesimals-planetary-formation-elements-crucial-for-life