the finding substantially increases the amount of water .
astronomers have found the first comet with ocean - like water in a major boost to the theory that the celestial bodies were a significant source of water for a thirsty early earth .
but research from paul hartogh of germany 's max planck institute for solar system research and colleagues published on wednesday showed a comet called 103p hartley 2 has the same chemical composition as the earth 's oceans .
meteoritic material has roughly the same proportion of deuterium that the earth 's oceans contain , and so the assumption has been that if water arrived from elsewhere , it came from asteroids .
just a few million years after its formation , the early earth 's water that covers most of the planet today .
past analysis of water - ice from far - flung comets suggested they could have delivered no more than 10 percent of today 's oceans because the chemical " fingerprints " did not match up .
in the case of hartley 2 , researchers using infrared instruments on the hershel space observatory found that ice on the comet has a near identical image caption comet hartley 2 was also the subject of the deep impact probe study comet hartley 2 contains water came from asteroids .
clouded measure until now , all of the comets that have been measured have been so - called oort cloud objects , believed to have been formed early in the solar system 's history in the region of the
the comet hartley is seen in this undated image courtesy of nasa .