European Space Agency (ESA) researchers have discovered that water on Earth probably originated from asteroids that hit the planet billions of years ago and not from comets.

Scientists have previously thought these comets triggered life on Earth since they carry the essential building blocks of life such as amino acids. Comets are known to be ancient relics of the solar system.

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Data collected from the Philae lander currently on Comet 67P/Churyumov-Gerasimenko says otherwise, however. Philae landed on the comet last month after the Rosetta spacecraft that carried it rendezvoused with the comet in August. This marks the first time a spacecraft has ever landed on a comet.

According to Kathrin Altwegg, the principal investigator of the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis), the team concluded that terrestrial water was probably brought by asteroids as opposed to comets after examining the chemical fingerprint and gases present in Comet 67P.

The report details all the important data gathered from the Rosetta mission, whose primary goal is to study what type of comet could have crashed into Earth that brought water four billion years ago.

Philae found water, however, but it was the wrong kind since it was composed of heavier molecules not consistent with liquid water on Earth.

Scientists took the measurements and ratio of deuterium (a hydrogen isotope) and hydrogen since these can form water when mixed with oxygen.

Altwegg said Comet 67P possesses the highest level of deuterium and hydrogen ratio in any object yet found in the solar system. This means its formation was caused by very low, frigid temperatures and suggests this could be the original material out of which the solar system was formed 4.6 billion years ago.

Altwegg adds that asteroids have a lower deuterium and hydrogen ratio more similar to liquid water on Earth.

The data from the Rosetta mission isn't complete and scientists continue to study the results. Asteroids may have brought water to Earth, however, but the planet may also have kept its original water in its poles, under the crust and in glacial ice.

This study was published in the journal, Science.

TagsRosetta Data Reveal that Water on Earth Came from Asteroids Not Comets, ESA, rosetta, philae, comet 67P, water on earth asteroids not comets rosetta