Rosetta’s study deepens Earth’s water mystery, Asteroids replace Comets

The long standing theory that comets created water here on Earth might have received its final blow thanks to the Rosetta Spacecraft. The craft which has been orbiting comet 67P since August – and even landed a lander on the comet earlier in the fall – pointed out that the water that is here on Earth today, or was initially brought to Earth – likely came from a different source than scientists first believed. Scientists now believe that Earth’s water originated from asteroids instead of comets. They’re sure of this now thanks to the data that has been received from the Rosetta spacecraft.

Rosetta is currently orbiting around comet 67P, and has been doing so since August. Earlier this fall Rosetta even landed Philae – a lander on the comet. However, scientists are now leaning toward the method of thinking that “terrestrial water was probably brought by asteroids” as Kathrin Altwegg pointed out of the Rosetta study. She went on to point out that it was “more likely” the source of the water here on Earth “than comets.”


Originally, scientists did believe that the comet bombardment that happened 3.8 billion years ago was the main cause for the terrestrial water that filled Earth up. However, for some it was hard to believe that comets – which are rich with water and ice – couldn’t have been the ones to deliver water. Instead, it would appear as though asteroids were more likely the cause of the water here on Earth.

The bottom line that scientists are driving home now though is that asteroids were the actual cause. The chemical makeup fits the bill more effectively, and it would be a more likely scenario that water was brought to Earth by an asteroid – rather than a comet – since comets actually have a smaller amount of heavy water than Earth does.

Scientists actually point to the fact that asteroids were definitely not always the barren landscape that they are today. “We know asteroids have very little water, but that was probably not always the case,” according to one member of the team. The scientists believe then that in addition to being moister that given the fact that there were more of them that it would be a more-likely scenario that the water here on Earth was brought via asteroid – rather than comet.

At the end of the day though, this is just one of the many pieces of information that the Rosetta spacecraft will undoubtedly collect that gives the space community more information. And if the Philae lander is able to recharge its batteries, the results will be even more impressive.