Does water on Earth come from Comet?

Question

We know comet contains lot of water ice. When comet come near the Sun. It's ice water vaporized by Sun heat and ejected into space around orbit earth.
Those water later got attracted by Earth gravity and gradually fall to the ground of Earth and fill the ocean.
If this theory is true, that means our ocean level will rise gradually not only because of global warming but also because of water added from the comets.
Does this means in next few thousand years, some cities will be submerse by the rising sea water?

quantumclaustrophobe · Answer

That was a leading theory until about 10 years ago;  now, it's thought that the structure of Earth *had* a lot of water in it during formation. While probably comets delivered water also, for our oceans to be as massive as they are - comets would only be part of the solution. 
These days, we live in a middle-aged solar system, where most the cometary and rocky debris that built and shaped the planets has been absorbed;  There's still a lot out there - and, we *do* get clobbered with big pieces on occasion - but it's thought not much more will be added to Earth.

Any rising sea water in the future will likely be due to our melting polar ice caps, not from extraterrestrial sources...

Ray;mond · Answer

Likely most of the water on Earth's surface and in the mantel and crust came from comets, asteroids and planetoids. Possibly below surface water is about 99% of the total. The amount of surface water has changed very little in recent centuries.

Biff · Answer

no-it would have taken 1000's of comets worth of ice

realdolby · Answer

Most likely as Earth was cooling the heat entered the atmosphere then fell as rain,unable to escape into space.

poornakumar b · Answer

I think it was born here on Earth surface; there are enough resources on Earth for that.

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Does water on Earth come from Comet?

5 Answers