Expert: Keith Patton - 10/25/2009

Question
Hi,

Is there a geophysical/chemical process that creates "new water" or is all water simply reprocessed previously-existing water(i.e., evaporation, rain, etc.)?

If the latter, this forces the question where did the original water come from?

I heard on a TV show that some scientists think it came from meteors that crashed into the earth billions of years ago.But this forces the question, "how did water form on the meteors and why couldn't the same process have occurred on earth?

Many thanks,

Steve

Answer
Reprocessed.  However, there is new water vapor released during volcanic eruptions, but it too could be considered reprocessed.

Hydrogen isotope ratios point more towards asteroids as a primordial source, rather than meteors.
They also think that outgassing of volitile components during the cooling of the early earth were held in the atmosphere resulting in the oceans.  

The jury is still out as neither hypothesis has been proven.

The water cycle is as you say just reprocessing water through, transpiration and evaportation then precipitation (rain, snow, hale, sleet) then runoff, infiltration and percolation.  The precipitated water becomes ground water and surface water.

80% of our drinking water comes from ground water.  The other 20% is from surface water.