Expert: C. Robert Reszka, Jr. - 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
Hi Steve,
Interesting question.  All the water, or most of it, that is on the Earth today was here since the Earth cooled, around 4 billion years or so.  When Earth was forming it was a molten mass but there is always water, in it's molecular form (H2O#.  As the magma cooled the water condensed out as vapor.  The escape velocity for our Earth #about 7 miles/sec) is too great for the water molecules to drift off into space so they stay here.  They formed clouds and then rain.  Rain formed oceans and seas.  The water condensed out again and the process continues to this day.  It's called the "Water Cycle".  Here's a great site put out by the United States Geological Survey:

http://ga.water.usgs.gov/edu/watercyclesummary.html

I think the program you were watching was probably talking about molecular water.  There is molecular water throughout the cosmos.  There is even the signature of molecular water found in the chromatograph analysis of stellar light from the center of our galaxy.  So it stands to reason that you can find some on meteors and asteroids.  Also, meteors are just chunks of broken planets.  he same processes that went into making their parent planet may have been the same ones that created ours.  So there would be molecular water trapped in them as well.  When the Earth was forming it was bombarded with hoards of asteroids and meteors.  All of them probably carried some molecular water which got incorporated into the body of our Earth.  Remember that this is NOT liquid water as we know it.  It is just a very stable molecule.  When you get a lot of them together you get water as we think of it.

So it might be, probably is, a combination of processes that got the water here in the first place.  Meteoric bombardment and insitu water in the magma.  One other thing; comets are just big ice balls.  Many have hit our Earth in its time so they probably added to water.  

Hope this helps.
Bob