Expert: Dr Thomas Bell - 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
Steve,

In the early days of this solar system, comets and asteroids collided with each other and pelted anything with enough gravitational force to draw them in including our young planet.  The densely cratered surface of the moon preserves a graphic record of these violent events.

Asteroids are composed of rocky material.  Comets are composed of various kinds of ice and dust.  Scientists think that much of the water on Earth arrived during this early bombardment in the form of cometary ice.  When this phase of 'planet building' ended, Earth had about as much water as it does today.  Most of that water is in circulation in the shallow crust, oceans, and atmosphere.  Water tied up in mineral structures deep in the crust is called juvenile water and as the crust is recycled, some of this juvenile water is released.

Your question is where did any of the water in the solar system come from and is more water being created today?  As most of us know, water is composed of hydrogen and oxygen.  In water, these atoms are very tightly bonded together and have a great affinity for each other.  In the very earliest period of the history of this solar system, a 'chemical soup' of matter formed a spiraling cloud of gas.  As that cloud became more dense, the matter began to condense into the gases, minerals, metals, and liquids we are familiar with.  These formed the building blocks of the Sun, planets, comets, and asteroids.  While new water is still being formed in our solar system, it is most likely taking place on the very edges of the solar system.

Here are some interesting references to water and comets:

http://www.sciencedaily.com/releases/2009/07/090730141658.htm
http://saturn.astrobio.net/pressrelease/141/a-taste-for-comet-water
http://www.waterencyclopedia.com/Ce-Cr/Comets-and-Meteorites-Water-in.html
http://www.mps.mpg.de/projects/herschel/HssO/index.htm
http://stardate.org/resources/ssguide/comets.html
http://www.gsfc.nasa.gov/gsfc/spacesci/origins/linearwater/linearwater.htm