Friday, October 3, 2014

Water on Earth is older than the Sun




If NPR can have Science Friday, then why can't ESE?

For the science class I teach, we had a lecture on water and our need to conserve it as a resource.  The professor giving the talk, a fellow fan of Iron Maiden, opened his presentation with Maiden's "Rime of the Ancient Mariner." In song, it basically recapitulates the Samuel Taylor Coleridge poem of the same name, including the famous line:

"Water, water everywhere, nor any drop to drink."

Turns out that's truer than we knew.

This bit from Discover really got my attention: Earth's water is older than the Sun.

That might seem counter-intuitive.  After all, what in our solar system could be older than the Sun?  As it turns out, over half of the water on Earth was brought here in the form of interstellar ice.  This ice floated about in the void before our Sun formed.  This means that water didn't form after Earth did but rather was drawn in during the proto-planetary stages.  By extension, it confirms a belief that water is actually fairly common in the universe, even if just in the form of ice.

As I usually get, someone invariably greets information like this with "But how do they know?"  I guess it's not such an unreasonable query.  The "how" of things, as described in the linked article, is via deuterium.  Deuterium, often called "heavy hydrogen" as it carries an extra neutron, has a higher ratio to hydrogen in frozen water found in space.  This was determined by examining ice found on asteroids and comets.  As the article states:

"But, confounding the matter, deuterium levels in the solar system’s water have also been rising ever since the sun formed. So to determine if the sun alone could produce today’s levels of the isotope, researchers built a computer model that essentially wound back the clock to the beginning of the solar system and assumed no inherited deuterium.
However, the model system was incapable of producing deuterium to hydrogen ratios that were as high as those found in our solar system. Therefore, researchers estimate, 30 to 50 percent of our solar system’s water was already a part of the ancient molecular cloud that spawned the Sun and planets. They published their findings today in the journal Science."

Assuming that the formation of our solar system is a typical model of what happens elsewhere, it might be extrapolated that the drawing in of interstellar ice is typical of the process as well.  Granted, that's an assumption and there could be any number of variations, but that's how it goes.  Sort of like further assumptions we make regarding water.  "Where there's water, there's life" is how science sees it.  Therefore if water is common, life should be as well. Yet I'd speculate that life could form without the need for water as there is just so much we don't know.

Just face it.  There's intelligent life elsewhere.




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1 comment:

  1. On G+, Toby said: "Makes total sense. It would have to."

    I guess I was just surprised by the ratio, meaning the amount of water that came from interstellar space.

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