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Galactic Inquirer

How the Earth Got its Water

23 Sep 2013, 23:35 UTC
How the Earth Got its Water
(200 words excerpt, click title or image to see full post)

Water has been identified in the most uncanny of places – as vapors in the nebulae that roam our Milky Way Galaxy, as ices in the protoplanetary disks that surround many protostars, and as liquids below the icy crusts of the Jovian moons Europa, Ganymede, and Callisto. In 2005, the Cassini spacecraft imaged geysers of liquid water erupting from the surface of Saturn’s moon Enceladus. The liquid form of water is especially important to biotic processes, as it provides an essential solvent for making the sundry hookups and energy transfers that are necessary to life.

Despite compelling evidence for water throughout our Milky Way Galaxy and within our local Solar System, the specific origin of water on Earth remains controversial. We know that the Earth formed some 4.6 billion years ago, as the primordial Solar System gravitationally congealed from the pre-planetary disk of debris that surrounded the proto-Sun. Once the Sun “turned on” its thermonuclear fires, things began to change in a big way.

The primitive Solar System was a busy chaotic place. Did Earth’s cargo of precious water come home-grown 4.6 billion years ago or was it delivered via comets during the Late Heavy Bombardment that ended 3.9 billion ...

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