The water sloshing in Earth’s oceans and coursing through its canyons may have been with the planet since it first started taking shape, new research suggests.
The origin of Earth’s water has long been a topic of considerable discussion and debate. Some scientists hold that the wet stuff is mostly primordial, dating back to the mountain-size building blocks that coalesced to form our planetabout 4.5 billion years ago.
But others think Earth was born very dry and that it took sustained bombardment by sopping-wet asteroids and comets long ago to dampen the planet to its present state. (By the way, modern-day Earth isn’t as soggy as you may think: Though water covers 70 percent of Earth’s surface, the stuff makes up just 0.05 percent or so of our planet’s mass.) [Earth Quiz: Do You Really Know Your Planet?]
The new results should hearten the primordialists. In two new modeling studies, researchers determined that tiny grains of dust swirling around the newborn sun in the region where Earth eventually formed could have held enough water to explain the amount on the planet today.
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