The earth’s oceans can return to the planet of birth

This artist illustration shows a very young star surrounded by a disk of gas and dust, the raw materials from which rocky planets such as the Earth forms.


The water sloshed in the earth’s oceans and the canyons may have been with the planet since it first started taking shape, new research suggests.

The origin of the Earth, the water has long been a subject of much discussion and debate. Some scientists think that the wet stuff is mostly original, dating from the mountain-size blocks is merged to the form of our planetabout 4.5 billion years ago.

But others think that the Earth was born is very dry, and that the sustained bombardment by sopping wet asteroids and comets long ago temper of the planet to its current state. (By the way, modern-day of the Earth is not as cheesy as you may think: All that water covers 70 percent of the earth’s surface, the stuff makes up only 0.05 percent of our planet’s mass.) [Earth Quiz: Do You Really Know Your Planet?]

The new results should hearten the primordialists. Two new modeling studies, researchers have found that tiny grains of dust around the newborn sun in the region where the Earth eventually formed would have held enough water to explain the amount on the planet today.

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And these grains may snagged the necessary water from their surroundings, only 1 million years or so, the scientists discovered. That is fast enough that the planet-building of boulders that grew from clumping the particles may be wet enough. (If it took longer for the dust slurp water than it took for the stones to form, then it does not matter how wet the granules could get — would the Earth still dry form.)

The two new studies do not represent the last word on the origin of the Earth is water, of course; the debate will undoubtedly continue, as scientists conduct additional studies and look more and more evidence is collected of meteorites on the ground floor and the comets and asteroids in the space.

And researchers will soon be able to explore two different examples of pristine asteroid material in their laboratories here on Earth, if all goes according to plan. The japanese space probe Hayabusa2 and NASA’s OSIRIS-REx probe are planned to return samples from the asteroids Ryugu and Bennu to Earth in 2020 and 2023, respectively.

The two new studies were both submitted to the journal Astronomy & Astrophysics. It has been accepted for publication; you can read it for free on the site preprint

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