NOVA: Water in Small Dust Grains Can Explain Large Amounts of Water on Earth

September 11, 2018

Water trapped in dust grains from which the Earth formed can explain the current large amount of water on Earth. This is suggested by scientists from the Netherlands, Germany and the United Kingdom, based on calculations and simulations. The research will appear in two articles in the journal Astronomy & Astrophysics.

For a long time, scientists have been struggling with an explanation for the large amount of water on Earth. A first scenario states that the water is delivered by comets and asteroids that hit the Earth. According to a second scenario, the Earth was born 'wet' and the water was already present on ten-kilometer-big boulders from which the Earth was built up. However, the amount of water that these large boulders can contain, is limited.

Now, an international team of scientists has devised and calculated a variant of the boulder-with-water scenario. "Our work shows how collaboration between mineralogists, chemists, and astrophysicists helps to tackle the fundamental question on the origin of water on Earth and on other water-rich exoplanets," says Wing-Fai Thi from the Max Planck Institute for Extraterrestrial Physics (MPE), the lead author on the first paper.

The team shows that in the region where the Earth once originated, small up to mm-sized dust grains can hold enough water. The water-rich dust grains then clump together to form pebbles and eventually kilometer-big boulders. These boulders can then contain large amounts of water and they will eventually proceed to form the Earth as we know it.

The new calculations also show that the small dust grains can collect enough water in 'only' a million years to explain the amount of water on Earth. A million years fits easily in the time it takes to form the larger boulders.

“This is a new missing piece to the puzzle which links us to our progenitor cloud and Solar Nebula. Piece by piece, we hope to reveal soon our astrochemical origins!” comments Paola Caselli, who leads the Centre for Astrochemical Studies at the MPE.

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