How Did Earth Get Its Water? Scientists Now Look to ‚Hyperactive‘ Comets for Clues

New research offers insight into how much of Earth’s water came from long-ago comets.
(Image: © NASA/SOFIA/L. Cook/L. Proudfit)
Fresh observations of Comet 46P/Wirtanen, which swung by Earth in December 2018, suggest that more of Earth’s water came from comets than previous studies suggested.

By Elizabeth Howell |

How Earth got its oceans is a field of active debate. While comets are icy bodies that contain water, previous studies showed that the ratio of elements in many comets‘ ice is different than elements contained in terrestrial water. But in the absence of comet deliveries, it’s hard to say where Earth’s water came from.

„According to the standard theory, the Earth is thought to have formed from the collision of small celestial bodies known as planetesimals,“ officials from the French space agency CNRS, which participated in the research, said in a statement. „Since such bodies were poor in water, Earth’s water must have been delivered either by a larger planetesimal, or by a shower of smaller objects such as asteroids or comets.“

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