New Research Proposes Asteroid Strikes as the Origin of Earth’s Water

Salt crystals, which only form in the presence of liquid water, have been discovered on an asteroid sample brought back to Earth by a Japanese mission.

Published today in Nature Astronomy, this new research provides evidence supporting the theory that all of Earth’s surface water initially came from asteroid impacts. This is because it is believed that Earth, along with Mars, Venus, and Mercury, formed near the sun where temperatures were too high for water vapor to condense into liquid.

Previously, it was believed that S-type (stony or silicate) asteroids, such as asteroid Itokawa – the source of this sample brought back in 2010 by the Hayabusa mission – did not contain water-bearing minerals.

However, since most asteroids in the inner solar system are S-types, it is now possible that there are many wet asteroids in existence.

Scientists at the University of Arizona’s Lunar and Planetary Laboratory discovered traces of sodium chloride (table salt) on the sample.

“It has long been thought that ordinary chondrites are unlikely sources of water on Earth,” said Shaofan Che, lead author and director of the Kuiper Materials Imaging & Characterization Facility. Che ruled out any possible contamination sources. “Our discovery of sodium chloride indicates that this population of asteroids could contain much more water than we previously believed.”

Most asteroids of this type burn up in Earth’s atmosphere and do not reach the surface. “You need a large enough rock to survive entry and deliver that water,” added Che.

Prior research suggested that water molecules in the early solar system could become trapped in asteroid minerals and survive impacts on Earth. “These studies imply that asteroids alone could deliver several oceans’ worth of water,” stated Tom Zega, the study’s senior author and a professor of planetary sciences at the Lunar and Planetary Laboratory. “If it turns out that the most common asteroids are much ‘wetter’ than anticipated, it would make the asteroid water delivery hypothesis even more plausible.”

It is suspected that the salt crystals in the sample have been present since the formation of the solar system 4.5 billion years ago.

Wishing you clear skies and wide eyes.