illustration of comet 238P/Read

Salt crystals confirm that Earth’s water arrived on asteroids

Tiny crystals of salt in a sample collected from the Itokawa asteroid by the Hayabusa mission in 2005, and which reached Earth in 2010, could only form in the presence of liquid water.


We know that water on Earth is older than our sun. But where did that water come from? And how did it end up on Earth? The recent detection of minuscule salt crystals in an asteroid sample retrieved by Japan’s Hayabusa spacecraft suggests a broader presence of liquid water within the solar system’s predominant asteroid class than formerly surmised. According to experts, this hints that Earth’s water did indeed arrive on asteroids.

Ordinary Table Salt, Extraordinary Discovery

Contrary to expectations, table salt or sodium chloride has piqued the interest of researchers at the University of Arizona Lunar and Planetary Laboratory. Their excitement is derived from the discovery of these salt crystals within an asteroid sample. The presence of these crystals indicates they formed under liquid water conditions.

In an intriguing turn of events, the researchers reveal the sample originated from an S-type asteroid, known for its dearth of water-bearing minerals. This discovery, published in Nature Astronomy, lends credibility to the theory that asteroids could have brought Earth’s water during its volatile infancy.

Uncovering the Asteroid’s Salty Secret

The senior author of the study, Tom Zega, and lead study author Shaofan Che undertook a meticulous analysis of samples collected in 2005 from asteroid Itokawa by the Hayabusa mission. Their research establishes the salt crystals’ genesis on the asteroid itself, ruling out contamination on reaching Earth – a recurring issue in past studies.


The study presents an unusual possibility: that asteroids consisting of ordinary chondrites, a rock type common on Earth, could harbor more water than previously believed. Zega and Che’s discovery of sodium chloride brings a new perspective on this asteroid type as a potential water source.

Rethinking Theories about Earth’s Water Origins

This revelation may compel scientists to reevaluate how water was delivered to the early Earth. The prevailing theory attributes Earth’s water delivery to comets or C-type asteroids from the colder, outer reaches of the solar nebula.

The team painstakingly eliminated the possibility of sodium chloride contamination from various sources, including human sweat, lab moisture, or sample preparation procedures. A control experiment confirmed that the salt was native to Itokawa, assuring the team of the sample’s purity.

Asteroids – The Rain of Life?

Zega points out that, while tons of extraterrestrial matter daily reach Earth’s atmosphere, most burn up before reaching the surface. Only a sizable rock could deliver its watery cargo, potentially explaining our planet’s water origins.

Itokawa, a small near-Earth asteroid, is thought to have broken off from a larger parent body. Zega and Che suggest it could have hosted frozen water and sodium chloride, with heat from radioactive decay and meteorite bombardment fostering hydrothermal processes involving liquid water.


Salt Crystals – A Relic of the Early Solar System?

Finally, the presence of a sodium-rich vein in the sample, associated with water-induced alteration, reinforces the idea of water activity on the asteroid. The findings offer fresh insights into our understanding of the solar system’s watery past.

Have something to add? Visit Curiosmos on Facebook. Join the discussion in our mobile Telegram group.

Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

Write for us

We’re always looking for new guest authors and we welcome individual bloggers to contribute high-quality guest posts.

Get In Touch