Space Dust Carries Water and Organic Carbon

Could Space Dust have Delivered Life’s Ingredients to Earth?

Water forms on interplanetary dust particles due to space-weathering from the solar wind. Hydrogen ions in the solar wind react with oxygen atoms in the dust to form tiny water-filled vesicles(blue). Credit: John Bradley, UH SOEST/ LLNL

For the first time, scientists have detected water molecules on the surface of interplanetary dust particles. The water forms in tiny bubbles when solar wind irradiates and damages the dust grains floating through space.

Previous research had shown that space dust also contains organic carbon–another key ingredient for life. Taken together, these findings raise the intriguing possibility that dust trickling down from space could have seeded life’s building blocks on our own planet–and potentially elsewhere.

Dust in the Solar Wind

For the past 40 years, researchers have debated whether solar wind could actually produce water. When astronauts brought rocks and soil back from the Moon, scientists had noticed that solar wind irradiation creates pockets of damage on the outer layers of space objects that lack a protective atmosphere.

They quickly realized that water could potentially be created by this process. Dust grains come from the breakdown of comets, asteroids, and leftover debris from the birth of the solar system. They contain a lot of silicate, a mineral made of silicon and oxygen.

Solar wind mainly blasts clouds of hydrogen ions into space. When the wind hits cosmic debris, the ensuing damage loosens the oxygen atoms, which are then free to react with the solar wind’s hydrogen, potentially resulting in the formation of tiny pockets of water.

But the amount of water was too small to be detected–until now.

The research team, led by John Bradley of the University of Hawaii in Honolulu, used a state-of-the-art transition electron microscope to finally detect these water pockets on cosmic dust. The samples had previously been collected by high-flying NASA aircrafts, and curated by the Astromaterial research group at the NASA Johnson Space Center.

The team confirmed their finding by simulating the process in the laboratory. The work was conducted at the Lawrence Livermore National Laboratory in California, and the findings were published this month is the journal Proceedings of the National Academy of Sciences.

Seeds of Life?

The findings open a new intriguing possibility about the origins of life on Earth. Some theories had suggested that life was seeded on Earth by comets or asteroids bombarding the early Earth’s surface, before the planet got its protective atmosphere.

“Our work shows that it could have been a much more gentle process, with this fine dust trickling down gently, carrying both organic carbon and water,” says Hope Ishii, a co-author of the study now at the University of Hawaii in Honolulu.

Artist impression of an exoplanet. Credit: ESO

“In the process of entering the earth’s atmosphere, the dust grains are heated. So the dust particles may act like little incubators for chemical reactions, like localized vessels carrying organic compounds and water together.”

But the findings do not suggest that Earth’s oceans were formed by this process.

Today, our Earth accumulates 30,000 to 40,000 tons of space dust every year. But that amount is hard to estimate overtime. “The amount of dust falling from space was much larger in the early Earth history, “Ishii explains. “And our sun was also much brighter in the past.”

“We don’t know how much water is produced by this method. There’s just too many factors we’d have to estimate,” she says.

Universal Delivery

Could space dust have delivered life’s ingredients to planets outside our solar system as well?

“Anywhere there’s dust, and anywhere a star generates solar wind, we should expect this water-forming process to happen,” Ishii says. “It’s such a tantalizing possibility–that this process may have contributed to the origins of life not only on Earth, but possibly elsewhere.”

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