Interplanetary dust particles carry water generated with hydrogen solar wind.

Researchers from the University of Hawaiʻi at Mānoa’s School of Ocean and Earth Science and Technology, Lawrence Livermore National Laboratory, Lawrence Berkeley National Laboratory and University of California – Berkeley discovered that interplanetary dust particles could deliver water and organics to the Earth and other terrestrial planets.

Interplanetary dust, dust that has come from comets, asteroids and leftover debris from the birth of the solar system, continually rains down on the Earth and other Solar System bodies. These particles are bombarded by solar wind, which knocks the atoms out of order and leaves behind oxygen that is more available to react with hydrogen, for example, to create water molecules.

“It is a thrilling possibility that this influx of dust has acted as a continuous rainfall of little reaction vessels containing both the water and organics needed for the eventual origin of life on Earth and possibly Mars,” said Hope Ishii, an associate researcher in UH Mānoa’s Hawaiʻi Institute of Geophysics and Planetology and co-author of the study.

Implications of this work are potentially huge. Airless bodies in space such as asteroids and the Moon, with ubiquitous silicate minerals, are constantly being exposed to solar wind irradiation that can generate water. In fact, this mechanism of water formation would help explain remotely sensed data of the Moon, which discovered OH (hydroxide) and preliminary water, and possibly explains the source of water ice in permanently shadowed regions of the Moon.

“Perhaps more exciting,” said Ishii, “interplanetary dust, especially dust from primitive asteroids and comets, has long been known to carry organic carbon species that survive entering the Earth’s atmosphere, and we have now demonstrated that it also carries solar-wind-generated water. So we have shown for the first time that water and organics can be delivered together.”

It has been known since the Apollo-era, when astronauts brought back rocks and soil from the Moon, that solar wind causes the chemical makeup of the dust’s surface layer to change. Hence, the idea that solar wind irradiation might produce water-species has been around since then, but whether it actually does produce water has been debated.

Using a state-of-the-art transmission electron microscope, the scientists have now actually detected water produced by solar-wind irradiation in the space-weathered rims on silicate minerals in interplanetary dust particles.

In future work, the scientists will attempt to estimate water abundances delivered to Earth by interplanetary dust particles. Further, they will explore in more detail what other organic (carbon-based) and inorganic species are present in the water in the vesicles in interplanetary dust rims.

“Detection of solar wind-produced water in irradiated rims on silicate minerals” by UH Mānoa’s John Bradley, Ishii and Jeffrey Gillis-Davis and James Ciston, Michael Nielsen, Hans Bechtel and Michael Martin was published in the Proceedings of the National Academy of Science.

For more, read the A UH Mānoa news release.

—By Marcie Grabowski