January 27, 2014
Interstellar Dust Particles Carry Water, Organic Compounds To Earth
[ Watch the Video: What Could Be Raining Down Life In Our Solar System? ]
redOrbit Staff & Wire Reports - Your Universe OnlineDust that originates from comets, asteroids and leftover debris from the birth of the Solar System could deliver water and organic material to the Earth and other terrestrial planets, according to a recent Proceedings of the National Academy of Science paper.
In the study, researchers from the University of Hawaii-Manoa (UHM) School of Ocean and Earth Science and Technology (SOEST), the Lawrence Livermore National Laboratory (LLNL), the Lawrence Berkeley National Laboratory and the University of California-Berkeley explain that these interplanetary dust particles (IDPs) continually rain down upon our planet and other worlds in our Solar System.
The IDPs are bombarded by solar wind, especially hydrogen ions, and these ions disturb the order of the atoms in the silicate mineral crystal. This process leaves behind oxygen, which is more readily available to react with hydrogen in order to create water molecules, the study authors explained in a statement Friday.
“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 study co-author and UHM SOEST Hawaii Institute of Geophysics and Planetology (HIGP) associate researcher Hope Ishii.
“This mechanism of delivering both water and organics simultaneously would also work for exoplanets, worlds that orbit other stars. These raw ingredients of dust and hydrogen ions from their parent star would allow the process to happen in almost any planetary system,” the university added. “Implications of this work are potentially huge.”
For example, airless bodies such as the Moon and asteroids, with abundant amounts of silicate minerals, are being exposed to solar wind irradiation constantly. This mechanism could generate water, and would help explain remotely sensed Moon data that detected OH and preliminary water, the researchers said. Furthermore, it might help explain what caused water ice to form in the permanently shadowed areas of the lunar surface.
“Perhaps more exciting,” Ishii said, "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,” the university added. “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.”
The reasons for the uncertainty is that only small quantities of water are produced, and only in specific areas (thin surface rims of silicate minerals). As such, older analytical techniques were unable to confirm the presence of water, but scientists have actually managed to use a state-of-the-art transmission electron microscope to detect water produced by solar-wind irradiation in the space-weathered rims on silicate minerals in IDPs.
Furthermore, on laboratory-irradiated mineral bases with similar amorphous rims, Ishii and her colleagues were able to determine that water forms from the interaction between solar wind hydrogen ions (H+) and oxygen in the silicate mineral grains. However, they do not know how much water may have been delivered to Earth using this method.
“In no way do we suggest that it was sufficient to form oceans, for example,” Ishii said. “However, the relevance of our work is not the origin of the Earth's oceans but that we have shown continuous, co-delivery of water and organics intimately intermixed.”
“In future work, the scientists will attempt to estimate water abundances delivered to Earth by IDPs,” the university added. “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.”