Water in interplanetary dust

U.S. researchers have discovered a new source of water in our solar system and, conceivably, in each star system. The water is generated in interplanetary dust particles under the influence of the solar wind.


A U.S. research group, led by John Bradley of the Lawrence Livermore National Laboratory in California, has succeeded for the first time in reliably detecting the presence of water within interplanetary dust grains. The result, published in the Proceedings of the National Academy of Sciences, has been possible thanks to the VEELS (valence electron energy -loss spectroscopy), a technique of high- resolution microscopy. Bradley and colleagues examined the outer layer of particles collected in the Earth’s stratosphere, tiny bits of interplanetary dust with sizes between 5 and 25 micrometers. Just below the surface, a very thin layer (rim) in which they occurred chemical reactions induced by cosmic weather, the researchers identified the water trapped in tiny “pockets”.

It may seem strange, but the source of that water is due to the solar wind, which is a phenomenon of helium lysis caused by charged particles from the Sun at high speed. The chemical structure of the surface of dust grains is changed, along with other agents from the constant bombardment of the solar wind, causing an imbalance that weakens the bonds between the atoms of hydrogen and oxygen in silicates. With the contribution of additional hydrogen atoms, present in abundance in the solar wind in the form of high-energy ions, they can form water molecules.

A process already known and reproduced in the laboratory, but had not yet had a clear experimental confirmation of true particles of space dust, mainly because of the small size at which this reaction takes place and the consequent difficulty instrumental in distinguishing unambiguously the presence of  water. “The implications are potentially enormous,” said Hope Ishii, a researcher at the University of Hawaii in Honolulu involved in the study. “It is particularly exciting to think of the possibility that the influx of these powders on the surface of bodies of the solar system may have acted as a continuous rain of micro- chemical laboratories, containing both water and organic compounds that may be necessary to give rise to life.”

Although it seems quite likely that the interplanetary dust may have actually brought water to Earth as falling rain in ancient times, it also seems unlikely that it can be the source of millions of cubic kilometers of water covering our planet today. “In no way are we suggesting that this was sufficient to form the oceans,” it takes to clarify Ishii.

If the contribution of “wet” asteroids and/or comets is that the hypothesis becomes more plausible to explain the large volume of water on Earth, the results of the team of Bradley are relevant to the search for life on other planets. In the state of current knowledge, the researchers say, that is in fact why the reaction that produces water in the dust grains cannot occur anywhere else in the universe where there is a star, or maybe even a supernova. In addition, if this “stardust” contains both water and carbon compounds, it means that the basic building blocks for life may be present in all stellar systems, drizzling on their planets.

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