Interplanetary dust started life on earth?
Dust from comets, asteroids and leftover debris may have delivered water needed for the eventual origin of life on earth and possibly Mars.
In a thrilling discovery, researchers have found that interplanetary dust - long been known to carry organic carbon species that survive entering the earth's atmosphere - may have delivered water and organics together.
"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 origin of life," said Hope Ishii, associate researcher at the University of Hawaii at Manoa.
Using a state-of-the-art transmission electron microscope, the scientists have detected water produced by solar-wind irradiation in the space-weathered rims on silicate minerals in interplanetary dust particles.
On the basis of laboratory-irradiated minerals that have similar amorphous rims, they were able to conclude that the water forms from the interaction of solar wind hydrogen ions (H+) with oxygen in the silicate mineral grains.
In no way the study suggests that the rainfall from dust particles was sufficient to form oceans.
"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," Ishii said.
"We would now explore in more detail what other organic (carbon-based) and inorganic species are present in the water in the vesicles in interplanetary dust rims," she added.
Ishii's team included researchers from the Lawrence Livermore National Laboratory, the Lawrence Berkeley National Laboratory and the University of California - Berkeley.
Interplanetary dust continually rains down on earth and other solar system bodies. These particles are bombarded by solar wind, predominately hydrogen ions.
This ion bombardment knocks the atoms out of order in the silicate mineral crystal and leaves behind oxygen that is more available to react with hydrogen, for example, to create water molecules.
This mechanism of delivering both water and organics simultaneously would also work for exoplanets - worlds that orbit other stars.
This mechanism of water formation would help explain the source of water ice in permanently shadowed regions of the moon.
(Posted on 26-01-2014)