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Interplanetary dust jump-started life on Earth?

Last Updated: Sunday, January 26, 2014 - 19:40

Washington: Dust coming from comets and asteroids may have delivered water and organics to the Earth - jump starting life on our planet, US researchers say.

Interplanetary dust, dust that has come from comets, asteroids, and leftover debris from the birth of the solar system, continually rains down on Earth and other Solar System bodies, researchers said.

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.

"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, from the University of Hawaii - Manoa (UHM) and co-author of the study.
This mechanism of delivering both water and organics simultaneously would also work for exoplanets, worlds that orbit other stars, researchers said.

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 and preliminary water, and possibly explains the source of water ice in permanently shadowed regions of the Moon.

"Perhaps more exciting 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," said Ishii.

It is known that solar wind causes the chemical makeup of the dust`s surface layer to change, researchers said.

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 are that the amount of water produced is small and it is localised in very thin rims on the surfaces of silicate minerals so that older analytical techniques were unable to confirm the presence of water.

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.

On the bases 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.

PTI
First Published: Sunday, January 26, 2014 - 19:40
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