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Secret to loony lunar soils revealed

Lunar secrets Glass bubbles in lunar soil are the source of nanoparticles that explain the alien behaviour of the Moon's topsoil, say researchers.

Dr Marek Zbik from the Queensland University of Technology and colleagues report their findings in the International Scholarly Research Network Astronomy and Astrophysics.

Lunar soil particles are very sticky and abrasive, says Zbik, a surface chemist and geologist, whose work was sponsored by the Australian Synchrotron.

The particles are also electrically charged which means they hover above the surface of the Moon.

"Usually it's just a few centimetres up, but they can also be present 100 kilometres up," says Zbik.

Not only can these particles coat surfaces of equipment, windows and electrical components, they can also present a potential human health hazard.

In addition, lunar soil particles are very good insulators, says Zbik. Even though it can be 160°C above the Moon's surface, 2 metres below the surface it can be just -40°C.

Scientists believe these weird properties of the Moon's soil can be explained by the numerous nanoparticles contained within it.

"Nanoparticles are ruled by quantum physics, which is poorly understood," says Zbik.

But to date it has been a mystery about where these tiny particles - just 100 nanometres in size - came from.

"If you grind rock you cannot obtain particles less than 2 microns in diameter," says Zbik.

Glass bubbles

In earlier studies Zbik had used scanning electron microscopy to study samples of lunar soil from a Soviet robotic space mission.

In particular he studied fragments of glass formed from the melting of lunar soil after meteorite impacts, and found evidence of broken bubbles containing nanoparticles.

"I was surprised when I saw the nanoparticles in the bubbles and wondered where they had originally from," says Zbik.

In the most recent study, Zbik and colleagues used transmission x-ray microscopy to study intact bubbles in the glass, and found they contained a sponge-like network of nanoparticles.

Zbik says the study confirms the bubbles are indeed the source of the nanoparticles, which would have been released by subsequent meteorite bombardment which broke open the bubbles.

"The nanoparticles were then liberated and incorporated into the lunar soil," says Zbik.

Zbik says the next step is to understand how the nanoparticles were formed inside the bubbles in the hope of finding commercially-relevant techniques for making nanoparticles.