How the moon got its whiskers
15:05 02 July 2010 by Kate McAlpine
For similar stories, visit the Solar System Topic Guide
Famous for its crater-pocked face, it now turns out that the moon has whiskers too. How did the moon get such adornments?
Slender wisps of carbon graphite, rolled up into sheets just a single atom thick, have been found in a sample of lunar rock. The best bet is that they arrived in a meteor shower that may also have dumped molecules essential for life.
Graphite just one atom thick is better known as graphene, and prized for its strength and exotic electrical properties. It is typically made in labs by depositing a thin layer of carbon onto a surface.
When Andrew Steele of the Carnegie Institution for Science, Washington DC, and colleagues shone a green laser at a sample of moon rock, known as regolith, collected by the Apollo 17 mission 40 years ago, the light signal that was returned revealed a crystal structure consistent with whiskers of graphene.
The rock is about 3.9 billion years old, from the time when heavy meteor bombardment gave the moon its crater-pocked surface.
This bombardment is also thought to have given Earth volatile elements and compounds crucial to life – such as hydrogen, nitrogen, carbon dioxide, and water. These compounds would have previously boiled off in the magma ocean that made up the surface of the young, hot earth at around the same time that the Moon formed, says Steele.
John Bridges of the University of Leicester, UK, says the discovery of carbon whiskers on the moon provides further evidence for the theory that the meteor shower helped seed life on Earth. “It’s a nice first identification of graphite in the lunar regolith,” he adds.
The whiskers may have arrived, ready-made on the meteoroids, or else condensed into curled sheets from the hot, carbon-rich gas produced in the impact.
Mahesh Anand of the Open University, London, is not surprised that lunar rock contains graphite, but he is impressed that Steele’s group managed to find something new in an old sample “commonly believed to have been subjected to exhaustive studies”.