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Credit: Birger Rasmussen
By Charles Q Choi
A mineral once found only on the moon has now been discovered in billion-year-old rocks in Australia. Tranquillityite is a mineral consisting of iron, zirconium, yttrium, titanium, silicon and oxygen. It is named after the moon's Sea of Tranquility, where it was first discovered on the Apollo 11 mission. Until now, it was only seen in samples returned from the moon, as well as in lunar meteorites — that is, rocks blasted off the moon's surface by cosmic impacts that crash-landed here.
Now scientists have identified what appear to be terrestrial versions of tranquillityite in Western Australia. The mineral commonly occurs as clusters of thin, narrow, fox-red strips in dikes or sills — bodies of rock that likely originally intruded as magma into surrounding layers of stone. Its composition is largely the same as lunar tranquillityite.
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