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A special kind of opal that can trap microbes on Earth has been found in a Martian meteorite, suggesting a new target in the search for signs of life on Mars.
The meteorite Nakhla, held in the collections of the Natural History Museum, has been found to contain microscopic traces of a mineral known as fire opal by a team from the University of Glasgow.
On Earth, fire opals form around hydrothermal vents on the sea floor – hot, chemically-rich areas where microbes thrive. As the opals form, through the interaction of rocks with the seawater, they can trap microbes.
Analyses of the surface of Mars appear to show areas of opal, but the discovery of fire opals in the Nakhla meteorite is the first direct proof that they can form on the planet. The opal regions of Mars could now be a good target for future explorations looking for signs of early life.
Lead author Prof Martin Lee, from the University of Glasgow, said: ‘The slice of Nakhla that we have is small, and the amount of fire opal we’ve found in it is even smaller, but our discovery of opal is significant. If Martian microbes existed, it’s possible they may be preserved in opal deposits on the surface of Mars.’
The findings were reported this week in the journal Meteoritics and Planetary Science. The opals were investigated with a powerful scanning electron microscope and found to be most similar in structure to fire opals on Earth, so named for their brilliant orange, yellow and red colouration.
The volcanic rocks that make up the meteorite are 1.3 billion years old, but previous studies on the Nakhla meteorite by the same group have shown that water altered the rocks around 630 million years ago. The meteorite fell to Earth in 1911 near the village of El Nakhla El Bahariya in Egypt.
Dr Caroline Smith, Museum Curator of Meteorites and co-author of the study, said: ‘We are able to use specimens from the Museum's meteorite collection and study them using sophisticated laboratory techniques to confirm findings from Mars’ robotic exploration missions.
‘This combination of data, from rovers, orbital missions and earth-based analyses of Martian meteorites, is providing yet more evidence of Mars' geological history and the tantalising possibility that it had environmental conditions perhaps capable of supporting life.’