Using light to describe the ancient world

Possible Martian fossil… but not if Raman spectroscopy has anything to say about it . Image from Nasa (details below).

The search for extra terrestrial life is not all peering through telescopes looking for someone peering back – it also involves looking for alien fossils. It was during this noble quest that astrobiologists (=space paleontologists) became incredibly excited when they studied the surface of a Martian meteorite found in Allan Hills, Antarctica (meteorite ALH84001). David McKay and colleagues (1996) reported possible organic structures in ALH84001, a gift from our celestial neighbour. Debate ensued, and Raman spectroscopy was eventually called in to help clarify whether ALH84001 showed signs of life. Steele and colleagues (2007) analysed regions of the meteorite that contained carbonate, an anion mineralised in both sea shells and volcanoes. The variation in carbonate chemistry within ALH84001, as indicated by Raman Spectroscopy, was consistent with carbonate minerals in one million year old volcanic rocks from Svalbard. This meant that the Martian meteorite structures could have been made by simple rock-melting, and didn’t have to have an alien fossil explanation. Way to ruin a party, Raman spectroscopy.

McKay DS, Gibson Jr EK, Thomas-Keprta KL, Vali H, Romanek CS, Clemett SJ, Chillier XDF, Maechling CR, Zare RN (1996) Search for past life on Mars: possible relic biogenic activity in Martian meteorite ALH84001. Science 273:924-930.

Steele A, Fries MD, Amundsen HEF, Mysen BO, Fogel ML, Schweizer M, Boctor NZ (2007) Comprehensive imaging and Raman spectroscopy of carbonate globules from Martian meteorite ALH 84001 and a terrestrial analogue from Svalbard. Meteoritics and Planetary Science 42:1549-1566.

Image: ALH84001


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