Murchison meteorite

The Murchison meteorite is named after the place it fell: Murchison, Victoria, Australia.  It is large (over 100 kg) and it was seen falling.  It is one of the most studied meteorites, since it belongs to a group of meteorites rich in organic compounds, known as carbonaceous chondrites.

On 28 September 1969 at about 10:58 am, a bright fireball was seen. It separated into three fragments before disappearing, leaving a cloud of smoke. About 30 seconds later, a tremor was heard. People found fragments over an area larger than 13 km², with fragments up to 7 kg. One, weighing 680 g, broke through a roof and fell in hay.The Meteorite Society database The mass is over 100 kg.

 The biochemistry 
This type of meteorite is rich in carbon.Planetary science research discoveries: glossary Murchison contains over 15 amino acids.Nonprotein amino acids from spark discharges and their comparison with the Murchison Meteorite amino acids. Kvenvolden K. et al 1972. Proc. Nat. Acad. Sci. USA 69, 4, 809-811. The amino acids found in the Murchison meteorite can be (and have been) synthesised in laboratory experiments. This was done by the action of electric discharge on a mixture of methane, nitrogen, and water with traces of ammonia.

The amino acids were mostly racemic. This means the chirality of their enantiomers are almost  equally left- and right-handed. This suggests they are not caused by terrestrial contamination. A complex mixture of alkanes was isolated as well, similar to that found in the Miller-Urey experiment. Serine and threonine, often earthly contaminants, were absent from the samples.

In 1997 research showed that individual amino-acids from Murchison were enriched in the nitrogen isotope 15N relative to their terrestrial counterparts. This confirmed an extraterrestrial source. The organic materials identified included sugar-like compounds (polyols).

 Compound class Concentration (ppm)Amino acids   17-60Aliphatic hydrocarbons  >35Aromatic hydrocarbons  3319Fullerenes  >100Carboxylic acids  >300Hydrocarboxylic acids  15Purines and pyrimidines   1.3 Alcohols  11 Sulphonic acids 68Phosphonic acids  2

Several lines of evidence show that the inside of well-preserved fragments from Murchison are pristine (not contaminated). A 2010 study identified  14,000 molecular compounds (including 70 amino acids) in a sample of the meteorite. There may be 50,000 or more different molecular compositions in the meteorite.

 Nucleobases 
Measured purine and pyrimidine compounds are in the Murchison meteorite. Carbon isotope ratios for uracil and xanthine show a non-terrestrial origin for these compounds. The results show many organic compounds which are components of life on Earth were already present in the early Solar System. They may have played a  role in life's origin.

 References 

Category:Meteorites
Category:Impact events