Picture 1. Image of small fragment of Tissint meteorite.
A fresh meteorite, which was witnessed falling in Morocco last year, has been found to contain traces of material from both the surface and atmosphere of Mars, according to a new paper published today in Science.
The meteorite fell to Earth in a fireball on 18th of July 2011 near Tissint, a Moroccan town along the Algerian border. As it is only the fifth witnessed fall of a Martian meteorite to have been recovered, the rock has provided a unique opportunity for researchers to expand their understanding of Mars. Previous Martian meteorites have suffered varying degrees of terrestrial contamination. In contrast, the Tissint meteorite is so fresh that it has been possible to detect evidence of components from both the Martian surface and atmosphere. The features observed in Tissint are broadly compatible with previous observations made by spacecraft sent to Mars by NASA and ESA.
The meteorite is a type of Martian volcanic rock known as a shergottite and contains abundant glass produced by impact processes on Mars. When this glass formed it trapped not only a sample of the Martian atmosphere, but also traces of soil-like material. The composition of the trapped atmosphere is very close in composition to that detected by the NASA Viking landers in the 1970s and so unambiguously demonstrates that the meteorite is from Mars. The glass also displays relatively high levels of sulphur and fluorine which, together with its distinct trace element signature, indicates that it contains material from the Martian surface.
A further important finding of the study is that Tissint has a similar cosmic ray exposure age to a number of other Martian meteorites, including the important sample EETA79001, collected in Antarctica. It would seem that all these meteorites were ejected into space by a single impact event that took place on Mars around 700,000 years ago.
The research results presented in Science were conducted by an international team of twenty scientists, including four researchers from the Open University. The Open University team undertook detailed carbon, nitrogen and oxygen isotope measurements on Tissint that not only authenticated its Martian origin, but were able to decipher the various atmospheric and soil components it contains.
Professor Monica Grady, head of the Open University’s Physical Sciences Department and one of the scientists who worked on Tissint says: “Tissint is an extremely important sample that has provided us with very fresh material from the surface of Mars that we can study in the laboratory. The recognition of Martian weathering products in Tissint will provide important constraints for the interpretation and evaluation of data currently being collected on Mars by the NASA Curiosity rover.”
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