Tissint Martian Meteorite: A Fresh Look at the Interior, Surface, and Atmosphere of Mars

A New Rock from Mars On 18 July 2011 a meteorite originating from Mars fell on the moroccan desert. Chennaoui Aoudjehane et al. (p. 785, published online 11 October) show that this meteorite was ejected from the surface of Mars 700,000 years ago and contains components derived from the interior, surface, and atmosphere of the red planet. Previous to this fall, only four other martian meteorites have been collected after being witnessed falling to Earth. All the other martian meteorites that are represented in collections around the world, have been found long after their arrival on Earth, and thus have suffered from exposure to the terrestrial environment. A meteorite that fell in Morocco in July 2011 provides a sample to study processes that operated on Mars 700,000 years ago. Tissint (Morocco) is the fifth martian meteorite collected after it was witnessed falling to Earth. Our integrated mineralogical, petrological, and geochemical study shows that it is a depleted picritic shergottite similar to EETA79001A. Highly magnesian olivine and abundant glass containing martian atmosphere are present in Tissint. Refractory trace element, sulfur, and fluorine data for the matrix and glass veins in the meteorite indicate the presence of a martian surface component. Thus, the influence of in situ martian weathering can be unambiguously distinguished from terrestrial contamination in this meteorite. Martian weathering features in Tissint are compatible with the results of spacecraft observations of Mars. Tissint has a cosmic-ray exposure age of 0.7 ± 0.3 million years, consistent with those of many other shergottites, notably EETA79001, suggesting that they were ejected from Mars during the same event.