Reading aloud First yellow, then green was the fireball, which appeared in the middle of the night over the south of Morocco. Then the celestial phenomenon parted, and a witness heard twice a dull bang. Meanwhile, the astronomers know: What fell from the sky in the Moroccan desert on July 18, 2011, were fragments of the planet Mars. Information about the atmosphere, the soil and the interior of the Red Planet is contained in the meteorite, Hasnaa Chennaoui Aoudjehane and colleagues in the journal Science report. Nomads had collected the fragments with a total weight of seven kilograms. The meteorite was named Tissint, after the nearest town. Although there are more than 100 Martian meteorites in total, most have been on Earth for a long time before being discovered, and could therefore be polluted. The Tissint meteorite is only the fifth Mars meteorite that could be salvaged immediately after the crash. Most of the debris is covered by a dark enamel crust that has formed on entering the earth's atmosphere. When Chennaoui Aoudjehane and her colleagues examined some smaller fragments in more detail, they discovered that they are basalt rocks that have already weathered on Mars. Unusual on the rock are dark, glassy areas between large olivine crystals.
From their investigation, the researchers conclude that the basalt reached the surface of Mars millions of years ago by volcanic eruptions. Over time, the rock was attacked by an acidic liquid from the Martian soil, the researchers say. The sulfur and fluorine enriched liquid penetrated the cracks and crevices of the rock, forming new minerals there. At the impact that struck the rock out of the Martian soil, these minerals liquefied and then solidified in shock to dark glass.
The impact that threw the Tissint meteorite from Mars into space occurred about 700, 000 years ago. One knows a few other Mars meteorites with similar composition. This "Shergottite"? are probably fragments of the same cosmic collision.
Hasnaa Chennaoui Aoudjehane (University of Casablanca, Morocco) et al .: Science, Online Preliminary Issue, doi: 10.1126 / science.1224514 wissenschaft.de - Ute Kehse Anzeige