Wednesday 18 January 2012

Fragments of Mars found in Morocco.

At about 2.00 am local time (the same as GMT) on 18 July 2011 a fireball was seen falling into the desert south of Tata in Morocco. In October local people started to find fusion-crusted black stones near the village of Tissint, and in December French meteor-hunter and dealer Luc Labenne visited the site and collected some samples, which he sent to the French National Museum of Natural History in Paris.

A piece of meteorite at Tissint. The outer layer has been blackened by its passage through the atmosphere. Photograph taken on 4 January 2012 by Abdelrahmane Ibhi.

In Paris the samples were examined by meteorite experts Brigitte Zanda and Violaine Sauter, who came to the conclusion that the meteors had fallen very recently, and were probably of Martian origin, an analysis that has now been supported by the Meteorological Society, an international society of scientists studying meteors, asteroids, comets and planetary bodies.

This has greatly increased the value of the meteors, which are reported to be changing hands for up to US$22 000 per ounce; Martian meteorites are highly sought after by both private collectors and academic institutions. There are thought to be about 106 kg of known Martian meteorites in collections on Earth, with about 7 kg of these coming from the Tissint Meteorite.

A Tissint Meteorite from the Macovich Collection. The cube is 1 cm² for scale. Photograph by Darryl Pitt.

Most meteorites are about 4.5 billion years old, dating from the origin of the solar system. Younger meteorites are assumed to have a planetary origin, having been blasted from the surface of planets by volcanic eruptions or the impact of other meteors. Studies of the surface and atmosphere of Mars have enabled scientists to diagnose some of these rocks as coming from Mars, even though we have never been able to bring back samples from the planet ourselves.

Most of the known Martian meteorites have ancient origins, having been found in deserts and on ice flows (meteorites are hard to locate in temperate climates, where their black colour blends in with dark soils), but Martian meteors have been recorded falling to Earth and collected before. The first fell in France in 1815, the next at Shergotty in India in 1865 (for which reason these meteorites are sometimes known as Shergotty Meteorites, since they have a distinctive chemical signature, but could not be connected with Mars until quite recently), then in 1911 in Egypt and 1962 in Zagami in Nigeria, where the meteorite reputedly missed a local farmer by about 3 meters. This suggests that some ancient event on Mars threw a cloud of debris into space, through which the Earth passes every 50 years.