Tissint

In 2011 a fireball over the Moroccan desert delivered the freshest pieces of Mars that scientists had seen in half a century.

Key facts

Type

Martian meteorite (olivine-phyric shergottite)

Fell or found

Fell (witnessed)

Year

2011 (18 July)

Country

Morocco

Mass

about 7 kg recovered

Official name

Tissint

In the early hours of 18 July 2011, people in the Tata region of southern Morocco, near the village of Tissint, saw a bright fireball in the night sky. Some heard sonic booms as it broke up. For a few months nothing happened. Then, in October, local people began finding stones with a shiny black crust in a remote desert area. Word spread, and searchers combed the region. Altogether about 7 kilograms were recovered. When scientists examined them, they made an exciting discovery: the stones came from Mars.

A rare event

Tissint was only the fifth Martian meteorite ever seen to fall, after Chassigny in France in 1815, Shergotty in India in 1865, Nakhla in Egypt in 1911 and Zagami in Nigeria in 1962. Hundreds of Martian meteorites have been found, mostly in hot deserts and Antarctica, but almost all of them lay on Earth's surface for thousands of years before anyone picked them up. Over that time they are altered by weathering and contaminated by terrestrial salts, minerals and even microbes. Tissint was collected only months after it landed, in a dry desert, making it exceptionally fresh.

What the stones look like

Fresh Tissint stones are covered in a glossy black fusion crust, the glassy skin formed as the meteorite's outer surface melted during its blazing passage through the air. Inside, the rock is pale to dark grey, studded with large yellowish-green crystals of olivine. It is an olivine-phyric shergottite, meaning a shergottite in which big olivine crystals are set in a finer-grained background. It formed from molten rock that came from deep within Mars and cooled as it rose towards the surface, a few hundred million years ago, like other shergottites. The contrast between the glossy black skin and the pale interior makes Tissint stones easy to recognise.

Tissint is also full of shock-melted glass, dark pockets and veins formed when the rock was hit by the impact that blasted it off Mars. These glassy areas trapped samples of gases from Mars's thin atmosphere. Their make-up matches measurements made by spacecraft that landed on Mars, confirming the meteorite's origin.

Clues about Martian chemistry

Scientists have used Tissint to study the Martian interior and surface. Because it was so fresh, researchers could look for substances that might otherwise be dismissed as contamination from Earth. One team reported carbon-rich material in tiny cracks inside the meteorite that they argued was of Martian origin, perhaps deposited by fluids moving through rocks near the Martian surface. Other researchers have identified high-pressure minerals in its shock veins, created in the split second of the launching impact. The meteorite has also helped scientists to compare Martian samples with data from rovers and orbiters.

A meteorite rush

The discovery set off a scramble among local searchers, dealers and collectors, as Martian meteorites are among the most sought-after of all. Pieces reached museums, universities and private collections around the world. Moroccan scientists played an important part in documenting the fall and studying the stones, and samples are held in Morocco as well as abroad. The Natural History Museum in London acquired a significant specimen, as did other major collections.

Why it matters

Tissint is one of the best samples of Mars available on Earth. It gives scientists a fresh, uncontaminated piece of the Martian interior and a snapshot of its atmosphere, delivered for free by nature. Until spacecraft bring back samples collected on Mars itself, meteorites like Tissint remain our only physical pieces of the Red Planet. Its story also shows how important it is that fireball sightings are reported, and that finds are shared with scientists so that they can be properly recorded and studied.

Did you know?

See more

Tissint in the catalogue