Tatahouine
A meteorite that shattered into green crystals in the Tunisian desert in 1931 – a fragment from deep inside the asteroid Vesta.
Key facts
- Type
- Achondrite (diogenite, HED group)
- Fell or found
- Fell (witnessed)
- Year
- 1931 (27 June)
- Country
- Tunisia
- Mass
- about 12 kg, in many fragments
- Official name
- Tatahouine
On the morning of 27 June 1931, people near the town of Foum Tatahouine in southern Tunisia heard a loud explosion and saw a meteoroid break apart in the sky. A shower of fragments fell onto the rocky desert. Unlike most meteorites, which fall as solid stones with a dark crust, many of these pieces shattered as they hit the ground. Altogether about 12 kilograms were gathered, most as small, angular fragments. When people looked closely at them, they saw something unusual: the pieces were made of glassy, bottle-green crystals.
A rock made of one mineral
Tatahouine is a diogenite, a type of achondrite. Achondrites are stony meteorites that formed from melted rock and so lack chondrules, the small round grains found in most stony meteorites. Diogenites are made almost entirely of a single mineral: orthopyroxene, a magnesium-iron silicate. In Tatahouine, the orthopyroxene crystals are large and green, and the rock is so coarsely crystalline and fractured that it broke easily into fragments when it struck the ground.
The name 'diogenite' honours Diogenes of Apollonia, an ancient Greek thinker who is said to have suggested that meteorites come from beyond the Earth. The French mineralogist Alfred Lacroix, a leading meteorite scientist of his day, described the Tatahouine fall soon after it happened.
From deep inside Vesta
Diogenites belong to the HED family of meteorites, together with howardites and eucrites. All three are thought to come from the asteroid Vesta, one of the largest bodies in the asteroid belt. Vesta melted early in Solar System history and separated into layers, much like a small planet, with a metal core, a rocky mantle and a basaltic crust.
Eucrites are lava-like rocks from the crust. Diogenites formed deeper down, where crystals of orthopyroxene grew slowly in cooling bodies of magma and accumulated. Howardites are mixtures of the two, churned together on the surface by impacts. Tatahouine is therefore a sample from the lower crust or upper mantle of Vesta, brought to the surface by a huge impact. NASA's Dawn spacecraft, which orbited Vesta in 2011 and 2012, found diogenite-like rock exposed in the walls and floor of the giant Rheasilvia impact basin near the asteroid's south pole, exactly where such deep material might be expected to show.
A natural experiment in weathering
Tatahouine has a second claim to fame. In the 1990s, about 60 years after the fall, scientists returned to the site and collected fragments that had lain buried in the desert soil since 1931. Comparing them with pieces collected immediately after the fall showed how quickly Earth's environment begins to alter a meteorite. Within a few decades, the buried fragments had acquired coatings of desert minerals and showed signs of colonisation by microorganisms from the soil. The study was an important warning for researchers looking for signs of life in meteorites: contamination from Earth can creep in surprisingly fast.
A famous name
The town of Tataouine, as its name is often spelled, is also known for another reason. Its name inspired that of the desert planet Tatooine in the Star Wars films, parts of which were filmed in southern Tunisia. The meteorite, however, is very much real.
Why it matters
Tatahouine is one of the classic diogenite falls and among the most striking meteorites to look at, with its glassy green crystals. It provides fresh material from deep inside Vesta, helping scientists understand how the asteroid's interior formed and cooled. Its long-term weathering study also made it an important reference for recognising contamination in meteorites found in deserts.
If you ever see a piece of Tatahouine, hold it up to the light. Those green crystals grew slowly in a magma chamber inside an asteroid more than 500 kilometres across, about 4.5 billion years ago, and then travelled across the Solar System to land in the Tunisian desert.
Did you know?
Tatahouine shattered into many small green fragments when it hit the ground.
Fragments collected about 60 years after the fall showed how quickly Earth's environment alters meteorites.
The town's name inspired that of the desert planet Tatooine in the Star Wars films.