Dar al Gani 476
A Martian rock found in the Libyan Sahara in 1998, packed with olivine crystals and part of a family of desert finds.
Key facts
- Type
- Martian meteorite (olivine-phyric shergottite)
- Fell or found
- Found
- Year
- 1998
- Country
- Libya
- Mass
- about 2 kg
- Official name
- Dar al Gani 476
In 1998, meteorite searchers working in the Dar al Gani region of the Libyan Sahara found a dark, greenish-brown stone weighing about 2 kilograms. Like other meteorites from that area, it was named after the place where it was found and given a number: Dar al Gani 476, often shortened to DaG 476. When scientists studied it, they discovered that it was a piece of Mars. Later, several more pieces of the same meteorite were found nearby and given their own numbers. Martian meteorites are named in exactly the same way as any other meteorite, so nothing in a name like DaG 476 tells you that it came from Mars: only laboratory study can.
Why the Sahara?
Hot deserts like the Sahara are excellent places to find meteorites. The dry climate slows down weathering, and dark meteorites are easy to spot on pale, stony desert surfaces. Some parts of the Sahara, including Dar al Gani, are flat plains of light-coloured limestone where meteorites stand out especially clearly. Since the 1990s, searches in such regions have found thousands of meteorites, including many rare types, such as meteorites from Mars and the Moon.
What it is
DaG 476 is an olivine-phyric shergottite. Shergottites are the most common group of Martian meteorites, named after the Shergotty meteorite that fell in India in 1865. 'Olivine-phyric' means that DaG 476 contains large crystals of the mineral olivine set in a finer-grained groundmass of pyroxene and shock-transformed feldspar glass. This texture shows that the olivine crystals grew first, in a magma deep below the surface, and then the rest of the magma cooled and crystallised more quickly, probably closer to the surface.
Like other shergottites, DaG 476 was shocked by the impact that blasted it off Mars. It contains shock-melted glass and minerals that were changed by high pressure.
Paired stones
After DaG 476 was identified as Martian, searchers found several more stones in the same area with the same unusual composition. These were given separate numbers, such as DaG 489, DaG 670, DaG 735 and DaG 876, but they are considered paired, meaning they came from the same fall. Together they provide a larger amount of material for research.
Desert weathering
Because DaG 476 lay in the desert for a long time before it was found, it has been affected by Earth's environment. Weathering has introduced carbonate minerals from the desert into cracks within the rock, and some of its original features have been altered. Scientists must carefully distinguish between features that formed on Mars and those that formed on Earth. This has made DaG 476 a useful case study in how desert meteorites become contaminated, which is important when searching for evidence of Martian water or organic material.
Why it matters
DaG 476 was one of the first Martian meteorites found in a hot desert, and its discovery showed how productive the Sahara could be for finding rare meteorites. Its olivine-rich composition helps scientists understand the variety of magmas on Mars, how they formed in the planet's mantle, and how they evolved as they rose to the surface.
It also illustrates both the opportunities and challenges of desert finds. Hot deserts have greatly increased the number of known Martian meteorites, but desert weathering and the lack of precise records for some finds can complicate research. Careful documentation, including the exact location of a find, makes meteorites far more valuable to science.
Libya, like many countries, has laws governing the collection and export of meteorites. As always, collectors should respect national laws and work with reputable sources. Pieces of DaG 476 and its paired stones are held by museums and research institutions, where they continue to reveal clues about the geology of Mars.
Did you know?
DaG 476 has several paired stones, found nearby and given their own numbers.
Its large olivine crystals grew in magma before the rest of the rock crystallised.
Desert weathering added carbonate minerals to its cracks, which scientists must separate from Martian features.