NWA 7034
Nicknamed Black Beauty, this dark Martian breccia contains the oldest pieces of Mars yet found.
Key facts
- Type
- Martian meteorite (polymict regolith breccia)
- Fell or found
- Found
- Year
- 2011 (acquired)
- Country
- Northwest Africa (Sahara; exact site unknown)
- Mass
- about 320 g
- Official name
- Northwest Africa 7034
In 2011, a collector in the United States bought a dark, glossy stone weighing about 320 grams from meteorite dealers in Morocco. It had been found somewhere in the Sahara Desert. Because the exact place of discovery is not known, it was named using the system for meteorites from that region: Northwest Africa, followed by a number. Scientists at the University of New Mexico, led by Carl Agee, studied the stone and found that it was unlike any meteorite they had seen. It was from Mars, but it was not like other Martian meteorites. Its dark, shiny appearance, due partly to fine-grained iron oxide minerals such as magnetite, earned it the nickname Black Beauty.
A different kind of Martian rock
Most Martian meteorites are igneous rocks, formed when molten rock cooled and crystallised, such as the shergottites, nakhlites and chassignites. NWA 7034 is a breccia, a rock made of many different broken pieces cemented together. It contains fragments of various igneous rocks, pieces of older breccias, glassy material and fine-grained matrix. This kind of mixture is typical of regolith, the layer of broken rock and dust on the surface of a planet, churned up by impacts over billions of years.
In other words, Black Beauty is probably a piece of the Martian surface itself: a sample of the soil-like rubble that covered the planet's ancient crust.
Ancient zircons
One of the most exciting discoveries in NWA 7034 and its paired stones (other pieces from the same fall, found separately) is the presence of tiny crystals of the mineral zircon. Zircons are extremely tough and contain uranium, which decays at a known rate, making them excellent natural clocks. Some zircons in Black Beauty have been dated to about 4.4 to 4.5 billion years ago, not long after Mars formed. They are among the oldest known pieces of Mars, giving scientists a rare glimpse of the planet's earliest crust. Several paired stones, given their own Northwest Africa numbers, have since been identified, providing far more material than the original 320-gram stone alone.
More water than expected
Black Beauty also contains more water than most other Martian meteorites, locked into the structure of its minerals rather than present as liquid. Studies suggest that it contains several times, perhaps around ten times, as much water as typical Martian meteorites. This water probably came from interactions with water near the Martian surface, which is consistent with evidence from rovers and orbiters that water once played an important role on Mars.
Where on Mars?
Scientists would love to know exactly where on Mars Black Beauty came from. Researchers have compared its age and composition with craters on the Martian surface to identify possible source regions. Several candidates have been proposed, but the answer is not yet certain. If confirmed, a source region would allow scientists to link the meteorite's laboratory measurements directly to a place seen in spacecraft images.
Why it matters
NWA 7034 changed our picture of Martian meteorites. Before its discovery, all known Martian meteorites were relatively young igneous rocks or a handful of older ones. Black Beauty offered a sample of the ancient, battered surface crust, rich in water and full of fragments dating back to the planet's infancy. It is now one of the most studied Martian meteorites, and pieces of it and its paired stones are held in collections around the world.
It also illustrates the importance of desert finds. Many meteorites from the Sahara are bought and sold before being studied, and their exact find sites are often lost. Careful records, honest dealing and respect for national laws help ensure that such meteorites keep their scientific value.
Did you know?
NWA 7034 is nicknamed Black Beauty because of its dark, glossy appearance.
Zircon crystals in Black Beauty and its paired stones are about 4.4 to 4.5 billion years old.
It contains much more water in its minerals than most other Martian meteorites.