Martian meteorite NWA 7034, otherwise known as "Black Beauty," is not like any other meteorite from the red planet on Earth.
Now scientists think they know why: Black Beauty is the only example of Mars' crust to ever make it to Earth.
Other Martian meteorites we've found on Earth are SNC meteorites, classified as shergottites, nakhlites or chassignites. They're mostly composed of cooled magma and other volcanic material. However, Black Beauty is a breccia, which means its composition contains a variety of rocks, all held together by basalt.
That makes Black Beauty identical to the rock compositions studied by the Mars rovers on the surface of the red planet. This means that Black Beauty is a specimen of Mars' crust. It also clears up earlier confusion about why other Martian meteorites on Earth contained different compositions than those on Mars itself.
Scientists came to their conclusion about Black Beauty after using spectroscopy, including using a new imaging system that allowed them to get full spectral images of their sample of the meteorite.
"Other techniques give us measurements of a dime-sized spot," says Kevin Cannon, the study's lead author. "What we wanted to do was get an average for the entire sample. That overall measurement was what ended up matching the orbital data."
These researchers believe that Black Beauty comes from an area of Mars called the Dark Plains. Here, there is less red dust on the surface of the planet, at least compared to other parts of Mars, and this leaves the crust exposed. It's likely that most of the Dark Plains looks a lot like Black Beauty.
It's also likely that many impacts hitting the planet's surface created this region of Mars. That explains why the meteorite contains so many different rock types.
"Mars is punctured by over 400,000 impact craters greater than 1 km in diameter ...," the researchers write. "Because brecciation is a natural consequence of impacts, it is expected that material similar to NWA 7034 has accumulated on Mars over time."
Black Beauty, discovered a few years ago in the Moroccan desert, is estimated at 4.4 billion years ago, making it the oldest Martian meteorite ever found.
Although we're learning a lot about Mars thanks to the rovers we've sent to the red planet, much of what we now know comes from its meteorites here on Earth. Thanks to studies of these meteorites, we've learned a lot about Martian's atmosphere, along with hints that there was once water on the red planet's surface.
