On the surface, it was just a black rock that had fallen from the sky, sold as a curiosity to a collector in 2011. However, behind its dark exterior lay a secret that had been buried for billions of years. Analysis revealed much more than just its Martian origin.
A unique Martian rock discovered in the Sahara Desert
A mysterious black stone that fell from the sky was discovered in 2011 in the Western Sahara Desert by a group of Sahrawis. Put up for sale, it was quickly acquired by an American collector in Morocco.
Long identified as a fragment of the Martian crust, it took scientists more than a decade to reveal one of its best-kept secrets.
“Black Beauty,” a time capsule from Mars
Officially named Northwest Africa 7034 (NWA 7034), this 320-gram meteorite stands out for its unique composition among known Martian samples. It contains minerals of varying ages, some extremely old and others younger, but its structure corresponds to observations made by NASA rovers on the surface of Mars. These clues confirm that this rock was once part of the Martian crust before being torn from the surface of the Red Planet.
Recent analysis of a tiny grain of zircon extracted from the meteorite has revealed an astonishing age: 4.45 billion years. This relic dates back to the early stages of Martian history, long before the planet became the arid desert we know today. Unlike most Martian meteorites, which originate from more recent geological periods, NWA 7034 offers us a valuable window into the conditions on the surface of Mars in its early days.
Evidence of hot water on Mars
Black Beauty also stands out for its high water content, up to ten times higher than that of other known Martian meteorites. It was already known that the rock had interacted with water on Mars during its formation, but the use of advanced microscopy techniques has revealed a key element: the presence of tiny inclusions of magnetite (an iron oxide) trapped in the zircon.
This discovery suggests that the zircon crystallized in a hydrothermal environment, i.e., in the presence of high-temperature water and under oxidizing conditions. Furthermore, the magnetite is found in areas of the zircon that are unaffected by radiation, indicating that it formed at the same time as the zircon, rather than as a result of subsequent geological processes.
In other words, 4.45 billion years ago, during the pre-Noachian period of Mars, hot water sources already existed in the Martian crust. Black Beauty thus provides direct evidence that water was present on Mars in its early days.
An environment conducive to life?
This discovery reinforces the hypothesis that Mars, very early in its history, had conditions favorable to the emergence of life, at least in microbial form.
The question of whether life existed on Mars or whether it could have been transported to Earth by meteorites remains unanswered, due to a lack of tangible evidence. But the fact that a meteorite discovered in 2011 has provided so much information demonstrates the crucial importance of the Martian samples that NASA and China plan to bring back to Earth in the coming years.
