A black stone that had fallen from the sky was discovered in the Sahara desert by a Saharawi group. Selling to the highest bidder, we have known for a long time that it comes from the Mars cortex, but they have had to spend more than 10 years for scientists to desert one of their best kept secrets.
A meteorite called “Black Beauty”. Officially called Northwest Africa 7034, the 320 grams rock was found in 2011 in the Sahara desert, in Western Sahara, and later sold to an American collector in Morocco.
Its composition is unique among known Martian meteorites. It contains very old and very young minerals glued to each other, but coincides with what was observed by NASA’s rovers on the surface of Mars, so it was part of the Martian cortex when it detached from the red planet.
A time capsule. A recent study focuses on a zircon grain found in the meteorite. This zircon has no less than 4,450 million years, which places it in the earliest stages of Martian history.
The majority of known meteorites that come from Mars are from later geological periods, so NWA 7034 provides invaluable information on what the surface environment of the red planet was long before becoming what it is today.
The meteorite that contains the most water. What makes Black Beauty exceptional is that it houses 10 times more water than other Martian meteorites. It was known that by the interaction of the rock with the water present in the crust of the planet at the time of its formation, but the recent analysis of the zircon with modern microscopy techniques has revealed much more information.
The fragment contains iron, aluminum and sodium, unusual elements for a zircon of purely magmatic origin. But it is above all the presence of tiny inclusions of magnetite (iron oxide) that suggests that it crystallized under hydrothermal conditions. That is, in the presence of water at high temperature, and in an oxidizing environment.
Ancient hot springs. The magnetite is trapped in zones of the zirch that are not altered by radiation, which indicates that they were formed at the same time as the zirch, and not as a result of subsequent secondary processes, the researchers explain.
What the study comes to say is that 4,450 million years ago, during what is known as the pre-ondic period of Mars, there were already hydrothermal conditions in the Martian cortex. The Black Beauty meteorite is a direct proof that Mars had water in its formation stages.
Favorable conditions for life. The finding reinforces the hypothesis that Mars had from very early the necessary conditions to house life, or at least some environments suitable for microbial life.
That there was life on Mars or that it reached the earth through a meteorite are still two hypotheses for which we have no evidence. However, that a meteorite of 2011 has given us so much information and reasons to continue investigating demonstrates how important the Martian samples can be that NASA and China want to bring in the coming years.
Images | New Mexico University, NASA
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