Découverte d’une possible météorite terrestre après un long séjour dans l’espace.

Appelée “Northwest Africa (NWA) 13188”, this rock weighing over 600 grams could be the first meteorite to return to Earth after a long stay in space. Scientists have noted a strong resemblance between this rock and those that form in volcanoes near oceanic tectonic plates. The presence of certain chemical isotopes suggests that the rock has been exposed to cosmic rays from space for tens of thousands of years, explain the researchers.

The glassy “fusion crust” of the rock suggests that it melted upon entering Earth’s atmosphere and proves that it is not a “fake meteorite,” said Jérôme Gattacceca, a geophysicist at the National Center for Scientific Research, during the Goldschmidt geochemistry conference in France. “We consider NWA 13188 to be a meteorite ejected from Earth and then returned to the surface,” conclude the authors of the study.

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Scientists are still trying to figure out how this rock could have reached space. For now, they assume that it originated from a strong volcanic eruption or a large meteorite that hit Earth. The team of researchers is studying the volcanic hypothesis. To do this, they are checking the concentrations of atmospheric argon contained in NWA 13188, which should be particularly abundant if the rock originated from a volcanic eruption.

“When you make extraordinary assumptions, you need extraordinary evidence to support them. I’m still not convinced,” said Philippe Claeys, a geologist and planetary scientist. And he added, “When you have such a young impact crater, you would have a still ‘hot and smoky’ impact melt, it would be very difficult to miss it.”