Martian meteorite points to late asteroid bombardment

(ORDO NEWS) — Evidence of intense asteroid bombardment shows that young Mars became comfortable enough for life to emerge later than thought.

Australian geologists analyzed samples of the Martian meteorite NWA 7034, finding twin zircon crystals in them – evidence that indicates a powerful impact. Apparently, the heavy asteroid bombardment continued on Mars later than hitherto thought. This means that the Red Planet became potentially habitable also not too early in its history.

Occasionally, fragments of the Martian surface are knocked out by falling bodies into space. Some of them in their journey reach the Earth and fall on it. Today, several hundred such Martian meteorites have been identified, but the 320-gram NWA 7034 stands out from the crowd. It was found in Morocco in 2011 and consists of sharp, angular, rough basalt clasts.

NWA 7034 contains a considerable amount of water carried away from what was apparently wet Mars. And recently, Morgan Cox of Curtin University in Australia discovered 66 zircon particles, among other inclusions , one of which retained evidence of a powerful impact. Its crystals coalesced into twins, so that the adjacent crystal lattices were connected by their planes of symmetry, as if “driven” into one another.

Martian meteorite points to late asteroid bombardment 2

Such twinning of zircon on Earth is found only in places associated with one specific impact: a heavy impact of a meteorite, at a pressure that momentarily reaches 20-40 hectopascals.

Examples of it, in particular, are found in samples from the Chickxulub crater, which formed 66.5 million years ago and is believed to be associated with the Cretaceous-Paleogene mass extinction that wiped out all flightless dinosaurs. The age of the Martian NWA 7034 is estimated at 4.45 billion years, and this forces us to take a closer look at how we imagine the past of the Red Planet.

The young solar system remained full of “construction debris”, the bodies left after the formation of the planets. Therefore, all newborn worlds went through a period of intense bombardment by celestial bodies. It was believed that on Mars it ended about 4.48 billion years ago, and the planet became calm enough and potentially convenient for the emergence of primitive life.

However, the “double” zircon granule indicates a very powerful impact that occurred 30 million years later. This means that a comfortable period for life did not begin here as early as it was assumed so far.

“Mars has been hit by impact bombardment on a scale that has caused mass extinctions on Earth,” says Aaron Cavosie, one of the authors of the paper. “The zircon we have described provides evidence for such impacts and indicates that the opportunity for habitability appeared even later than thought—perhaps around the time that the oldest traces of water on Mars are associated, around 3.9-3.7 billion years ago”.


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