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A Martian meteorite could reveal new clues about early conditions on the Red Planet

A meteorite originating from the Martian surface and discovered in 2013 in North Africa could prompt scientists to revise their estimates of when the planet may have been habitable.

(CN) — Early in its history, Mars could have hosted conditions which made it suitable for life, but a new study may cause some experts to push back their timeline for when a warmer, milder Martian surface could have existed.

According to previous estimates, major meteorite impacts on Mars likely declined around 4.48 billion years ago, however new research out of Curtin University in Australia reveals that those impacts may have continued to bombard the planet for roughly another 30 million years. Such an intense and prolonged onslaught could have sterilized the planet by vaporizing liquid water sources and allowing its atmosphere to blow off into space, said the authors of a new study.

Published Wednesday in the journal Science Advances, the study looks at damage to a Martian meteorite discovered in 2013 in Northwest Africa, officially dubbed NWA 7034 but nicknamed “Black Beauty,” to determine when major impacts to the planet’s surface likely declined. The meteorite contains remnants of the earliest Martian crust, making it an extremely valuable source of information for researchers.

The team discovered evidence of high-pressure shock deformation in a 4.45-billion-year-old piece of zircon found in the meteorite, leading them to conclude that these impacts could have persisted for millions of years longer than once thought. The meteorite is described as being a collection of broken fragments of rock and minerals, primarily basalt, which solidified over time. Tiny grains of zircon inside the rock is all the evidence that remains for now of those early meteorite bombardments on the Martian surface.

“This grain is truly a one-off gift from the Red Planet. High-pressure shock deformation has not previously been found in any minerals from Black Beauty,” said Morgan Cox, a PhD candidate from Curtin’s Space Science and Technology Centre in the School of Earth and Planetary Sciences, and lead author of the study. “This discovery of shock damage in a 4.45 billion-year-old Martian zircon provides new evidence of dynamic processes that affected the surface of early Mars."

Using backscattered electron and cathodoluminescence imaging, Cox and her team surveyed a total of 66 zircon grains taken from three meteorites in the NWA 7034 suite. They analyzed the grains to determine their crystallographic orientation and wound up identifying a type of shock damage that only occurs after impacts exerting at least 20 to 30 gigapascals of force.

Cox explained that the same type of shock damage evident in the Martian zircon has been reported from every major impact site known on Earth, including the one in Mexico believed to have killed off the dinosaurs, as well as on the Moon, but hadn’t previously been seen in Martian material. This type of shock damage, called “crystal twinning,” occurs when separate crystals share lattice points and become joined together, which can be caused by two rocks crashing forcefully into one another.

The study provides the first evidence that large-scale meteorite impacts severe enough to reduce the Red Planet’s chances of hosting life may have persisted later than 4.48 billion years ago.

“Prior studies of zircon in Martian meteorites proposed that conditions suitable for life may have existed by 4.2 billion years ago based on the absence of definitive shock damage,” said Dr. Cavosie, a geologist at Curtin University, and co-author of the study. “Mars remained subject to impact bombardment after this time, on the scale known to cause mass extinctions on Earth. The zircon we describe provides evidence of such impacts, and highlights the possibility that the habitability window may have occurred later than previously thought, perhaps coinciding with evidence for liquid water on Mars by 3.9 to 3.7 billion years ago.”

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Categories / Environment, Science

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