Martian meteorites hold clues to Earth's origins

It is impossible to know the geological history of the formation of our planet, because it has been destroyed by tectonic movements and the subsequent evolution of the earth’s surface. Or maybe not completely impossible…

There are very rare clues to this process that may be gleaned from pieces of other planets that have arrived at Earth’s surface in the form of meteorites. In particular, Mars can provide an indication of our planet’s early evolutionary path. More than 4.5 billion years ago, Mars probably had a crust similar to that found on early Earth, and information about this crust may be hiding in the oldest Martian meteorites currently known to have landed on Earth.

But first, scientists must identify exactly where the 4.48 billion-year-old meteorite, dubbed Black Beauty, came from on the surface of Mars. Studies published in Nature Communicationdetails the methods the international team used to identify that this piece of Martian rock came from one of the oldest regions on the Martian surface.

“This meteorite records the first stage of the evolution of Mars and, by extension, all the terrestrial planets, including Earth,” said Valerie Payré, a postdoctoral researcher in the Department of Astronomy and Planetary Science at the University of Northern Arizona. “Because Earth lost its old surface mainly due to plate tectonics, observing such a setting in the very ancient terrain of Mars is a rare window into the ancient Earth’s surface that has been lost for a long time.”

The meteorite, officially known as NWA (North West Africa) 7034 for the site of its discovery, consists of a variety of igneous, sedimentary, and impacted clastics, including the oldest and most evolved igneous clastics and zircons, dated 4.44-4.48 Ga. (billion years), roughly the time of the formation of Mars. Although scientists know the details of its chemical composition, the source region of this unique meteorite on Mars remains unknown so far. Given ancient times, it is possible that it was part of the planet’s early crust and thus retains insight into the geological history of the planet.

Previous research, using crater detection algorithms and high-resolution images of the Martian surface, has identified just 18 crater locations where an asteroid strike was strong enough to hurl NWA 7034 far enough from the Martian surface to enter space and begin its journey to Earth’s surface.

The current research, led by Anthony Lagain of Curtin University in Australia, uses the geochemical and geophysical properties of the ancient meteorite, along with its geochronology, to identify which craters could potentially be the origin of this part of Mars. They found only one candidate – the Karratha crater – that matched the meteorite’s unique combination of magnetic field intensity, high concentrations of potassium and thorium, and dating details. Furthermore, the experts concluded that when the asteroid that formed this crater hit the Martian surface, it ejected other debris, including NWA 7034, which lay on the surface as a result of a much earlier impact that had formed an older crater called Khujirt. .

Both craters are found in a region known as Terra Cimmeria-Sirenum, a high-altitude region that covers about 10 percent of the planet, where there are high concentrations of the elements potassium and thorium, and high magnetic field intensity. This is one of the most ancient regions of Mars, thought to represent ancient crustal blocks, and it is possible that the Black Beauty was actually part of the planet’s early geological history.

“For the first time, we know the geological context of the only brecciated Martian sample available on Earth, 10 years before NASA’s Mars Sample Return mission is set to send back samples collected by the Perseverance rover currently exploring the Jezero crater,” Lagain said. . , a researcher in the School of Earth and Planetary Sciences at Curtin. “This research paves the way for finding the location of the ejection of other Martian meteorites, in order to create the most complete view of the geological history of the Red Planet.”

Payré studied the nature and formation of the Martian crust to determine whether Earth and Mars had a common past that included crusts such as continents and oceans. He used orbital observations captured in this region to investigate whether traces of similar volcanism found in Iceland exist on Mars.

“To this day, the complexity of Mars’ crust is not understood, and knowing about the origins of these fascinating ancient fragments could direct future explorers and spatial missions to explore the Terra Sirenum-Cimmeria region that hides the truth of the evolution of Mars, and possibly Earth,” Payré said.

“This work paves the way for discovering the location of other Martian meteorite ejections that will provide the most complete view of Mars’ geological history and will answer one of the most interesting questions: why did Mars, now dry and cold, evolve so differently from Earth, the planet that evolved to form a planet. life.”

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By Alison Bosman, Earth.com Writing Staff

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