Thursday, August 11, 2022

Martian meteorites can teach us about Earth’s origins

What do Mars and Iceland have in common?

Almost 4.5 billion years ago, Mars was believed to have a crust similar to Iceland today. Scientists made this discovery after finding the oldest martian fragments on Earth. The fragments offer information about our planet and could explain why the Earth developed into a planet that sustains a broad diversity of life and Mars did not.

A new study by Northern Arizona University offers new insights into Earth’s past. It details how they found the likely martian origin of the 4.48-billion-year-old meteorite, informally named Black Beauty. Its origin is one of the oldest regions of Mars.

Valerie Payré, a postdoctoral researcher in the Department of Astronomy and Planetary Science, said, “This meteorite recorded the first stage of the evolution of Mars and, by extension, of all terrestrial planets, including the Earth. As the Earth lost its old surface mainly due to plate tectonics, observing such settings in extremely ancient terrains on Mars is a rare window into the ancient Earth surface that we lost a long time ago.”

Scientists searched for the origin of a martian meteorite named NWA—Northwest Africa—7034. This meteorite preserved the early stage of Mars’ history, and its chemistry suggests that Mars once experienced volcanic activity similar to that on Earth. Although it was ejected from the surface of Mars five to 10 million years ago after an asteroid impact, its source region and geological context have remained a mystery.

To pinpoint its origin, scientists studied its chemical and physical properties. They found that it was from Terra Cimmeria-Sirenum, one of the most ancient regions of Mars.

According to scientists, the region might have a surface similar to Earth’s continents. The surface of mars has several impact craters; hence it is difficult to find the right one.

In prior work, Lagain’s team created a crater recognition system that uses high-resolution photos of Mars’ surface to locate tiny impact craters. The algorithm discovered around 90 million craters with a diameter of up to 50 meters. In this study, they could pinpoint the most likely ejection site—the Karratha crater, which had previously unearthed debris from an older crater known as Khujirt.

Lagain said, “For the first time, we know the geological context of the only brecciated Martian sample available on Earth, 10 years before the NASA’s Mars Sample Return mission is set to send back samples collected by the Perseverance rover currently exploring the Jezero crater. This research paved the way to locate the ejection site of other Martian meteorites to create the most exhaustive view of the Red Planet’s geological history.”

Payré said“As of today, Mars’ crust complexity is not understood, and knowing about the origin of these amazing ancient fragments could lead future rover and spatial missions to explore the Terra Sirenum-Cimmeria region that hides the truth of Mars’ evolution and perhaps the Earth’s. This work paves the road to locating the ejection site of other martian meteorites that will provide the most exhaustive view of the geological history of Mars and will answer one of the most intriguing questions: why Mars, now dry and cold, evolved so differently from Earth, a flourishing planet for life?”

Journal Reference:

  1. Lagain, A., Bouley, S., Zanda, B. et al. Early crustal processes revealed by the ejection site of the oldest martian meteorite. Nat Commun 13, 3782 (2022). DOI: 10.1038/s41467-022-31444-8
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