The oldest crust of Mars lies? The region of origin of an ancient Martian meteorite could contain crustal rocks that are 4.5 billion years old

Primordial crust: In a small crater south of Mars’ equator, the oldest planetary rocks in the Solar System can be exposed. Because one of the oldest known Martian meteorites comes from the Karatha crater, the researchers identified. The meteorite NWA 7034 contains minerals that are 4.5 billion years old. Thus, the ancient crust at the now-identified point of origin could provide insight into the early days of Mars and Earth – it would be a useful landing site for future Mars investigations.

Rocks and minerals from the early days of the solar system provide valuable information about how planets form and grow. But on Earth, tectonic plates have long deepened the rocks of the first crust Drawn in the mantle of the earth. Therefore, there are no longer any unchanged effects of this type of protostox on the Earth’s surface. Different on Mars: Since the Red Planet does not have active tectonic plates, bits of primitive crust can still be preserved on it.

Fragment of a Martian meteorite NWA 7034 (Black Beauty). © NASA

A meteorite with minerals that is approximately 4.5 billion years old

Some Martian meteorites discovered in recent years from the desert attest to the existence of such ancient crust on Mars. These bits, which were ejected from the surface of the Red Planet by collisions and flung toward Earth, contain minerals that date back to the time the planet was formed. The oldest representative of these Martian pieces is the meteorite NWA 7034, also known as “Black Beauty”. Scientists found in it zircon and other minerals up to 4.48 billion years old.

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But da means: Since this meteorite has been ejected from the surface of Mars, bits of the oldest Martian crust can still be preserved — and thus also some of the oldest planetary rocks in the Solar System. “But the region of origin of this unique meteorite and its geological context remain unknown – and thus also the region in which the oldest geological traces on the planet appear,” explain Anthony Lagin of Curtin University in Australia and colleagues.

original hole chase

But now the research team has discovered where this Martian meteorite came from. His composition previously indicated that the piece must have experienced two effects. The first, about 1.5 billion years ago, brought the rock closer to the surface, and the second impact five million years ago threw the meteor into space. In order to search for the location of this event, the team evaluated data from 90 million well impact craters on Mars using an adaptive algorithm.

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In order to search for the crater, the researchers evaluated data from several Mars probes. © Lagain et al./ Nature Communications

Based on the overlap of the hole, the system determined its approximate life. However, among the candidates for a crater of appropriate age, only those whose geological features matched the composition of NWA 7034 were considered for the original site. The crater must therefore be located in a slightly altered ancient region and contain rocks with high concentrations of thorium and potassium and evidence of prior magnetization.

Young hole in the ancient highlands

The search was successful: “Only one crater filter has features that match those of the meteorite,” Lagin and colleagues report. “The geological context of the Karatha crater fits the chronology, petrology and magnetic and chemical signatures of the NWA 7034 meteorite group.”

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The “house” of the meteorite is located south of the Martian equator and west of the large volcanoes of Tharsis on the northeastern edge of the Terra Cimmerian Serenum Plateau (TCTS). “This TCTS region has the thickest crust on the planet,” the researchers said. According to them, the high residual magnetization and the initial formation of these ridges indicate that the surface materials in this region were hardly altered by modern rocks and processes – so they must have been very ancient parts of the Martian crust.

Karatha Crater
The Karatha Crater is the smaller inner crater in an older impact valley in this Mars Reconnaissance orbital image. ©NASA/MRO

The assignment of a Martian meteorite to these heights now confirms this: “The region we identified as the origin of this unique Martian meteorite thus provides insight into the early conditions of Mars,” the team explains. “Exploring the heights of the TCTS can help us decipher the formation and early stages of evolution of Mars and all other terrestrial planets.”

Useful target for future Mars missions

According to Lagain and colleagues, this region west of Mars’ large volcanoes is also a promising target for future Mars missions. “The central rims and ridges of large and well-preserved craters in this region could have particularly interesting rock outcrops,” they explained. “These formations may contain missing geological information about the early evolution of Mars.”

The research team also plans to use their algorithm to determine the origin of other meteorites, including pieces of the Moon and Mercury. This will help decipher their geological history and provide answers for future space missions such as the lunar mission Artemis program or the BepiColombo مهمة mission to Mercury,” says Lagina colleague Gretchen Benedix. (Nature Communications, 2022; doi: 10.1038/s41467-022-31444-8)

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Source: Curtin University

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