Mars' oldest meteorite traced to strange double impact crater

The meteorite is somewhat older than 4.5 billion years.

Artificial intelligence (AI) has been used by researchers to pinpoint the origin of the oldest known Martian meteorite, and the results may help us understand the early circumstances on the planets of our solar system.

Officially known as Northwest Africa 7034 but more frequently referred to as "Black Beauty," the 11-ounce (320-gram) meteorite is thought to have struck Earth some 5 million years ago. Its age was determined to be just around 4.5 billion years old after it was discovered in the Sahara Desert in 2011, making it the oldest Martian meteorite ever discovered on Earth.

The meteorite, according to scientists, was sent hurtling toward Earth following a strong asteroid collision that tore apart pieces of Mars' crust and shot them into orbit. Researchers have now located Black Beauty's genesis in a tiny crater within a larger crater in the southern hemisphere of Mars after using a machine-learning system to identify and categorize 94 million craters there. The Australian mining community where many of the oldest rocks on Earth have been discovered is whence the geologists got the name Karratha for the crater. On July 12, they published their research in the magazine Nature Communications (opens in new tab).

Finding the area from which the "Black Beauty" meteorite originates is crucial because it contains the oldest Martian fragments ever discovered, dating to 4.48 billion years old, and it demonstrates similarities between the very old crust of Mars, estimated to be 4.53 billion years old, and the continents of the modern Earth. The area that we have determined to be the origin of this particular Martian meteorite sample "constitutes a real window into the earliest environment of the planets, including the Earth, which our planet lost due to plate tectonics and erosion."

Researchers used a machine-learning system to locate the meteorite's origin by feeding it photos of 94 million Martian craters captured by the context camera on board the Mars Reconnaissance Orbiter. The AI compared the size and distribution of the craters with the composition of the stray meteorite, which is one of the most magnetic and has some of the greatest potassium and thorium concentrations of any Martian meteorite discovered on Earth. This reduced the number of potential craters to 19, one of which the researchers chose because it closely matched the timing of the Martian impact and the characteristics of the meteorite.

The researchers discovered that Black Beauty came to Earth as a result of two asteroid crashes by examining the impact crater. Black Beauty and other rocks were violently torn from the Martian crust during the first impact, which roughly 1.5 billion years ago collided with Mars and created the 25-mile-wide (40-kilometer) Khujirt crater. These rocks were then violently launched into space before raining back down onto the surface of the Red Planet. A second impact drove Black Beauty hurtling through space toward Earth after 5 to 10 million years of rest, leaving behind the Karratha crater inside the Khujirt crater.

The results imply that the rock was originally a component of Mars' primordial crust, which formed soon after the Red Planet's lava ocean cooled and hardened. This makes the crater particularly fascinating to scientists who wish to learn how the bodies of our solar system were formed, as plate tectonics destroyed Earth's primordial crust and the original crust of the moon is buried under thousands of meters of moon dust.

The researchers claim that the system may be modified to do comparable searches throughout the moon and Mercury in addition to locating the ejection sites of other Martian meteorites.

In the statement, co-author Gretchen Benedix, a planetary scientist at Curtin University, said, "This will help to unravel their geological history and answer pressing questions that will help future investigations of the Solar System such as the Artemis program to send humans on the Moon by the end of the decade or the BepiColombo mission, in orbit around Mercury in 2025."