We might have just found the home of the oldest known Martian meteorite, a 4.5-billion-year-old space rock found in the Sahara desert more than a decade ago. With that, we might have gotten a better understanding of how our own planet changed over time as well.
As Earth evolved, part of its geological history has been lost, but there may be very rare clues to its formation and evolution on other terrestrial worlds. Mars presents an accessible and unique example of a similar early evolution path to our own. Scientists are pretty confident of that thanks to excellent samples examined by spacecraft and rovers sent to the Red Planet, as well as Martian meteorites that have made their way to Earth.
The oldest of these Martian samples found on Earth was discovered in northern Africa in 2011. Coined the "Black Beauty" meteorite, it is the most diverse Martian meteorite in terms of composition, containing a variety of igneous, sedimentary, and impact melt clasts.
But up until now, no one knew where exactly this unique meteorite came from and information on its geological background was limited. Now, for the first time ever, many questions about this record-holding meteorite have been answered by researchers at Curtin University -- with the help of an AI.
Researchers have located the precise location of the crater from which the oldest and most famous Martian meteorite was ejected and hurled towards Earth, providing important geological hints about the red planet's early history, as well as that of our own.
The study's lead author, Anthony Lagain from Curtin's Space Science and Technology Centre in the School of Earth and Planetary Sciences, said that the discovery revealed things about the famous Martian meteorite, officially called NWA 7034, that had never been known before. Black Beauty is the only brecciated Martian sample on Earth. This means that it is made up of angular pieces of different types of rock that are stuck together. All other Martian meteorites are made up of only one type of rock.
“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,” Lagain said. “Finding the region where the ‘Black Beauty’ meteorite originates is critical because it contains the oldest Martian fragments ever found, aged at 4.48 billion years old, and it shows similarities between Mars’ very old crust, aged about 4.53 billion years old, and today’s Earth continents.”
To identify the meteorite’s most likely site of origin, the researchers used a machine learning algorithm to analyse the size and distribution of millions of craters on the surface of Mars, which were photographed in high resolution by the Mars Reconnaissance Orbiter’s context camera.
When the scientists looked at the sizes and locations of these craters, they found that most of the smaller ones were scattered around larger ones that were more than 1.8 miles (3 kilometers) wide and less than 10 million years old. Based on these results, it seems likely that these small craters were made by pieces of debris from bigger impacts that fell back to the surface. The fact that all of these craters were made recently (in a geological timeframe) helped explain why the smallest ones could still be seen: erosion and other geological and weather activity on Mars had not yet erased them after millions of years.
Scientists found that 19 craters on Mars -- out of nearly 94 million known craters scattered across the planet --were the most likely places where the meteorites came from. Lagain said that when they compared the properties of these craters to those of NWA 7034, they only found one match. This crater is called Karratha after a city in Australia that has one of the oldest terrestrial rocks on Earth.
The results suggest that the oldest pieces of NWA 7034 were probably dug out of Mars by the cosmic impact that made the 24-mile-wide (40 km) Khujirt crater in the southern hemisphere of Mars 1.5 billion years ago. These ancient pieces, along with the rest of NWA 7034, were blasted off of Mars 5 to 10 million years ago by an impact that formed Karratha crater. Researchers examined high-resolution data on the martian craters using the Curtin HIVE (Hub for Immersive Visualisation and eResearch) and Pawsey Supercomputing Research Center's HIVE, one of the fastest supercomputers in the Southern Hemisphere.
“The region we identify as being the source of this unique Martian meteorite sample constitutes a true window into the earliest environment of the planets, including the Earth, which our planet lost because of plate tectonics and erosion,” Lagain said.
The study was published in the journal Nature Communications.