Scientists have long been puzzled over the origins of Martian meteorites found on Earth.
TL;DR
Scientists traced 200 meteorites from Mars to volcanic regions, Tharsis and Elysium, using high-resolution simulations. They pinpointed the craters responsible for launching these rocks into space, revealing the size and depth of the craters. The meteorites provide data about impact pressures and the ejection process, helping researchers estimate when specific events occurred. This research offers detailed information about Mars’ volcanic activity, magma sources, and the formation of impact craters during the Amazonian period, about 3 billion years ago. The findings are based on mineral changes, impact glass, and fracture patterns in the meteorites.
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Debris from Mars has often made its way to Earth, thanks to powerful impacts on the Martian surface that send material into space. At least 10 meteorite-forming events have occurred in Mars’ recent history. These impacts can launch rocks with enough force to escape Mars’ gravity and orbit the sun, with some eventually landing on Earth.
Researchers at the University of Alberta have traced 200 of these meteorites back to five impact craters in two volcanic regions on Mars, known as Tharsis and Elysium. “We can now group these meteorites by their shared history and pinpoint their locations on Mars before they arrived on Earth,” explained Chris Herd, a professor and curator of the university’s meteorite collection.
While meteorites regularly fall to Earth — NASA estimates about 48.5 tons (44,000 kilograms) of material falls daily — most of it arrives as tiny dust particles. Tracing their origins can be challenging, but in the 1980s, scientists noticed a group of meteorites with volcanic characteristics dating back 1.3 billion years. This suggested they came from a body with relatively recent volcanic activity, making Mars the prime suspect. The connection was confirmed when NASA’s Viking landers compared Mars’ atmospheric composition with trapped gases in the meteorites.
Pinpointing the exact origin on Mars has been difficult due to limitations of spectral matching, a method that compares the light absorbed or emitted by materials. This technique is hindered by factors like terrain differences and dust cover, particularly on younger terrains like Tharsis and Elysium. Identifying the source of these meteorites, however, would provide new insights into Mars’ geological history.
“It would help recalibrate Mars’ timeline, shedding light on the timing and nature of key events in its history,” Herd said. “For example, we could determine that a specific meteorite was ejected by an impact event that created craters between 10 and 30 kilometers in diameter.”
The team used high-resolution simulations of impacts on a Mars-like planet. “One of the breakthroughs here is being able to model the ejection process and identify the crater size that could have launched specific meteorites,” Herd explained.
These simulations allowed researchers to measure the shock pressures experienced by the rocks and the duration of exposure, based on shock features like mineral changes, impact glass, and fracture patterns found in the meteorites. From this data, Herd’s team estimated the size of the impact craters and how deep the rocks were buried before the impacts. While these depth estimates are not exact, they were compared to the geology of potential source craters and the characteristics of the meteorites.
“[Our modeling approach] lets us narrow down the possible source craters from 15 to a more precise number based on the meteorites’ features,” Herd said. “This could even allow us to reconstruct the volcanic history of these rocks before they were ejected from Mars.”
This research could offer insights into the timing of volcanic events on Mars, the different sources of Martian magma, and the formation of craters during a period of low meteorite bombardment known as the Amazonian period, which occurred around 3 billion years ago.
“It’s incredible when you think about it,” Herd added. “It’s the closest we can get to going to Mars and collecting a rock ourselves.”
