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Believe it or not, debris from Mars often makes its way to Earth after powerful impacts hit the Red Planet’s surface and launch it into space.
There have been at least 10 of these meteorite formation events in the recent history of Mars. When these massive impacts occur, meteorites can be ejected from the Red Planet with enough velocity to break free of Mars’ gravitational pull to enter orbit around the sun, and some of them eventually fall to Earth.
Scientists at the University of Alberta have now traced the origin of 200 of these meteorites to five impact craters in two volcanic regions on Mars, known as Tharsis and Elysium. “Now, we can group these meteorites according to their shared history and then their location on the surface prior to their arrival on Earth,” said Chris Herd, curator of the university’s meteorite collection and professor in the Faculty of Science, in his . statement.
Meteorites fall to Earth all the time – an estimated 48.5 tonnes (44,000 kilograms) of meteorite material fall every day, according to NASA – although the majority arrive on the surface as tiny particles of dust that cannot be absorbed. noticed. Their origin is often difficult to determine, but in the 1980s, scientists suspected a group of meteorites that appeared to have a volcanic origin with an age of 1.3 billion years.
This meant that these rocks had to come from a celestial body with recent volcanic activity (in geological terms), making Mars a likely candidate. However, proof came when NASA’s Viking landers were able to compare the composition of Mars’ atmosphere with trapped gases found in these rocks.
It was previously difficult to identify exactly where on Mars they came from. The team noted in their paper that this difficulty arose from using a technique called spectral matching, a technique used to identify and compare the composition of materials by analyzing the patterns of light they absorb or emit. .
However, this method is limited by factors such as terrain variability and extensive dust cover, which can skew spectral signals, especially on younger terrain such as Tharsis and Elysium. But knowing exactly where these Martian meteorites came from would enable scientists to better piece together the planet’s geological history.
“[It would] enabling the recalibration of the chronology of Mars, with implications for the timing, duration and nature of a wide range of major events throughout Mars’ history,” said Herd. The conditions under which this meteorite was ejected were met by an impact event that produced a crater between 10 and 30 kilometers across. “
The team put together high-resolution simulations of impacts in a Mars-like planet. “One of the major advances here is to be able to model the ejection process, and from that process to be able to determine the size of the crater or the range of crater sizes that that particular group of meteorites could eject in the end, or even that particular meteorite,” said Treada.
The output of the model allowed the team to determine the “peak shock pressures” of the impact events and how long the rocks were exposed to those pressures. This can be determined from “shock features” observed in the meteorites – for example, unique mineral changes, impact glass, and special fracture patterns.
From this data, Herd and his colleagues were able to estimate the size of the impact craters the meteorites could have sent, as well as how deep the rocks were buried before the impact. Although these depth estimates have some uncertainty, the researchers compared them to the local geology of the potential source craters and the characteristics and ages of the meteorites to see if they are aligned.
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“[Our modelling approach] lets say, of all these possible craters, we can narrow them down to 15, and then from the 15 we can narrow them down further based on meteorite characteristics,” he said. “We can even the reconstruct volcanic stratigraphy. [the geological record]the position of all these rocks, before they rose from the surface.”
This could help scientists better understand when volcanic events occurred on Mars, the different sources of Martian magma, and how quickly craters formed during an era of low meteorite bombardment on the Red Planet. called the Amazonian period, about 3 billion years ago.
“It’s amazing if you think about it,” said Herd. “The closest thing to us is going to Mars and picking up a rock.”
